[PATCH v9 0/6] MTE support for KVM guest

[PATCH v9 0/6] MTE support for KVM guest

[Steven Price]

This series adds support for using the Arm Memory Tagging Extensions
(MTE) in a KVM guest.

This version is rebased on v5.12-rc1 and added a documentation patch,
but is otherwise unchanged from the v8[1] posting.

Changes since v8[1]:
 * Rebased on v5.12-rc1 (note new CAP number)
 * New documentation patch

[1] https://lore.kernel.org/r/20210205135803.48321-1-steven.price@arm.com/

Steven Price (6):
  arm64: mte: Sync tags for pages where PTE is untagged
  arm64: kvm: Introduce MTE VM feature
  arm64: kvm: Save/restore MTE registers
  arm64: kvm: Expose KVM_ARM_CAP_MTE
  KVM: arm64: ioctl to fetch/store tags in a guest
  KVM: arm64: Document MTE capability and ioctl

 Documentation/virt/kvm/api.rst             | 37 ++++++++++++
 arch/arm64/include/asm/kvm_emulate.h       |  3 +
 arch/arm64/include/asm/kvm_host.h          |  9 +++
 arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
 arch/arm64/include/asm/pgtable.h           |  2 +-
 arch/arm64/include/asm/sysreg.h            |  3 +-
 arch/arm64/include/uapi/asm/kvm.h          | 13 +++++
 arch/arm64/kernel/asm-offsets.c            |  3 +
 arch/arm64/kernel/mte.c                    | 16 ++++--
 arch/arm64/kvm/arm.c                       | 66 ++++++++++++++++++++++
 arch/arm64/kvm/hyp/entry.S                 |  7 +++
 arch/arm64/kvm/hyp/exception.c             |  3 +-
 arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
 arch/arm64/kvm/mmu.c                       | 16 ++++++
 arch/arm64/kvm/sys_regs.c                  | 28 +++++++--
 include/uapi/linux/kvm.h                   |  2 +
 16 files changed, 283 insertions(+), 12 deletions(-)
 create mode 100644 arch/arm64/include/asm/kvm_mte.h

-- 
2.20.1

[PATCH v9 0/6] MTE support for KVM guest

[Steven Price]

This series adds support for using the Arm Memory Tagging Extensions
(MTE) in a KVM guest.

This version is rebased on v5.12-rc1 and added a documentation patch,
but is otherwise unchanged from the v8[1] posting.

Changes since v8[1]:
 * Rebased on v5.12-rc1 (note new CAP number)
 * New documentation patch

[1] https://lore.kernel.org/r/20210205135803.48321-1-steven.price@arm.com/

Steven Price (6):
  arm64: mte: Sync tags for pages where PTE is untagged
  arm64: kvm: Introduce MTE VM feature
  arm64: kvm: Save/restore MTE registers
  arm64: kvm: Expose KVM_ARM_CAP_MTE
  KVM: arm64: ioctl to fetch/store tags in a guest
  KVM: arm64: Document MTE capability and ioctl

 Documentation/virt/kvm/api.rst             | 37 ++++++++++++
 arch/arm64/include/asm/kvm_emulate.h       |  3 +
 arch/arm64/include/asm/kvm_host.h          |  9 +++
 arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
 arch/arm64/include/asm/pgtable.h           |  2 +-
 arch/arm64/include/asm/sysreg.h            |  3 +-
 arch/arm64/include/uapi/asm/kvm.h          | 13 +++++
 arch/arm64/kernel/asm-offsets.c            |  3 +
 arch/arm64/kernel/mte.c                    | 16 ++++--
 arch/arm64/kvm/arm.c                       | 66 ++++++++++++++++++++++
 arch/arm64/kvm/hyp/entry.S                 |  7 +++
 arch/arm64/kvm/hyp/exception.c             |  3 +-
 arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
 arch/arm64/kvm/mmu.c                       | 16 ++++++
 arch/arm64/kvm/sys_regs.c                  | 28 +++++++--
 include/uapi/linux/kvm.h                   |  2 +
 16 files changed, 283 insertions(+), 12 deletions(-)
 create mode 100644 arch/arm64/include/asm/kvm_mte.h

-- 
2.20.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v9 0/6] MTE support for KVM guest

[Steven Price]

This series adds support for using the Arm Memory Tagging Extensions
(MTE) in a KVM guest.

This version is rebased on v5.12-rc1 and added a documentation patch,
but is otherwise unchanged from the v8[1] posting.

Changes since v8[1]:
 * Rebased on v5.12-rc1 (note new CAP number)
 * New documentation patch

[1] https://lore.kernel.org/r/20210205135803.48321-1-steven.price@arm.com/

Steven Price (6):
  arm64: mte: Sync tags for pages where PTE is untagged
  arm64: kvm: Introduce MTE VM feature
  arm64: kvm: Save/restore MTE registers
  arm64: kvm: Expose KVM_ARM_CAP_MTE
  KVM: arm64: ioctl to fetch/store tags in a guest
  KVM: arm64: Document MTE capability and ioctl

 Documentation/virt/kvm/api.rst             | 37 ++++++++++++
 arch/arm64/include/asm/kvm_emulate.h       |  3 +
 arch/arm64/include/asm/kvm_host.h          |  9 +++
 arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
 arch/arm64/include/asm/pgtable.h           |  2 +-
 arch/arm64/include/asm/sysreg.h            |  3 +-
 arch/arm64/include/uapi/asm/kvm.h          | 13 +++++
 arch/arm64/kernel/asm-offsets.c            |  3 +
 arch/arm64/kernel/mte.c                    | 16 ++++--
 arch/arm64/kvm/arm.c                       | 66 ++++++++++++++++++++++
 arch/arm64/kvm/hyp/entry.S                 |  7 +++
 arch/arm64/kvm/hyp/exception.c             |  3 +-
 arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
 arch/arm64/kvm/mmu.c                       | 16 ++++++
 arch/arm64/kvm/sys_regs.c                  | 28 +++++++--
 include/uapi/linux/kvm.h                   |  2 +
 16 files changed, 283 insertions(+), 12 deletions(-)
 create mode 100644 arch/arm64/include/asm/kvm_mte.h

-- 
2.20.1

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

[PATCH v9 0/6] MTE support for KVM guest

[Steven Price]

This series adds support for using the Arm Memory Tagging Extensions
(MTE) in a KVM guest.

This version is rebased on v5.12-rc1 and added a documentation patch,
but is otherwise unchanged from the v8[1] posting.

Changes since v8[1]:
 * Rebased on v5.12-rc1 (note new CAP number)
 * New documentation patch

[1] https://lore.kernel.org/r/20210205135803.48321-1-steven.price@arm.com/

Steven Price (6):
  arm64: mte: Sync tags for pages where PTE is untagged
  arm64: kvm: Introduce MTE VM feature
  arm64: kvm: Save/restore MTE registers
  arm64: kvm: Expose KVM_ARM_CAP_MTE
  KVM: arm64: ioctl to fetch/store tags in a guest
  KVM: arm64: Document MTE capability and ioctl

 Documentation/virt/kvm/api.rst             | 37 ++++++++++++
 arch/arm64/include/asm/kvm_emulate.h       |  3 +
 arch/arm64/include/asm/kvm_host.h          |  9 +++
 arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
 arch/arm64/include/asm/pgtable.h           |  2 +-
 arch/arm64/include/asm/sysreg.h            |  3 +-
 arch/arm64/include/uapi/asm/kvm.h          | 13 +++++
 arch/arm64/kernel/asm-offsets.c            |  3 +
 arch/arm64/kernel/mte.c                    | 16 ++++--
 arch/arm64/kvm/arm.c                       | 66 ++++++++++++++++++++++
 arch/arm64/kvm/hyp/entry.S                 |  7 +++
 arch/arm64/kvm/hyp/exception.c             |  3 +-
 arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
 arch/arm64/kvm/mmu.c                       | 16 ++++++
 arch/arm64/kvm/sys_regs.c                  | 28 +++++++--
 include/uapi/linux/kvm.h                   |  2 +
 16 files changed, 283 insertions(+), 12 deletions(-)
 create mode 100644 arch/arm64/include/asm/kvm_mte.h

-- 
2.20.1

[PATCH v9 1/6] arm64: mte: Sync tags for pages where PTE is untagged

[Steven Price]

A KVM guest could store tags in a page even if the VMM hasn't mapped
the page with PROT_MTE. So when restoring pages from swap we will
need to check to see if there are any saved tags even if !pte_tagged().

However don't check pages which are !pte_valid_user() as these will
not have been swapped out.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/pgtable.h |  2 +-
 arch/arm64/kernel/mte.c          | 16 ++++++++++++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index e17b96d0e4b5..84166625c989 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -312,7 +312,7 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
 		__sync_icache_dcache(pte);
 
 	if (system_supports_mte() &&
-	    pte_present(pte) && pte_tagged(pte) && !pte_special(pte))
+	    pte_present(pte) && pte_valid_user(pte) && !pte_special(pte))
 		mte_sync_tags(ptep, pte);
 
 	__check_racy_pte_update(mm, ptep, pte);
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index b3c70a612c7a..e016ab57ea36 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -26,17 +26,23 @@ u64 gcr_kernel_excl __ro_after_init;
 
 static bool report_fault_once = true;
 
-static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap)
+static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap,
+			       bool pte_is_tagged)
 {
 	pte_t old_pte = READ_ONCE(*ptep);
 
 	if (check_swap && is_swap_pte(old_pte)) {
 		swp_entry_t entry = pte_to_swp_entry(old_pte);
 
-		if (!non_swap_entry(entry) && mte_restore_tags(entry, page))
+		if (!non_swap_entry(entry) && mte_restore_tags(entry, page)) {
+			set_bit(PG_mte_tagged, &page->flags);
 			return;
+		}
 	}
 
+	if (!pte_is_tagged || test_and_set_bit(PG_mte_tagged, &page->flags))
+		return;
+
 	page_kasan_tag_reset(page);
 	/*
 	 * We need smp_wmb() in between setting the flags and clearing the
@@ -54,11 +60,13 @@ void mte_sync_tags(pte_t *ptep, pte_t pte)
 	struct page *page = pte_page(pte);
 	long i, nr_pages = compound_nr(page);
 	bool check_swap = nr_pages == 1;
+	bool pte_is_tagged = pte_tagged(pte);
 
 	/* if PG_mte_tagged is set, tags have already been initialised */
 	for (i = 0; i < nr_pages; i++, page++) {
-		if (!test_and_set_bit(PG_mte_tagged, &page->flags))
-			mte_sync_page_tags(page, ptep, check_swap);
+		if (!test_bit(PG_mte_tagged, &page->flags))
+			mte_sync_page_tags(page, ptep, check_swap,
+					   pte_is_tagged);
 	}
 }
 
-- 
2.20.1

[PATCH v9 1/6] arm64: mte: Sync tags for pages where PTE is untagged

[Steven Price]

A KVM guest could store tags in a page even if the VMM hasn't mapped
the page with PROT_MTE. So when restoring pages from swap we will
need to check to see if there are any saved tags even if !pte_tagged().

However don't check pages which are !pte_valid_user() as these will
not have been swapped out.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/pgtable.h |  2 +-
 arch/arm64/kernel/mte.c          | 16 ++++++++++++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index e17b96d0e4b5..84166625c989 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -312,7 +312,7 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
 		__sync_icache_dcache(pte);
 
 	if (system_supports_mte() &&
-	    pte_present(pte) && pte_tagged(pte) && !pte_special(pte))
+	    pte_present(pte) && pte_valid_user(pte) && !pte_special(pte))
 		mte_sync_tags(ptep, pte);
 
 	__check_racy_pte_update(mm, ptep, pte);
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index b3c70a612c7a..e016ab57ea36 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -26,17 +26,23 @@ u64 gcr_kernel_excl __ro_after_init;
 
 static bool report_fault_once = true;
 
-static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap)
+static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap,
+			       bool pte_is_tagged)
 {
 	pte_t old_pte = READ_ONCE(*ptep);
 
 	if (check_swap && is_swap_pte(old_pte)) {
 		swp_entry_t entry = pte_to_swp_entry(old_pte);
 
-		if (!non_swap_entry(entry) && mte_restore_tags(entry, page))
+		if (!non_swap_entry(entry) && mte_restore_tags(entry, page)) {
+			set_bit(PG_mte_tagged, &page->flags);
 			return;
+		}
 	}
 
+	if (!pte_is_tagged || test_and_set_bit(PG_mte_tagged, &page->flags))
+		return;
+
 	page_kasan_tag_reset(page);
 	/*
 	 * We need smp_wmb() in between setting the flags and clearing the
@@ -54,11 +60,13 @@ void mte_sync_tags(pte_t *ptep, pte_t pte)
 	struct page *page = pte_page(pte);
 	long i, nr_pages = compound_nr(page);
 	bool check_swap = nr_pages == 1;
+	bool pte_is_tagged = pte_tagged(pte);
 
 	/* if PG_mte_tagged is set, tags have already been initialised */
 	for (i = 0; i < nr_pages; i++, page++) {
-		if (!test_and_set_bit(PG_mte_tagged, &page->flags))
-			mte_sync_page_tags(page, ptep, check_swap);
+		if (!test_bit(PG_mte_tagged, &page->flags))
+			mte_sync_page_tags(page, ptep, check_swap,
+					   pte_is_tagged);
 	}
 }
 
-- 
2.20.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v9 1/6] arm64: mte: Sync tags for pages where PTE is untagged

[Steven Price]

A KVM guest could store tags in a page even if the VMM hasn't mapped
the page with PROT_MTE. So when restoring pages from swap we will
need to check to see if there are any saved tags even if !pte_tagged().

However don't check pages which are !pte_valid_user() as these will
not have been swapped out.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/pgtable.h |  2 +-
 arch/arm64/kernel/mte.c          | 16 ++++++++++++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index e17b96d0e4b5..84166625c989 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -312,7 +312,7 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
 		__sync_icache_dcache(pte);
 
 	if (system_supports_mte() &&
-	    pte_present(pte) && pte_tagged(pte) && !pte_special(pte))
+	    pte_present(pte) && pte_valid_user(pte) && !pte_special(pte))
 		mte_sync_tags(ptep, pte);
 
 	__check_racy_pte_update(mm, ptep, pte);
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index b3c70a612c7a..e016ab57ea36 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -26,17 +26,23 @@ u64 gcr_kernel_excl __ro_after_init;
 
 static bool report_fault_once = true;
 
-static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap)
+static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap,
+			       bool pte_is_tagged)
 {
 	pte_t old_pte = READ_ONCE(*ptep);
 
 	if (check_swap && is_swap_pte(old_pte)) {
 		swp_entry_t entry = pte_to_swp_entry(old_pte);
 
-		if (!non_swap_entry(entry) && mte_restore_tags(entry, page))
+		if (!non_swap_entry(entry) && mte_restore_tags(entry, page)) {
+			set_bit(PG_mte_tagged, &page->flags);
 			return;
+		}
 	}
 
+	if (!pte_is_tagged || test_and_set_bit(PG_mte_tagged, &page->flags))
+		return;
+
 	page_kasan_tag_reset(page);
 	/*
 	 * We need smp_wmb() in between setting the flags and clearing the
@@ -54,11 +60,13 @@ void mte_sync_tags(pte_t *ptep, pte_t pte)
 	struct page *page = pte_page(pte);
 	long i, nr_pages = compound_nr(page);
 	bool check_swap = nr_pages == 1;
+	bool pte_is_tagged = pte_tagged(pte);
 
 	/* if PG_mte_tagged is set, tags have already been initialised */
 	for (i = 0; i < nr_pages; i++, page++) {
-		if (!test_and_set_bit(PG_mte_tagged, &page->flags))
-			mte_sync_page_tags(page, ptep, check_swap);
+		if (!test_bit(PG_mte_tagged, &page->flags))
+			mte_sync_page_tags(page, ptep, check_swap,
+					   pte_is_tagged);
 	}
 }
 
-- 
2.20.1

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

[PATCH v9 1/6] arm64: mte: Sync tags for pages where PTE is untagged

[Steven Price]

A KVM guest could store tags in a page even if the VMM hasn't mapped
the page with PROT_MTE. So when restoring pages from swap we will
need to check to see if there are any saved tags even if !pte_tagged().

However don't check pages which are !pte_valid_user() as these will
not have been swapped out.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/pgtable.h |  2 +-
 arch/arm64/kernel/mte.c          | 16 ++++++++++++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index e17b96d0e4b5..84166625c989 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -312,7 +312,7 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
 		__sync_icache_dcache(pte);
 
 	if (system_supports_mte() &&
-	    pte_present(pte) && pte_tagged(pte) && !pte_special(pte))
+	    pte_present(pte) && pte_valid_user(pte) && !pte_special(pte))
 		mte_sync_tags(ptep, pte);
 
 	__check_racy_pte_update(mm, ptep, pte);
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index b3c70a612c7a..e016ab57ea36 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -26,17 +26,23 @@ u64 gcr_kernel_excl __ro_after_init;
 
 static bool report_fault_once = true;
 
-static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap)
+static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap,
+			       bool pte_is_tagged)
 {
 	pte_t old_pte = READ_ONCE(*ptep);
 
 	if (check_swap && is_swap_pte(old_pte)) {
 		swp_entry_t entry = pte_to_swp_entry(old_pte);
 
-		if (!non_swap_entry(entry) && mte_restore_tags(entry, page))
+		if (!non_swap_entry(entry) && mte_restore_tags(entry, page)) {
+			set_bit(PG_mte_tagged, &page->flags);
 			return;
+		}
 	}
 
+	if (!pte_is_tagged || test_and_set_bit(PG_mte_tagged, &page->flags))
+		return;
+
 	page_kasan_tag_reset(page);
 	/*
 	 * We need smp_wmb() in between setting the flags and clearing the
@@ -54,11 +60,13 @@ void mte_sync_tags(pte_t *ptep, pte_t pte)
 	struct page *page = pte_page(pte);
 	long i, nr_pages = compound_nr(page);
 	bool check_swap = nr_pages == 1;
+	bool pte_is_tagged = pte_tagged(pte);
 
 	/* if PG_mte_tagged is set, tags have already been initialised */
 	for (i = 0; i < nr_pages; i++, page++) {
-		if (!test_and_set_bit(PG_mte_tagged, &page->flags))
-			mte_sync_page_tags(page, ptep, check_swap);
+		if (!test_bit(PG_mte_tagged, &page->flags))
+			mte_sync_page_tags(page, ptep, check_swap,
+					   pte_is_tagged);
 	}
 }
 
-- 
2.20.1

[PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature

[Steven Price]

Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
for a VM. This will expose the feature to the guest and automatically
tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
storage) to ensure that the guest cannot see stale tags, and so that
the tags are correctly saved/restored across swap.

Actually exposing the new capability to user space happens in a later
patch.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/kvm_emulate.h |  3 +++
 arch/arm64/include/asm/kvm_host.h    |  3 +++
 arch/arm64/kvm/hyp/exception.c       |  3 ++-
 arch/arm64/kvm/mmu.c                 | 16 ++++++++++++++++
 arch/arm64/kvm/sys_regs.c            |  3 ++-
 include/uapi/linux/kvm.h             |  1 +
 6 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index f612c090f2e4..6bf776c2399c 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
 	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
 	    vcpu_el1_is_32bit(vcpu))
 		vcpu->arch.hcr_el2 |= HCR_TID2;
+
+	if (kvm_has_mte(vcpu->kvm))
+		vcpu->arch.hcr_el2 |= HCR_ATA;
 }
 
 static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 3d10e6527f7d..1170ee137096 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -132,6 +132,8 @@ struct kvm_arch {
 
 	u8 pfr0_csv2;
 	u8 pfr0_csv3;
+	/* Memory Tagging Extension enabled for the guest */
+	bool mte_enabled;
 };
 
 struct kvm_vcpu_fault_info {
@@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
 #define kvm_arm_vcpu_sve_finalized(vcpu) \
 	((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
 
+#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
 #define kvm_vcpu_has_pmu(vcpu)					\
 	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
 
diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
index 73629094f903..56426565600c 100644
--- a/arch/arm64/kvm/hyp/exception.c
+++ b/arch/arm64/kvm/hyp/exception.c
@@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
 	new |= (old & PSR_C_BIT);
 	new |= (old & PSR_V_BIT);
 
-	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
+	if (kvm_has_mte(vcpu->kvm))
+		new |= PSR_TCO_BIT;
 
 	new |= (old & PSR_DIT_BIT);
 
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 77cb2d28f2a4..fdb6ab604fd0 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (vma_pagesize == PAGE_SIZE && !force_pte)
 		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
 							   &pfn, &fault_ipa);
+
+	if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
+		/*
+		 * VM will be able to see the page's tags, so we must ensure
+		 * they have been initialised. if PG_mte_tagged is set, tags
+		 * have already been initialised.
+		 */
+		struct page *page = pfn_to_page(pfn);
+		unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
+
+		for (i = 0; i < nr_pages; i++, page++) {
+			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
+				mte_clear_page_tags(page_address(page));
+		}
+	}
+
 	if (writable)
 		prot |= KVM_PGTABLE_PROT_W;
 
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 4f2f1e3145de..e09dbc00b0a2 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
 		val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
 		break;
 	case SYS_ID_AA64PFR1_EL1:
-		val &= ~FEATURE(ID_AA64PFR1_MTE);
+		if (!kvm_has_mte(vcpu->kvm))
+			val &= ~FEATURE(ID_AA64PFR1_MTE);
 		break;
 	case SYS_ID_AA64ISAR1_EL1:
 		if (!vcpu_has_ptrauth(vcpu))
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 8b281f722e5b..05618a4abf7e 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_DIRTY_LOG_RING 192
 #define KVM_CAP_X86_BUS_LOCK_EXIT 193
 #define KVM_CAP_PPC_DAWR1 194
+#define KVM_CAP_ARM_MTE 195
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.20.1

[PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature

[Steven Price]

Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
for a VM. This will expose the feature to the guest and automatically
tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
storage) to ensure that the guest cannot see stale tags, and so that
the tags are correctly saved/restored across swap.

Actually exposing the new capability to user space happens in a later
patch.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/kvm_emulate.h |  3 +++
 arch/arm64/include/asm/kvm_host.h    |  3 +++
 arch/arm64/kvm/hyp/exception.c       |  3 ++-
 arch/arm64/kvm/mmu.c                 | 16 ++++++++++++++++
 arch/arm64/kvm/sys_regs.c            |  3 ++-
 include/uapi/linux/kvm.h             |  1 +
 6 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index f612c090f2e4..6bf776c2399c 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
 	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
 	    vcpu_el1_is_32bit(vcpu))
 		vcpu->arch.hcr_el2 |= HCR_TID2;
+
+	if (kvm_has_mte(vcpu->kvm))
+		vcpu->arch.hcr_el2 |= HCR_ATA;
 }
 
 static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 3d10e6527f7d..1170ee137096 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -132,6 +132,8 @@ struct kvm_arch {
 
 	u8 pfr0_csv2;
 	u8 pfr0_csv3;
+	/* Memory Tagging Extension enabled for the guest */
+	bool mte_enabled;
 };
 
 struct kvm_vcpu_fault_info {
@@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
 #define kvm_arm_vcpu_sve_finalized(vcpu) \
 	((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
 
+#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
 #define kvm_vcpu_has_pmu(vcpu)					\
 	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
 
diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
index 73629094f903..56426565600c 100644
--- a/arch/arm64/kvm/hyp/exception.c
+++ b/arch/arm64/kvm/hyp/exception.c
@@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
 	new |= (old & PSR_C_BIT);
 	new |= (old & PSR_V_BIT);
 
-	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
+	if (kvm_has_mte(vcpu->kvm))
+		new |= PSR_TCO_BIT;
 
 	new |= (old & PSR_DIT_BIT);
 
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 77cb2d28f2a4..fdb6ab604fd0 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (vma_pagesize == PAGE_SIZE && !force_pte)
 		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
 							   &pfn, &fault_ipa);
+
+	if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
+		/*
+		 * VM will be able to see the page's tags, so we must ensure
+		 * they have been initialised. if PG_mte_tagged is set, tags
+		 * have already been initialised.
+		 */
+		struct page *page = pfn_to_page(pfn);
+		unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
+
+		for (i = 0; i < nr_pages; i++, page++) {
+			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
+				mte_clear_page_tags(page_address(page));
+		}
+	}
+
 	if (writable)
 		prot |= KVM_PGTABLE_PROT_W;
 
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 4f2f1e3145de..e09dbc00b0a2 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
 		val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
 		break;
 	case SYS_ID_AA64PFR1_EL1:
-		val &= ~FEATURE(ID_AA64PFR1_MTE);
+		if (!kvm_has_mte(vcpu->kvm))
+			val &= ~FEATURE(ID_AA64PFR1_MTE);
 		break;
 	case SYS_ID_AA64ISAR1_EL1:
 		if (!vcpu_has_ptrauth(vcpu))
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 8b281f722e5b..05618a4abf7e 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_DIRTY_LOG_RING 192
 #define KVM_CAP_X86_BUS_LOCK_EXIT 193
 #define KVM_CAP_PPC_DAWR1 194
+#define KVM_CAP_ARM_MTE 195
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.20.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature

[Steven Price]

Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
for a VM. This will expose the feature to the guest and automatically
tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
storage) to ensure that the guest cannot see stale tags, and so that
the tags are correctly saved/restored across swap.

Actually exposing the new capability to user space happens in a later
patch.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/kvm_emulate.h |  3 +++
 arch/arm64/include/asm/kvm_host.h    |  3 +++
 arch/arm64/kvm/hyp/exception.c       |  3 ++-
 arch/arm64/kvm/mmu.c                 | 16 ++++++++++++++++
 arch/arm64/kvm/sys_regs.c            |  3 ++-
 include/uapi/linux/kvm.h             |  1 +
 6 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index f612c090f2e4..6bf776c2399c 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
 	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
 	    vcpu_el1_is_32bit(vcpu))
 		vcpu->arch.hcr_el2 |= HCR_TID2;
+
+	if (kvm_has_mte(vcpu->kvm))
+		vcpu->arch.hcr_el2 |= HCR_ATA;
 }
 
 static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 3d10e6527f7d..1170ee137096 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -132,6 +132,8 @@ struct kvm_arch {
 
 	u8 pfr0_csv2;
 	u8 pfr0_csv3;
+	/* Memory Tagging Extension enabled for the guest */
+	bool mte_enabled;
 };
 
 struct kvm_vcpu_fault_info {
@@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
 #define kvm_arm_vcpu_sve_finalized(vcpu) \
 	((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
 
+#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
 #define kvm_vcpu_has_pmu(vcpu)					\
 	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
 
diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
index 73629094f903..56426565600c 100644
--- a/arch/arm64/kvm/hyp/exception.c
+++ b/arch/arm64/kvm/hyp/exception.c
@@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
 	new |= (old & PSR_C_BIT);
 	new |= (old & PSR_V_BIT);
 
-	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
+	if (kvm_has_mte(vcpu->kvm))
+		new |= PSR_TCO_BIT;
 
 	new |= (old & PSR_DIT_BIT);
 
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 77cb2d28f2a4..fdb6ab604fd0 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (vma_pagesize == PAGE_SIZE && !force_pte)
 		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
 							   &pfn, &fault_ipa);
+
+	if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
+		/*
+		 * VM will be able to see the page's tags, so we must ensure
+		 * they have been initialised. if PG_mte_tagged is set, tags
+		 * have already been initialised.
+		 */
+		struct page *page = pfn_to_page(pfn);
+		unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
+
+		for (i = 0; i < nr_pages; i++, page++) {
+			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
+				mte_clear_page_tags(page_address(page));
+		}
+	}
+
 	if (writable)
 		prot |= KVM_PGTABLE_PROT_W;
 
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 4f2f1e3145de..e09dbc00b0a2 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
 		val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
 		break;
 	case SYS_ID_AA64PFR1_EL1:
-		val &= ~FEATURE(ID_AA64PFR1_MTE);
+		if (!kvm_has_mte(vcpu->kvm))
+			val &= ~FEATURE(ID_AA64PFR1_MTE);
 		break;
 	case SYS_ID_AA64ISAR1_EL1:
 		if (!vcpu_has_ptrauth(vcpu))
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 8b281f722e5b..05618a4abf7e 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_DIRTY_LOG_RING 192
 #define KVM_CAP_X86_BUS_LOCK_EXIT 193
 #define KVM_CAP_PPC_DAWR1 194
+#define KVM_CAP_ARM_MTE 195
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.20.1

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

[PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature

[Steven Price]

Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
for a VM. This will expose the feature to the guest and automatically
tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
storage) to ensure that the guest cannot see stale tags, and so that
the tags are correctly saved/restored across swap.

Actually exposing the new capability to user space happens in a later
patch.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/kvm_emulate.h |  3 +++
 arch/arm64/include/asm/kvm_host.h    |  3 +++
 arch/arm64/kvm/hyp/exception.c       |  3 ++-
 arch/arm64/kvm/mmu.c                 | 16 ++++++++++++++++
 arch/arm64/kvm/sys_regs.c            |  3 ++-
 include/uapi/linux/kvm.h             |  1 +
 6 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index f612c090f2e4..6bf776c2399c 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
 	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
 	    vcpu_el1_is_32bit(vcpu))
 		vcpu->arch.hcr_el2 |= HCR_TID2;
+
+	if (kvm_has_mte(vcpu->kvm))
+		vcpu->arch.hcr_el2 |= HCR_ATA;
 }
 
 static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 3d10e6527f7d..1170ee137096 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -132,6 +132,8 @@ struct kvm_arch {
 
 	u8 pfr0_csv2;
 	u8 pfr0_csv3;
+	/* Memory Tagging Extension enabled for the guest */
+	bool mte_enabled;
 };
 
 struct kvm_vcpu_fault_info {
@@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
 #define kvm_arm_vcpu_sve_finalized(vcpu) \
 	((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
 
+#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
 #define kvm_vcpu_has_pmu(vcpu)					\
 	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
 
diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
index 73629094f903..56426565600c 100644
--- a/arch/arm64/kvm/hyp/exception.c
+++ b/arch/arm64/kvm/hyp/exception.c
@@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
 	new |= (old & PSR_C_BIT);
 	new |= (old & PSR_V_BIT);
 
-	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
+	if (kvm_has_mte(vcpu->kvm))
+		new |= PSR_TCO_BIT;
 
 	new |= (old & PSR_DIT_BIT);
 
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 77cb2d28f2a4..fdb6ab604fd0 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (vma_pagesize == PAGE_SIZE && !force_pte)
 		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
 							   &pfn, &fault_ipa);
+
+	if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
+		/*
+		 * VM will be able to see the page's tags, so we must ensure
+		 * they have been initialised. if PG_mte_tagged is set, tags
+		 * have already been initialised.
+		 */
+		struct page *page = pfn_to_page(pfn);
+		unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
+
+		for (i = 0; i < nr_pages; i++, page++) {
+			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
+				mte_clear_page_tags(page_address(page));
+		}
+	}
+
 	if (writable)
 		prot |= KVM_PGTABLE_PROT_W;
 
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 4f2f1e3145de..e09dbc00b0a2 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
 		val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
 		break;
 	case SYS_ID_AA64PFR1_EL1:
-		val &= ~FEATURE(ID_AA64PFR1_MTE);
+		if (!kvm_has_mte(vcpu->kvm))
+			val &= ~FEATURE(ID_AA64PFR1_MTE);
 		break;
 	case SYS_ID_AA64ISAR1_EL1:
 		if (!vcpu_has_ptrauth(vcpu))
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 8b281f722e5b..05618a4abf7e 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_DIRTY_LOG_RING 192
 #define KVM_CAP_X86_BUS_LOCK_EXIT 193
 #define KVM_CAP_PPC_DAWR1 194
+#define KVM_CAP_ARM_MTE 195
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.20.1

Re: [PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature

[Marc Zyngier]

On Mon, 01 Mar 2021 14:23:11 +0000,
Steven Price <steven.price@arm.com> wrote:
> 
> Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
> for a VM. This will expose the feature to the guest and automatically
> tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
> storage) to ensure that the guest cannot see stale tags, and so that
> the tags are correctly saved/restored across swap.
> 
> Actually exposing the new capability to user space happens in a later
> patch.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/asm/kvm_emulate.h |  3 +++
>  arch/arm64/include/asm/kvm_host.h    |  3 +++
>  arch/arm64/kvm/hyp/exception.c       |  3 ++-
>  arch/arm64/kvm/mmu.c                 | 16 ++++++++++++++++
>  arch/arm64/kvm/sys_regs.c            |  3 ++-
>  include/uapi/linux/kvm.h             |  1 +
>  6 files changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index f612c090f2e4..6bf776c2399c 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>  	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
>  	    vcpu_el1_is_32bit(vcpu))
>  		vcpu->arch.hcr_el2 |= HCR_TID2;
> +
> +	if (kvm_has_mte(vcpu->kvm))
> +		vcpu->arch.hcr_el2 |= HCR_ATA;
>  }
>  
>  static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 3d10e6527f7d..1170ee137096 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -132,6 +132,8 @@ struct kvm_arch {
>  
>  	u8 pfr0_csv2;
>  	u8 pfr0_csv3;
> +	/* Memory Tagging Extension enabled for the guest */
> +	bool mte_enabled;
>  };
>  
>  struct kvm_vcpu_fault_info {
> @@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
>  #define kvm_arm_vcpu_sve_finalized(vcpu) \
>  	((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
>  
> +#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
>  #define kvm_vcpu_has_pmu(vcpu)					\
>  	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
>  
> diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
> index 73629094f903..56426565600c 100644
> --- a/arch/arm64/kvm/hyp/exception.c
> +++ b/arch/arm64/kvm/hyp/exception.c
> @@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
>  	new |= (old & PSR_C_BIT);
>  	new |= (old & PSR_V_BIT);
>  
> -	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
> +	if (kvm_has_mte(vcpu->kvm))
> +		new |= PSR_TCO_BIT;
>  
>  	new |= (old & PSR_DIT_BIT);
>  
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 77cb2d28f2a4..fdb6ab604fd0 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	if (vma_pagesize == PAGE_SIZE && !force_pte)
>  		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
>  							   &pfn, &fault_ipa);
> +
> +	if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
> +		/*
> +		 * VM will be able to see the page's tags, so we must ensure
> +		 * they have been initialised. if PG_mte_tagged is set, tags
> +		 * have already been initialised.
> +		 */
> +		struct page *page = pfn_to_page(pfn);
> +		unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
> +
> +		for (i = 0; i < nr_pages; i++, page++) {
> +			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
> +				mte_clear_page_tags(page_address(page));
> +		}
> +	}

Is there any reason to do this dance for anything but a translation
fault?

> +
>  	if (writable)
>  		prot |= KVM_PGTABLE_PROT_W;
>  
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 4f2f1e3145de..e09dbc00b0a2 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
>  		val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
>  		break;
>  	case SYS_ID_AA64PFR1_EL1:
> -		val &= ~FEATURE(ID_AA64PFR1_MTE);
> +		if (!kvm_has_mte(vcpu->kvm))
> +			val &= ~FEATURE(ID_AA64PFR1_MTE);

Are we happy to expose *any* of the MTE flavours? Or should we
restrict it in any way?

>  		break;
>  	case SYS_ID_AA64ISAR1_EL1:
>  		if (!vcpu_has_ptrauth(vcpu))
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8b281f722e5b..05618a4abf7e 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
>  #define KVM_CAP_DIRTY_LOG_RING 192
>  #define KVM_CAP_X86_BUS_LOCK_EXIT 193
>  #define KVM_CAP_PPC_DAWR1 194
> +#define KVM_CAP_ARM_MTE 195
>  
>  #ifdef KVM_CAP_IRQ_ROUTING
>  
> -- 
> 2.20.1
> 
> 

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

Re: [PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature

[Marc Zyngier]

On Mon, 01 Mar 2021 14:23:11 +0000,
Steven Price <steven.price@arm.com> wrote:
> 
> Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
> for a VM. This will expose the feature to the guest and automatically
> tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
> storage) to ensure that the guest cannot see stale tags, and so that
> the tags are correctly saved/restored across swap.
> 
> Actually exposing the new capability to user space happens in a later
> patch.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/asm/kvm_emulate.h |  3 +++
>  arch/arm64/include/asm/kvm_host.h    |  3 +++
>  arch/arm64/kvm/hyp/exception.c       |  3 ++-
>  arch/arm64/kvm/mmu.c                 | 16 ++++++++++++++++
>  arch/arm64/kvm/sys_regs.c            |  3 ++-
>  include/uapi/linux/kvm.h             |  1 +
>  6 files changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index f612c090f2e4..6bf776c2399c 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>  	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
>  	    vcpu_el1_is_32bit(vcpu))
>  		vcpu->arch.hcr_el2 |= HCR_TID2;
> +
> +	if (kvm_has_mte(vcpu->kvm))
> +		vcpu->arch.hcr_el2 |= HCR_ATA;
>  }
>  
>  static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 3d10e6527f7d..1170ee137096 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -132,6 +132,8 @@ struct kvm_arch {
>  
>  	u8 pfr0_csv2;
>  	u8 pfr0_csv3;
> +	/* Memory Tagging Extension enabled for the guest */
> +	bool mte_enabled;
>  };
>  
>  struct kvm_vcpu_fault_info {
> @@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
>  #define kvm_arm_vcpu_sve_finalized(vcpu) \
>  	((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
>  
> +#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
>  #define kvm_vcpu_has_pmu(vcpu)					\
>  	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
>  
> diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
> index 73629094f903..56426565600c 100644
> --- a/arch/arm64/kvm/hyp/exception.c
> +++ b/arch/arm64/kvm/hyp/exception.c
> @@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
>  	new |= (old & PSR_C_BIT);
>  	new |= (old & PSR_V_BIT);
>  
> -	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
> +	if (kvm_has_mte(vcpu->kvm))
> +		new |= PSR_TCO_BIT;
>  
>  	new |= (old & PSR_DIT_BIT);
>  
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 77cb2d28f2a4..fdb6ab604fd0 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	if (vma_pagesize == PAGE_SIZE && !force_pte)
>  		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
>  							   &pfn, &fault_ipa);
> +
> +	if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
> +		/*
> +		 * VM will be able to see the page's tags, so we must ensure
> +		 * they have been initialised. if PG_mte_tagged is set, tags
> +		 * have already been initialised.
> +		 */
> +		struct page *page = pfn_to_page(pfn);
> +		unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
> +
> +		for (i = 0; i < nr_pages; i++, page++) {
> +			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
> +				mte_clear_page_tags(page_address(page));
> +		}
> +	}

Is there any reason to do this dance for anything but a translation
fault?

> +
>  	if (writable)
>  		prot |= KVM_PGTABLE_PROT_W;
>  
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 4f2f1e3145de..e09dbc00b0a2 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
>  		val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
>  		break;
>  	case SYS_ID_AA64PFR1_EL1:
> -		val &= ~FEATURE(ID_AA64PFR1_MTE);
> +		if (!kvm_has_mte(vcpu->kvm))
> +			val &= ~FEATURE(ID_AA64PFR1_MTE);

Are we happy to expose *any* of the MTE flavours? Or should we
restrict it in any way?

>  		break;
>  	case SYS_ID_AA64ISAR1_EL1:
>  		if (!vcpu_has_ptrauth(vcpu))
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8b281f722e5b..05618a4abf7e 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
>  #define KVM_CAP_DIRTY_LOG_RING 192
>  #define KVM_CAP_X86_BUS_LOCK_EXIT 193
>  #define KVM_CAP_PPC_DAWR1 194
> +#define KVM_CAP_ARM_MTE 195
>  
>  #ifdef KVM_CAP_IRQ_ROUTING
>  
> -- 
> 2.20.1
> 
> 

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature

[Marc Zyngier]

On Mon, 01 Mar 2021 14:23:11 +0000,
Steven Price <steven.price@arm.com> wrote:
> 
> Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
> for a VM. This will expose the feature to the guest and automatically
> tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
> storage) to ensure that the guest cannot see stale tags, and so that
> the tags are correctly saved/restored across swap.
> 
> Actually exposing the new capability to user space happens in a later
> patch.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/asm/kvm_emulate.h |  3 +++
>  arch/arm64/include/asm/kvm_host.h    |  3 +++
>  arch/arm64/kvm/hyp/exception.c       |  3 ++-
>  arch/arm64/kvm/mmu.c                 | 16 ++++++++++++++++
>  arch/arm64/kvm/sys_regs.c            |  3 ++-
>  include/uapi/linux/kvm.h             |  1 +
>  6 files changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index f612c090f2e4..6bf776c2399c 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>  	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
>  	    vcpu_el1_is_32bit(vcpu))
>  		vcpu->arch.hcr_el2 |= HCR_TID2;
> +
> +	if (kvm_has_mte(vcpu->kvm))
> +		vcpu->arch.hcr_el2 |= HCR_ATA;
>  }
>  
>  static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 3d10e6527f7d..1170ee137096 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -132,6 +132,8 @@ struct kvm_arch {
>  
>  	u8 pfr0_csv2;
>  	u8 pfr0_csv3;
> +	/* Memory Tagging Extension enabled for the guest */
> +	bool mte_enabled;
>  };
>  
>  struct kvm_vcpu_fault_info {
> @@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
>  #define kvm_arm_vcpu_sve_finalized(vcpu) \
>  	((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
>  
> +#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
>  #define kvm_vcpu_has_pmu(vcpu)					\
>  	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
>  
> diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
> index 73629094f903..56426565600c 100644
> --- a/arch/arm64/kvm/hyp/exception.c
> +++ b/arch/arm64/kvm/hyp/exception.c
> @@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
>  	new |= (old & PSR_C_BIT);
>  	new |= (old & PSR_V_BIT);
>  
> -	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
> +	if (kvm_has_mte(vcpu->kvm))
> +		new |= PSR_TCO_BIT;
>  
>  	new |= (old & PSR_DIT_BIT);
>  
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 77cb2d28f2a4..fdb6ab604fd0 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	if (vma_pagesize == PAGE_SIZE && !force_pte)
>  		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
>  							   &pfn, &fault_ipa);
> +
> +	if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
> +		/*
> +		 * VM will be able to see the page's tags, so we must ensure
> +		 * they have been initialised. if PG_mte_tagged is set, tags
> +		 * have already been initialised.
> +		 */
> +		struct page *page = pfn_to_page(pfn);
> +		unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
> +
> +		for (i = 0; i < nr_pages; i++, page++) {
> +			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
> +				mte_clear_page_tags(page_address(page));
> +		}
> +	}

Is there any reason to do this dance for anything but a translation
fault?

> +
>  	if (writable)
>  		prot |= KVM_PGTABLE_PROT_W;
>  
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 4f2f1e3145de..e09dbc00b0a2 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
>  		val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
>  		break;
>  	case SYS_ID_AA64PFR1_EL1:
> -		val &= ~FEATURE(ID_AA64PFR1_MTE);
> +		if (!kvm_has_mte(vcpu->kvm))
> +			val &= ~FEATURE(ID_AA64PFR1_MTE);

Are we happy to expose *any* of the MTE flavours? Or should we
restrict it in any way?

>  		break;
>  	case SYS_ID_AA64ISAR1_EL1:
>  		if (!vcpu_has_ptrauth(vcpu))
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8b281f722e5b..05618a4abf7e 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
>  #define KVM_CAP_DIRTY_LOG_RING 192
>  #define KVM_CAP_X86_BUS_LOCK_EXIT 193
>  #define KVM_CAP_PPC_DAWR1 194
> +#define KVM_CAP_ARM_MTE 195
>  
>  #ifdef KVM_CAP_IRQ_ROUTING
>  
> -- 
> 2.20.1
> 
> 

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

Re: [PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature

[Marc Zyngier]

On Mon, 01 Mar 2021 14:23:11 +0000,
Steven Price <steven.price@arm.com> wrote:
> 
> Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
> for a VM. This will expose the feature to the guest and automatically
> tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
> storage) to ensure that the guest cannot see stale tags, and so that
> the tags are correctly saved/restored across swap.
> 
> Actually exposing the new capability to user space happens in a later
> patch.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/asm/kvm_emulate.h |  3 +++
>  arch/arm64/include/asm/kvm_host.h    |  3 +++
>  arch/arm64/kvm/hyp/exception.c       |  3 ++-
>  arch/arm64/kvm/mmu.c                 | 16 ++++++++++++++++
>  arch/arm64/kvm/sys_regs.c            |  3 ++-
>  include/uapi/linux/kvm.h             |  1 +
>  6 files changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index f612c090f2e4..6bf776c2399c 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>  	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
>  	    vcpu_el1_is_32bit(vcpu))
>  		vcpu->arch.hcr_el2 |= HCR_TID2;
> +
> +	if (kvm_has_mte(vcpu->kvm))
> +		vcpu->arch.hcr_el2 |= HCR_ATA;
>  }
>  
>  static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 3d10e6527f7d..1170ee137096 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -132,6 +132,8 @@ struct kvm_arch {
>  
>  	u8 pfr0_csv2;
>  	u8 pfr0_csv3;
> +	/* Memory Tagging Extension enabled for the guest */
> +	bool mte_enabled;
>  };
>  
>  struct kvm_vcpu_fault_info {
> @@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
>  #define kvm_arm_vcpu_sve_finalized(vcpu) \
>  	((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
>  
> +#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
>  #define kvm_vcpu_has_pmu(vcpu)					\
>  	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
>  
> diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
> index 73629094f903..56426565600c 100644
> --- a/arch/arm64/kvm/hyp/exception.c
> +++ b/arch/arm64/kvm/hyp/exception.c
> @@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
>  	new |= (old & PSR_C_BIT);
>  	new |= (old & PSR_V_BIT);
>  
> -	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
> +	if (kvm_has_mte(vcpu->kvm))
> +		new |= PSR_TCO_BIT;
>  
>  	new |= (old & PSR_DIT_BIT);
>  
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 77cb2d28f2a4..fdb6ab604fd0 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	if (vma_pagesize == PAGE_SIZE && !force_pte)
>  		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
>  							   &pfn, &fault_ipa);
> +
> +	if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
> +		/*
> +		 * VM will be able to see the page's tags, so we must ensure
> +		 * they have been initialised. if PG_mte_tagged is set, tags
> +		 * have already been initialised.
> +		 */
> +		struct page *page = pfn_to_page(pfn);
> +		unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
> +
> +		for (i = 0; i < nr_pages; i++, page++) {
> +			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
> +				mte_clear_page_tags(page_address(page));
> +		}
> +	}

Is there any reason to do this dance for anything but a translation
fault?

> +
>  	if (writable)
>  		prot |= KVM_PGTABLE_PROT_W;
>  
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 4f2f1e3145de..e09dbc00b0a2 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
>  		val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
>  		break;
>  	case SYS_ID_AA64PFR1_EL1:
> -		val &= ~FEATURE(ID_AA64PFR1_MTE);
> +		if (!kvm_has_mte(vcpu->kvm))
> +			val &= ~FEATURE(ID_AA64PFR1_MTE);

Are we happy to expose *any* of the MTE flavours? Or should we
restrict it in any way?

>  		break;
>  	case SYS_ID_AA64ISAR1_EL1:
>  		if (!vcpu_has_ptrauth(vcpu))
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8b281f722e5b..05618a4abf7e 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
>  #define KVM_CAP_DIRTY_LOG_RING 192
>  #define KVM_CAP_X86_BUS_LOCK_EXIT 193
>  #define KVM_CAP_PPC_DAWR1 194
> +#define KVM_CAP_ARM_MTE 195
>  
>  #ifdef KVM_CAP_IRQ_ROUTING
>  
> -- 
> 2.20.1
> 
> 

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

Re: [PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature

[Steven Price]

On 09/03/2021 17:06, Marc Zyngier wrote:
> On Mon, 01 Mar 2021 14:23:11 +0000,
> Steven Price <steven.price@arm.com> wrote:
>>
>> Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
>> for a VM. This will expose the feature to the guest and automatically
>> tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
>> storage) to ensure that the guest cannot see stale tags, and so that
>> the tags are correctly saved/restored across swap.
>>
>> Actually exposing the new capability to user space happens in a later
>> patch.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/asm/kvm_emulate.h |  3 +++
>>   arch/arm64/include/asm/kvm_host.h    |  3 +++
>>   arch/arm64/kvm/hyp/exception.c       |  3 ++-
>>   arch/arm64/kvm/mmu.c                 | 16 ++++++++++++++++
>>   arch/arm64/kvm/sys_regs.c            |  3 ++-
>>   include/uapi/linux/kvm.h             |  1 +
>>   6 files changed, 27 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>> index f612c090f2e4..6bf776c2399c 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>>   	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
>>   	    vcpu_el1_is_32bit(vcpu))
>>   		vcpu->arch.hcr_el2 |= HCR_TID2;
>> +
>> +	if (kvm_has_mte(vcpu->kvm))
>> +		vcpu->arch.hcr_el2 |= HCR_ATA;
>>   }
>>   
>>   static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 3d10e6527f7d..1170ee137096 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -132,6 +132,8 @@ struct kvm_arch {
>>   
>>   	u8 pfr0_csv2;
>>   	u8 pfr0_csv3;
>> +	/* Memory Tagging Extension enabled for the guest */
>> +	bool mte_enabled;
>>   };
>>   
>>   struct kvm_vcpu_fault_info {
>> @@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
>>   #define kvm_arm_vcpu_sve_finalized(vcpu) \
>>   	((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
>>   
>> +#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
>>   #define kvm_vcpu_has_pmu(vcpu)					\
>>   	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
>>   
>> diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
>> index 73629094f903..56426565600c 100644
>> --- a/arch/arm64/kvm/hyp/exception.c
>> +++ b/arch/arm64/kvm/hyp/exception.c
>> @@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
>>   	new |= (old & PSR_C_BIT);
>>   	new |= (old & PSR_V_BIT);
>>   
>> -	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
>> +	if (kvm_has_mte(vcpu->kvm))
>> +		new |= PSR_TCO_BIT;
>>   
>>   	new |= (old & PSR_DIT_BIT);
>>   
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index 77cb2d28f2a4..fdb6ab604fd0 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>   	if (vma_pagesize == PAGE_SIZE && !force_pte)
>>   		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
>>   							   &pfn, &fault_ipa);
>> +
>> +	if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
>> +		/*
>> +		 * VM will be able to see the page's tags, so we must ensure
>> +		 * they have been initialised. if PG_mte_tagged is set, tags
>> +		 * have already been initialised.
>> +		 */
>> +		struct page *page = pfn_to_page(pfn);
>> +		unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
>> +
>> +		for (i = 0; i < nr_pages; i++, page++) {
>> +			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
>> +				mte_clear_page_tags(page_address(page));
>> +		}
>> +	}
> 
> Is there any reason to do this dance for anything but a translation
> fault?

Good point I guess this should have a (fault_status != FSC_PERM) in the 
test to match the other paths.

>> +
>>   	if (writable)
>>   		prot |= KVM_PGTABLE_PROT_W;
>>   
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index 4f2f1e3145de..e09dbc00b0a2 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
>>   		val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
>>   		break;
>>   	case SYS_ID_AA64PFR1_EL1:
>> -		val &= ~FEATURE(ID_AA64PFR1_MTE);
>> +		if (!kvm_has_mte(vcpu->kvm))
>> +			val &= ~FEATURE(ID_AA64PFR1_MTE);
> 
> Are we happy to expose *any* of the MTE flavours? Or should we
> restrict it in any way?

Another good point - it would make sense to restrict this in case 
another MTE flavour is invented.

Thanks,

Steve

>>   		break;
>>   	case SYS_ID_AA64ISAR1_EL1:
>>   		if (!vcpu_has_ptrauth(vcpu))
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 8b281f722e5b..05618a4abf7e 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
>>   #define KVM_CAP_DIRTY_LOG_RING 192
>>   #define KVM_CAP_X86_BUS_LOCK_EXIT 193
>>   #define KVM_CAP_PPC_DAWR1 194
>> +#define KVM_CAP_ARM_MTE 195
>>   
>>   #ifdef KVM_CAP_IRQ_ROUTING
>>   
>> -- 
>> 2.20.1
>>
>>
> 
> Thanks,
> 
> 	M.
> 

Re: [PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature

[Steven Price]

On 09/03/2021 17:06, Marc Zyngier wrote:
> On Mon, 01 Mar 2021 14:23:11 +0000,
> Steven Price <steven.price@arm.com> wrote:
>>
>> Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
>> for a VM. This will expose the feature to the guest and automatically
>> tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
>> storage) to ensure that the guest cannot see stale tags, and so that
>> the tags are correctly saved/restored across swap.
>>
>> Actually exposing the new capability to user space happens in a later
>> patch.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/asm/kvm_emulate.h |  3 +++
>>   arch/arm64/include/asm/kvm_host.h    |  3 +++
>>   arch/arm64/kvm/hyp/exception.c       |  3 ++-
>>   arch/arm64/kvm/mmu.c                 | 16 ++++++++++++++++
>>   arch/arm64/kvm/sys_regs.c            |  3 ++-
>>   include/uapi/linux/kvm.h             |  1 +
>>   6 files changed, 27 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>> index f612c090f2e4..6bf776c2399c 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>>   	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
>>   	    vcpu_el1_is_32bit(vcpu))
>>   		vcpu->arch.hcr_el2 |= HCR_TID2;
>> +
>> +	if (kvm_has_mte(vcpu->kvm))
>> +		vcpu->arch.hcr_el2 |= HCR_ATA;
>>   }
>>   
>>   static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 3d10e6527f7d..1170ee137096 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -132,6 +132,8 @@ struct kvm_arch {
>>   
>>   	u8 pfr0_csv2;
>>   	u8 pfr0_csv3;
>> +	/* Memory Tagging Extension enabled for the guest */
>> +	bool mte_enabled;
>>   };
>>   
>>   struct kvm_vcpu_fault_info {
>> @@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
>>   #define kvm_arm_vcpu_sve_finalized(vcpu) \
>>   	((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
>>   
>> +#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
>>   #define kvm_vcpu_has_pmu(vcpu)					\
>>   	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
>>   
>> diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
>> index 73629094f903..56426565600c 100644
>> --- a/arch/arm64/kvm/hyp/exception.c
>> +++ b/arch/arm64/kvm/hyp/exception.c
>> @@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
>>   	new |= (old & PSR_C_BIT);
>>   	new |= (old & PSR_V_BIT);
>>   
>> -	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
>> +	if (kvm_has_mte(vcpu->kvm))
>> +		new |= PSR_TCO_BIT;
>>   
>>   	new |= (old & PSR_DIT_BIT);
>>   
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index 77cb2d28f2a4..fdb6ab604fd0 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>   	if (vma_pagesize == PAGE_SIZE && !force_pte)
>>   		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
>>   							   &pfn, &fault_ipa);
>> +
>> +	if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
>> +		/*
>> +		 * VM will be able to see the page's tags, so we must ensure
>> +		 * they have been initialised. if PG_mte_tagged is set, tags
>> +		 * have already been initialised.
>> +		 */
>> +		struct page *page = pfn_to_page(pfn);
>> +		unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
>> +
>> +		for (i = 0; i < nr_pages; i++, page++) {
>> +			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
>> +				mte_clear_page_tags(page_address(page));
>> +		}
>> +	}
> 
> Is there any reason to do this dance for anything but a translation
> fault?

Good point I guess this should have a (fault_status != FSC_PERM) in the 
test to match the other paths.

>> +
>>   	if (writable)
>>   		prot |= KVM_PGTABLE_PROT_W;
>>   
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index 4f2f1e3145de..e09dbc00b0a2 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
>>   		val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
>>   		break;
>>   	case SYS_ID_AA64PFR1_EL1:
>> -		val &= ~FEATURE(ID_AA64PFR1_MTE);
>> +		if (!kvm_has_mte(vcpu->kvm))
>> +			val &= ~FEATURE(ID_AA64PFR1_MTE);
> 
> Are we happy to expose *any* of the MTE flavours? Or should we
> restrict it in any way?

Another good point - it would make sense to restrict this in case 
another MTE flavour is invented.

Thanks,

Steve

>>   		break;
>>   	case SYS_ID_AA64ISAR1_EL1:
>>   		if (!vcpu_has_ptrauth(vcpu))
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 8b281f722e5b..05618a4abf7e 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
>>   #define KVM_CAP_DIRTY_LOG_RING 192
>>   #define KVM_CAP_X86_BUS_LOCK_EXIT 193
>>   #define KVM_CAP_PPC_DAWR1 194
>> +#define KVM_CAP_ARM_MTE 195
>>   
>>   #ifdef KVM_CAP_IRQ_ROUTING
>>   
>> -- 
>> 2.20.1
>>
>>
> 
> Thanks,
> 
> 	M.
> 


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature

[Steven Price]

On 09/03/2021 17:06, Marc Zyngier wrote:
> On Mon, 01 Mar 2021 14:23:11 +0000,
> Steven Price <steven.price@arm.com> wrote:
>>
>> Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
>> for a VM. This will expose the feature to the guest and automatically
>> tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
>> storage) to ensure that the guest cannot see stale tags, and so that
>> the tags are correctly saved/restored across swap.
>>
>> Actually exposing the new capability to user space happens in a later
>> patch.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/asm/kvm_emulate.h |  3 +++
>>   arch/arm64/include/asm/kvm_host.h    |  3 +++
>>   arch/arm64/kvm/hyp/exception.c       |  3 ++-
>>   arch/arm64/kvm/mmu.c                 | 16 ++++++++++++++++
>>   arch/arm64/kvm/sys_regs.c            |  3 ++-
>>   include/uapi/linux/kvm.h             |  1 +
>>   6 files changed, 27 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>> index f612c090f2e4..6bf776c2399c 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>>   	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
>>   	    vcpu_el1_is_32bit(vcpu))
>>   		vcpu->arch.hcr_el2 |= HCR_TID2;
>> +
>> +	if (kvm_has_mte(vcpu->kvm))
>> +		vcpu->arch.hcr_el2 |= HCR_ATA;
>>   }
>>   
>>   static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 3d10e6527f7d..1170ee137096 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -132,6 +132,8 @@ struct kvm_arch {
>>   
>>   	u8 pfr0_csv2;
>>   	u8 pfr0_csv3;
>> +	/* Memory Tagging Extension enabled for the guest */
>> +	bool mte_enabled;
>>   };
>>   
>>   struct kvm_vcpu_fault_info {
>> @@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
>>   #define kvm_arm_vcpu_sve_finalized(vcpu) \
>>   	((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
>>   
>> +#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
>>   #define kvm_vcpu_has_pmu(vcpu)					\
>>   	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
>>   
>> diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
>> index 73629094f903..56426565600c 100644
>> --- a/arch/arm64/kvm/hyp/exception.c
>> +++ b/arch/arm64/kvm/hyp/exception.c
>> @@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
>>   	new |= (old & PSR_C_BIT);
>>   	new |= (old & PSR_V_BIT);
>>   
>> -	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
>> +	if (kvm_has_mte(vcpu->kvm))
>> +		new |= PSR_TCO_BIT;
>>   
>>   	new |= (old & PSR_DIT_BIT);
>>   
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index 77cb2d28f2a4..fdb6ab604fd0 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>   	if (vma_pagesize == PAGE_SIZE && !force_pte)
>>   		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
>>   							   &pfn, &fault_ipa);
>> +
>> +	if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
>> +		/*
>> +		 * VM will be able to see the page's tags, so we must ensure
>> +		 * they have been initialised. if PG_mte_tagged is set, tags
>> +		 * have already been initialised.
>> +		 */
>> +		struct page *page = pfn_to_page(pfn);
>> +		unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
>> +
>> +		for (i = 0; i < nr_pages; i++, page++) {
>> +			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
>> +				mte_clear_page_tags(page_address(page));
>> +		}
>> +	}
> 
> Is there any reason to do this dance for anything but a translation
> fault?

Good point I guess this should have a (fault_status != FSC_PERM) in the 
test to match the other paths.

>> +
>>   	if (writable)
>>   		prot |= KVM_PGTABLE_PROT_W;
>>   
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index 4f2f1e3145de..e09dbc00b0a2 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
>>   		val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
>>   		break;
>>   	case SYS_ID_AA64PFR1_EL1:
>> -		val &= ~FEATURE(ID_AA64PFR1_MTE);
>> +		if (!kvm_has_mte(vcpu->kvm))
>> +			val &= ~FEATURE(ID_AA64PFR1_MTE);
> 
> Are we happy to expose *any* of the MTE flavours? Or should we
> restrict it in any way?

Another good point - it would make sense to restrict this in case 
another MTE flavour is invented.

Thanks,

Steve

>>   		break;
>>   	case SYS_ID_AA64ISAR1_EL1:
>>   		if (!vcpu_has_ptrauth(vcpu))
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 8b281f722e5b..05618a4abf7e 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
>>   #define KVM_CAP_DIRTY_LOG_RING 192
>>   #define KVM_CAP_X86_BUS_LOCK_EXIT 193
>>   #define KVM_CAP_PPC_DAWR1 194
>> +#define KVM_CAP_ARM_MTE 195
>>   
>>   #ifdef KVM_CAP_IRQ_ROUTING
>>   
>> -- 
>> 2.20.1
>>
>>
> 
> Thanks,
> 
> 	M.
> 

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

Re: [PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature

[Steven Price]

On 09/03/2021 17:06, Marc Zyngier wrote:
> On Mon, 01 Mar 2021 14:23:11 +0000,
> Steven Price <steven.price@arm.com> wrote:
>>
>> Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
>> for a VM. This will expose the feature to the guest and automatically
>> tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
>> storage) to ensure that the guest cannot see stale tags, and so that
>> the tags are correctly saved/restored across swap.
>>
>> Actually exposing the new capability to user space happens in a later
>> patch.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/asm/kvm_emulate.h |  3 +++
>>   arch/arm64/include/asm/kvm_host.h    |  3 +++
>>   arch/arm64/kvm/hyp/exception.c       |  3 ++-
>>   arch/arm64/kvm/mmu.c                 | 16 ++++++++++++++++
>>   arch/arm64/kvm/sys_regs.c            |  3 ++-
>>   include/uapi/linux/kvm.h             |  1 +
>>   6 files changed, 27 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>> index f612c090f2e4..6bf776c2399c 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>>   	if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
>>   	    vcpu_el1_is_32bit(vcpu))
>>   		vcpu->arch.hcr_el2 |= HCR_TID2;
>> +
>> +	if (kvm_has_mte(vcpu->kvm))
>> +		vcpu->arch.hcr_el2 |= HCR_ATA;
>>   }
>>   
>>   static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 3d10e6527f7d..1170ee137096 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -132,6 +132,8 @@ struct kvm_arch {
>>   
>>   	u8 pfr0_csv2;
>>   	u8 pfr0_csv3;
>> +	/* Memory Tagging Extension enabled for the guest */
>> +	bool mte_enabled;
>>   };
>>   
>>   struct kvm_vcpu_fault_info {
>> @@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
>>   #define kvm_arm_vcpu_sve_finalized(vcpu) \
>>   	((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
>>   
>> +#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
>>   #define kvm_vcpu_has_pmu(vcpu)					\
>>   	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
>>   
>> diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
>> index 73629094f903..56426565600c 100644
>> --- a/arch/arm64/kvm/hyp/exception.c
>> +++ b/arch/arm64/kvm/hyp/exception.c
>> @@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
>>   	new |= (old & PSR_C_BIT);
>>   	new |= (old & PSR_V_BIT);
>>   
>> -	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
>> +	if (kvm_has_mte(vcpu->kvm))
>> +		new |= PSR_TCO_BIT;
>>   
>>   	new |= (old & PSR_DIT_BIT);
>>   
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index 77cb2d28f2a4..fdb6ab604fd0 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>   	if (vma_pagesize == PAGE_SIZE && !force_pte)
>>   		vma_pagesize = transparent_hugepage_adjust(memslot, hva,
>>   							   &pfn, &fault_ipa);
>> +
>> +	if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
>> +		/*
>> +		 * VM will be able to see the page's tags, so we must ensure
>> +		 * they have been initialised. if PG_mte_tagged is set, tags
>> +		 * have already been initialised.
>> +		 */
>> +		struct page *page = pfn_to_page(pfn);
>> +		unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
>> +
>> +		for (i = 0; i < nr_pages; i++, page++) {
>> +			if (!test_and_set_bit(PG_mte_tagged, &page->flags))
>> +				mte_clear_page_tags(page_address(page));
>> +		}
>> +	}
> 
> Is there any reason to do this dance for anything but a translation
> fault?

Good point I guess this should have a (fault_status != FSC_PERM) in the 
test to match the other paths.

>> +
>>   	if (writable)
>>   		prot |= KVM_PGTABLE_PROT_W;
>>   
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index 4f2f1e3145de..e09dbc00b0a2 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
>>   		val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
>>   		break;
>>   	case SYS_ID_AA64PFR1_EL1:
>> -		val &= ~FEATURE(ID_AA64PFR1_MTE);
>> +		if (!kvm_has_mte(vcpu->kvm))
>> +			val &= ~FEATURE(ID_AA64PFR1_MTE);
> 
> Are we happy to expose *any* of the MTE flavours? Or should we
> restrict it in any way?

Another good point - it would make sense to restrict this in case 
another MTE flavour is invented.

Thanks,

Steve

>>   		break;
>>   	case SYS_ID_AA64ISAR1_EL1:
>>   		if (!vcpu_has_ptrauth(vcpu))
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 8b281f722e5b..05618a4abf7e 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
>>   #define KVM_CAP_DIRTY_LOG_RING 192
>>   #define KVM_CAP_X86_BUS_LOCK_EXIT 193
>>   #define KVM_CAP_PPC_DAWR1 194
>> +#define KVM_CAP_ARM_MTE 195
>>   
>>   #ifdef KVM_CAP_IRQ_ROUTING
>>   
>> -- 
>> 2.20.1
>>
>>
> 
> Thanks,
> 
> 	M.
> 

[PATCH v9 3/6] arm64: kvm: Save/restore MTE registers

[Steven Price]

Define the new system registers that MTE introduces and context switch
them. The MTE feature is still hidden from the ID register as it isn't
supported in a VM yet.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/kvm_host.h          |  6 ++
 arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
 arch/arm64/include/asm/sysreg.h            |  3 +-
 arch/arm64/kernel/asm-offsets.c            |  3 +
 arch/arm64/kvm/hyp/entry.S                 |  7 +++
 arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
 arch/arm64/kvm/sys_regs.c                  | 22 ++++++--
 7 files changed, 123 insertions(+), 5 deletions(-)
 create mode 100644 arch/arm64/include/asm/kvm_mte.h

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 1170ee137096..d00cc3590f6e 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -208,6 +208,12 @@ enum vcpu_sysreg {
 	CNTP_CVAL_EL0,
 	CNTP_CTL_EL0,
 
+	/* Memory Tagging Extension registers */
+	RGSR_EL1,	/* Random Allocation Tag Seed Register */
+	GCR_EL1,	/* Tag Control Register */
+	TFSR_EL1,	/* Tag Fault Status Register (EL1) */
+	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
+
 	/* 32bit specific registers. Keep them at the end of the range */
 	DACR32_EL2,	/* Domain Access Control Register */
 	IFSR32_EL2,	/* Instruction Fault Status Register */
diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
new file mode 100644
index 000000000000..6541c7d6ce06
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_mte.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 ARM Ltd.
+ */
+#ifndef __ASM_KVM_MTE_H
+#define __ASM_KVM_MTE_H
+
+#ifdef __ASSEMBLY__
+
+#include <asm/sysreg.h>
+
+#ifdef CONFIG_ARM64_MTE
+
+.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
+alternative_if_not ARM64_MTE
+	b	.L__skip_switch\@
+alternative_else_nop_endif
+	mrs	\reg1, hcr_el2
+	and	\reg1, \reg1, #(HCR_ATA)
+	cbz	\reg1, .L__skip_switch\@
+
+	mrs_s	\reg1, SYS_RGSR_EL1
+	str	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
+	mrs_s	\reg1, SYS_GCR_EL1
+	str	\reg1, [\h_ctxt, #CPU_GCR_EL1]
+
+	ldr	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
+	msr_s	SYS_RGSR_EL1, \reg1
+	ldr	\reg1, [\g_ctxt, #CPU_GCR_EL1]
+	msr_s	SYS_GCR_EL1, \reg1
+
+.L__skip_switch\@:
+.endm
+
+.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
+alternative_if_not ARM64_MTE
+	b	.L__skip_switch\@
+alternative_else_nop_endif
+	mrs	\reg1, hcr_el2
+	and	\reg1, \reg1, #(HCR_ATA)
+	cbz	\reg1, .L__skip_switch\@
+
+	mrs_s	\reg1, SYS_RGSR_EL1
+	str	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
+	mrs_s	\reg1, SYS_GCR_EL1
+	str	\reg1, [\g_ctxt, #CPU_GCR_EL1]
+
+	ldr	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
+	msr_s	SYS_RGSR_EL1, \reg1
+	ldr	\reg1, [\h_ctxt, #CPU_GCR_EL1]
+	msr_s	SYS_GCR_EL1, \reg1
+
+.L__skip_switch\@:
+.endm
+
+#else /* CONFIG_ARM64_MTE */
+
+.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
+.endm
+
+.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
+.endm
+
+#endif /* CONFIG_ARM64_MTE */
+#endif /* __ASSEMBLY__ */
+#endif /* __ASM_KVM_MTE_H */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index dfd4edbfe360..5424d195cf96 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -580,7 +580,8 @@
 #define SCTLR_ELx_M	(BIT(0))
 
 #define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
-			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
+			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
+			 SCTLR_ELx_ITFSB)
 
 /* SCTLR_EL2 specific flags. */
 #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index a36e2fc330d4..944e4f1f45d9 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -108,6 +108,9 @@ int main(void)
   DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));
   DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
   DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
+  DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
+  DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
+  DEFINE(CPU_TFSRE0_EL1,	offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_EL1]));
   DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
   DEFINE(CPU_APIBKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
   DEFINE(CPU_APDAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index b0afad7a99c6..c67582c6dd55 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -13,6 +13,7 @@
 #include <asm/kvm_arm.h>
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmu.h>
+#include <asm/kvm_mte.h>
 #include <asm/kvm_ptrauth.h>
 
 	.text
@@ -51,6 +52,9 @@ alternative_else_nop_endif
 
 	add	x29, x0, #VCPU_CONTEXT
 
+	// mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
+	mte_switch_to_guest x29, x1, x2
+
 	// Macro ptrauth_switch_to_guest format:
 	// 	ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
 	// The below macro to restore guest keys is not implemented in C code
@@ -140,6 +144,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
 	// when this feature is enabled for kernel code.
 	ptrauth_switch_to_hyp x1, x2, x3, x4, x5
 
+	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
+	mte_switch_to_hyp x1, x2, x3
+
 	// Restore hyp's sp_el0
 	restore_sp_el0 x2, x3
 
diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
index cce43bfe158f..de7e14c862e6 100644
--- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
+++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
@@ -14,6 +14,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_hyp.h>
+#include <asm/kvm_mmu.h>
 
 static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
 {
@@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
 	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
 }
 
+static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
+{
+	struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
+
+	if (!vcpu)
+		vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
+
+	return kvm_has_mte(kern_hyp_va(vcpu->kvm));
+}
+
 static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 {
 	ctxt_sys_reg(ctxt, CSSELR_EL1)	= read_sysreg(csselr_el1);
@@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
 	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
 
+	if (ctxt_has_mte(ctxt)) {
+		ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
+		ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
+	}
+
 	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);
 	ctxt_sys_reg(ctxt, ELR_EL1)	= read_sysreg_el1(SYS_ELR);
 	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
@@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
 	write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),	par_el1);
 	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),	tpidr_el1);
 
+	if (ctxt_has_mte(ctxt)) {
+		write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
+		write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
+	}
+
 	if (!has_vhe() &&
 	    cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
 	    ctxt->__hyp_running_vcpu) {
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index e09dbc00b0a2..17cb6256f205 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1301,6 +1301,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	return true;
 }
 
+static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
+				   const struct sys_reg_desc *rd)
+{
+	return REG_HIDDEN;
+}
+
+#define MTE_REG(name) {				\
+	SYS_DESC(SYS_##name),			\
+	.access = undef_access,			\
+	.reset = reset_unknown,			\
+	.reg = name,				\
+	.visibility = mte_visibility,		\
+}
+
 /* sys_reg_desc initialiser for known cpufeature ID registers */
 #define ID_SANITISED(name) {			\
 	SYS_DESC(SYS_##name),			\
@@ -1469,8 +1483,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
 	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
 
-	{ SYS_DESC(SYS_RGSR_EL1), undef_access },
-	{ SYS_DESC(SYS_GCR_EL1), undef_access },
+	MTE_REG(RGSR_EL1),
+	MTE_REG(GCR_EL1),
 
 	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
 	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
@@ -1496,8 +1510,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
 	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
 
-	{ SYS_DESC(SYS_TFSR_EL1), undef_access },
-	{ SYS_DESC(SYS_TFSRE0_EL1), undef_access },
+	MTE_REG(TFSR_EL1),
+	MTE_REG(TFSRE0_EL1),
 
 	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
 	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
-- 
2.20.1

[PATCH v9 3/6] arm64: kvm: Save/restore MTE registers

[Steven Price]

Define the new system registers that MTE introduces and context switch
them. The MTE feature is still hidden from the ID register as it isn't
supported in a VM yet.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/kvm_host.h          |  6 ++
 arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
 arch/arm64/include/asm/sysreg.h            |  3 +-
 arch/arm64/kernel/asm-offsets.c            |  3 +
 arch/arm64/kvm/hyp/entry.S                 |  7 +++
 arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
 arch/arm64/kvm/sys_regs.c                  | 22 ++++++--
 7 files changed, 123 insertions(+), 5 deletions(-)
 create mode 100644 arch/arm64/include/asm/kvm_mte.h

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 1170ee137096..d00cc3590f6e 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -208,6 +208,12 @@ enum vcpu_sysreg {
 	CNTP_CVAL_EL0,
 	CNTP_CTL_EL0,
 
+	/* Memory Tagging Extension registers */
+	RGSR_EL1,	/* Random Allocation Tag Seed Register */
+	GCR_EL1,	/* Tag Control Register */
+	TFSR_EL1,	/* Tag Fault Status Register (EL1) */
+	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
+
 	/* 32bit specific registers. Keep them at the end of the range */
 	DACR32_EL2,	/* Domain Access Control Register */
 	IFSR32_EL2,	/* Instruction Fault Status Register */
diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
new file mode 100644
index 000000000000..6541c7d6ce06
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_mte.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 ARM Ltd.
+ */
+#ifndef __ASM_KVM_MTE_H
+#define __ASM_KVM_MTE_H
+
+#ifdef __ASSEMBLY__
+
+#include <asm/sysreg.h>
+
+#ifdef CONFIG_ARM64_MTE
+
+.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
+alternative_if_not ARM64_MTE
+	b	.L__skip_switch\@
+alternative_else_nop_endif
+	mrs	\reg1, hcr_el2
+	and	\reg1, \reg1, #(HCR_ATA)
+	cbz	\reg1, .L__skip_switch\@
+
+	mrs_s	\reg1, SYS_RGSR_EL1
+	str	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
+	mrs_s	\reg1, SYS_GCR_EL1
+	str	\reg1, [\h_ctxt, #CPU_GCR_EL1]
+
+	ldr	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
+	msr_s	SYS_RGSR_EL1, \reg1
+	ldr	\reg1, [\g_ctxt, #CPU_GCR_EL1]
+	msr_s	SYS_GCR_EL1, \reg1
+
+.L__skip_switch\@:
+.endm
+
+.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
+alternative_if_not ARM64_MTE
+	b	.L__skip_switch\@
+alternative_else_nop_endif
+	mrs	\reg1, hcr_el2
+	and	\reg1, \reg1, #(HCR_ATA)
+	cbz	\reg1, .L__skip_switch\@
+
+	mrs_s	\reg1, SYS_RGSR_EL1
+	str	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
+	mrs_s	\reg1, SYS_GCR_EL1
+	str	\reg1, [\g_ctxt, #CPU_GCR_EL1]
+
+	ldr	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
+	msr_s	SYS_RGSR_EL1, \reg1
+	ldr	\reg1, [\h_ctxt, #CPU_GCR_EL1]
+	msr_s	SYS_GCR_EL1, \reg1
+
+.L__skip_switch\@:
+.endm
+
+#else /* CONFIG_ARM64_MTE */
+
+.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
+.endm
+
+.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
+.endm
+
+#endif /* CONFIG_ARM64_MTE */
+#endif /* __ASSEMBLY__ */
+#endif /* __ASM_KVM_MTE_H */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index dfd4edbfe360..5424d195cf96 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -580,7 +580,8 @@
 #define SCTLR_ELx_M	(BIT(0))
 
 #define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
-			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
+			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
+			 SCTLR_ELx_ITFSB)
 
 /* SCTLR_EL2 specific flags. */
 #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index a36e2fc330d4..944e4f1f45d9 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -108,6 +108,9 @@ int main(void)
   DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));
   DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
   DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
+  DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
+  DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
+  DEFINE(CPU_TFSRE0_EL1,	offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_EL1]));
   DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
   DEFINE(CPU_APIBKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
   DEFINE(CPU_APDAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index b0afad7a99c6..c67582c6dd55 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -13,6 +13,7 @@
 #include <asm/kvm_arm.h>
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmu.h>
+#include <asm/kvm_mte.h>
 #include <asm/kvm_ptrauth.h>
 
 	.text
@@ -51,6 +52,9 @@ alternative_else_nop_endif
 
 	add	x29, x0, #VCPU_CONTEXT
 
+	// mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
+	mte_switch_to_guest x29, x1, x2
+
 	// Macro ptrauth_switch_to_guest format:
 	// 	ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
 	// The below macro to restore guest keys is not implemented in C code
@@ -140,6 +144,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
 	// when this feature is enabled for kernel code.
 	ptrauth_switch_to_hyp x1, x2, x3, x4, x5
 
+	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
+	mte_switch_to_hyp x1, x2, x3
+
 	// Restore hyp's sp_el0
 	restore_sp_el0 x2, x3
 
diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
index cce43bfe158f..de7e14c862e6 100644
--- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
+++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
@@ -14,6 +14,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_hyp.h>
+#include <asm/kvm_mmu.h>
 
 static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
 {
@@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
 	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
 }
 
+static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
+{
+	struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
+
+	if (!vcpu)
+		vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
+
+	return kvm_has_mte(kern_hyp_va(vcpu->kvm));
+}
+
 static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 {
 	ctxt_sys_reg(ctxt, CSSELR_EL1)	= read_sysreg(csselr_el1);
@@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
 	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
 
+	if (ctxt_has_mte(ctxt)) {
+		ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
+		ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
+	}
+
 	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);
 	ctxt_sys_reg(ctxt, ELR_EL1)	= read_sysreg_el1(SYS_ELR);
 	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
@@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
 	write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),	par_el1);
 	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),	tpidr_el1);
 
+	if (ctxt_has_mte(ctxt)) {
+		write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
+		write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
+	}
+
 	if (!has_vhe() &&
 	    cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
 	    ctxt->__hyp_running_vcpu) {
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index e09dbc00b0a2..17cb6256f205 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1301,6 +1301,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	return true;
 }
 
+static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
+				   const struct sys_reg_desc *rd)
+{
+	return REG_HIDDEN;
+}
+
+#define MTE_REG(name) {				\
+	SYS_DESC(SYS_##name),			\
+	.access = undef_access,			\
+	.reset = reset_unknown,			\
+	.reg = name,				\
+	.visibility = mte_visibility,		\
+}
+
 /* sys_reg_desc initialiser for known cpufeature ID registers */
 #define ID_SANITISED(name) {			\
 	SYS_DESC(SYS_##name),			\
@@ -1469,8 +1483,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
 	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
 
-	{ SYS_DESC(SYS_RGSR_EL1), undef_access },
-	{ SYS_DESC(SYS_GCR_EL1), undef_access },
+	MTE_REG(RGSR_EL1),
+	MTE_REG(GCR_EL1),
 
 	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
 	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
@@ -1496,8 +1510,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
 	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
 
-	{ SYS_DESC(SYS_TFSR_EL1), undef_access },
-	{ SYS_DESC(SYS_TFSRE0_EL1), undef_access },
+	MTE_REG(TFSR_EL1),
+	MTE_REG(TFSRE0_EL1),
 
 	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
 	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
-- 
2.20.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v9 3/6] arm64: kvm: Save/restore MTE registers

[Steven Price]

Define the new system registers that MTE introduces and context switch
them. The MTE feature is still hidden from the ID register as it isn't
supported in a VM yet.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/kvm_host.h          |  6 ++
 arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
 arch/arm64/include/asm/sysreg.h            |  3 +-
 arch/arm64/kernel/asm-offsets.c            |  3 +
 arch/arm64/kvm/hyp/entry.S                 |  7 +++
 arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
 arch/arm64/kvm/sys_regs.c                  | 22 ++++++--
 7 files changed, 123 insertions(+), 5 deletions(-)
 create mode 100644 arch/arm64/include/asm/kvm_mte.h

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 1170ee137096..d00cc3590f6e 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -208,6 +208,12 @@ enum vcpu_sysreg {
 	CNTP_CVAL_EL0,
 	CNTP_CTL_EL0,
 
+	/* Memory Tagging Extension registers */
+	RGSR_EL1,	/* Random Allocation Tag Seed Register */
+	GCR_EL1,	/* Tag Control Register */
+	TFSR_EL1,	/* Tag Fault Status Register (EL1) */
+	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
+
 	/* 32bit specific registers. Keep them at the end of the range */
 	DACR32_EL2,	/* Domain Access Control Register */
 	IFSR32_EL2,	/* Instruction Fault Status Register */
diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
new file mode 100644
index 000000000000..6541c7d6ce06
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_mte.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 ARM Ltd.
+ */
+#ifndef __ASM_KVM_MTE_H
+#define __ASM_KVM_MTE_H
+
+#ifdef __ASSEMBLY__
+
+#include <asm/sysreg.h>
+
+#ifdef CONFIG_ARM64_MTE
+
+.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
+alternative_if_not ARM64_MTE
+	b	.L__skip_switch\@
+alternative_else_nop_endif
+	mrs	\reg1, hcr_el2
+	and	\reg1, \reg1, #(HCR_ATA)
+	cbz	\reg1, .L__skip_switch\@
+
+	mrs_s	\reg1, SYS_RGSR_EL1
+	str	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
+	mrs_s	\reg1, SYS_GCR_EL1
+	str	\reg1, [\h_ctxt, #CPU_GCR_EL1]
+
+	ldr	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
+	msr_s	SYS_RGSR_EL1, \reg1
+	ldr	\reg1, [\g_ctxt, #CPU_GCR_EL1]
+	msr_s	SYS_GCR_EL1, \reg1
+
+.L__skip_switch\@:
+.endm
+
+.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
+alternative_if_not ARM64_MTE
+	b	.L__skip_switch\@
+alternative_else_nop_endif
+	mrs	\reg1, hcr_el2
+	and	\reg1, \reg1, #(HCR_ATA)
+	cbz	\reg1, .L__skip_switch\@
+
+	mrs_s	\reg1, SYS_RGSR_EL1
+	str	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
+	mrs_s	\reg1, SYS_GCR_EL1
+	str	\reg1, [\g_ctxt, #CPU_GCR_EL1]
+
+	ldr	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
+	msr_s	SYS_RGSR_EL1, \reg1
+	ldr	\reg1, [\h_ctxt, #CPU_GCR_EL1]
+	msr_s	SYS_GCR_EL1, \reg1
+
+.L__skip_switch\@:
+.endm
+
+#else /* CONFIG_ARM64_MTE */
+
+.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
+.endm
+
+.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
+.endm
+
+#endif /* CONFIG_ARM64_MTE */
+#endif /* __ASSEMBLY__ */
+#endif /* __ASM_KVM_MTE_H */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index dfd4edbfe360..5424d195cf96 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -580,7 +580,8 @@
 #define SCTLR_ELx_M	(BIT(0))
 
 #define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
-			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
+			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
+			 SCTLR_ELx_ITFSB)
 
 /* SCTLR_EL2 specific flags. */
 #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index a36e2fc330d4..944e4f1f45d9 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -108,6 +108,9 @@ int main(void)
   DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));
   DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
   DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
+  DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
+  DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
+  DEFINE(CPU_TFSRE0_EL1,	offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_EL1]));
   DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
   DEFINE(CPU_APIBKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
   DEFINE(CPU_APDAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index b0afad7a99c6..c67582c6dd55 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -13,6 +13,7 @@
 #include <asm/kvm_arm.h>
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmu.h>
+#include <asm/kvm_mte.h>
 #include <asm/kvm_ptrauth.h>
 
 	.text
@@ -51,6 +52,9 @@ alternative_else_nop_endif
 
 	add	x29, x0, #VCPU_CONTEXT
 
+	// mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
+	mte_switch_to_guest x29, x1, x2
+
 	// Macro ptrauth_switch_to_guest format:
 	// 	ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
 	// The below macro to restore guest keys is not implemented in C code
@@ -140,6 +144,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
 	// when this feature is enabled for kernel code.
 	ptrauth_switch_to_hyp x1, x2, x3, x4, x5
 
+	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
+	mte_switch_to_hyp x1, x2, x3
+
 	// Restore hyp's sp_el0
 	restore_sp_el0 x2, x3
 
diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
index cce43bfe158f..de7e14c862e6 100644
--- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
+++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
@@ -14,6 +14,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_hyp.h>
+#include <asm/kvm_mmu.h>
 
 static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
 {
@@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
 	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
 }
 
+static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
+{
+	struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
+
+	if (!vcpu)
+		vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
+
+	return kvm_has_mte(kern_hyp_va(vcpu->kvm));
+}
+
 static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 {
 	ctxt_sys_reg(ctxt, CSSELR_EL1)	= read_sysreg(csselr_el1);
@@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
 	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
 
+	if (ctxt_has_mte(ctxt)) {
+		ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
+		ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
+	}
+
 	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);
 	ctxt_sys_reg(ctxt, ELR_EL1)	= read_sysreg_el1(SYS_ELR);
 	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
@@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
 	write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),	par_el1);
 	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),	tpidr_el1);
 
+	if (ctxt_has_mte(ctxt)) {
+		write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
+		write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
+	}
+
 	if (!has_vhe() &&
 	    cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
 	    ctxt->__hyp_running_vcpu) {
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index e09dbc00b0a2..17cb6256f205 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1301,6 +1301,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	return true;
 }
 
+static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
+				   const struct sys_reg_desc *rd)
+{
+	return REG_HIDDEN;
+}
+
+#define MTE_REG(name) {				\
+	SYS_DESC(SYS_##name),			\
+	.access = undef_access,			\
+	.reset = reset_unknown,			\
+	.reg = name,				\
+	.visibility = mte_visibility,		\
+}
+
 /* sys_reg_desc initialiser for known cpufeature ID registers */
 #define ID_SANITISED(name) {			\
 	SYS_DESC(SYS_##name),			\
@@ -1469,8 +1483,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
 	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
 
-	{ SYS_DESC(SYS_RGSR_EL1), undef_access },
-	{ SYS_DESC(SYS_GCR_EL1), undef_access },
+	MTE_REG(RGSR_EL1),
+	MTE_REG(GCR_EL1),
 
 	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
 	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
@@ -1496,8 +1510,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
 	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
 
-	{ SYS_DESC(SYS_TFSR_EL1), undef_access },
-	{ SYS_DESC(SYS_TFSRE0_EL1), undef_access },
+	MTE_REG(TFSR_EL1),
+	MTE_REG(TFSRE0_EL1),
 
 	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
 	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
-- 
2.20.1

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

[PATCH v9 3/6] arm64: kvm: Save/restore MTE registers

[Steven Price]

Define the new system registers that MTE introduces and context switch
them. The MTE feature is still hidden from the ID register as it isn't
supported in a VM yet.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/kvm_host.h          |  6 ++
 arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
 arch/arm64/include/asm/sysreg.h            |  3 +-
 arch/arm64/kernel/asm-offsets.c            |  3 +
 arch/arm64/kvm/hyp/entry.S                 |  7 +++
 arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
 arch/arm64/kvm/sys_regs.c                  | 22 ++++++--
 7 files changed, 123 insertions(+), 5 deletions(-)
 create mode 100644 arch/arm64/include/asm/kvm_mte.h

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 1170ee137096..d00cc3590f6e 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -208,6 +208,12 @@ enum vcpu_sysreg {
 	CNTP_CVAL_EL0,
 	CNTP_CTL_EL0,
 
+	/* Memory Tagging Extension registers */
+	RGSR_EL1,	/* Random Allocation Tag Seed Register */
+	GCR_EL1,	/* Tag Control Register */
+	TFSR_EL1,	/* Tag Fault Status Register (EL1) */
+	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
+
 	/* 32bit specific registers. Keep them at the end of the range */
 	DACR32_EL2,	/* Domain Access Control Register */
 	IFSR32_EL2,	/* Instruction Fault Status Register */
diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
new file mode 100644
index 000000000000..6541c7d6ce06
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_mte.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 ARM Ltd.
+ */
+#ifndef __ASM_KVM_MTE_H
+#define __ASM_KVM_MTE_H
+
+#ifdef __ASSEMBLY__
+
+#include <asm/sysreg.h>
+
+#ifdef CONFIG_ARM64_MTE
+
+.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
+alternative_if_not ARM64_MTE
+	b	.L__skip_switch\@
+alternative_else_nop_endif
+	mrs	\reg1, hcr_el2
+	and	\reg1, \reg1, #(HCR_ATA)
+	cbz	\reg1, .L__skip_switch\@
+
+	mrs_s	\reg1, SYS_RGSR_EL1
+	str	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
+	mrs_s	\reg1, SYS_GCR_EL1
+	str	\reg1, [\h_ctxt, #CPU_GCR_EL1]
+
+	ldr	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
+	msr_s	SYS_RGSR_EL1, \reg1
+	ldr	\reg1, [\g_ctxt, #CPU_GCR_EL1]
+	msr_s	SYS_GCR_EL1, \reg1
+
+.L__skip_switch\@:
+.endm
+
+.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
+alternative_if_not ARM64_MTE
+	b	.L__skip_switch\@
+alternative_else_nop_endif
+	mrs	\reg1, hcr_el2
+	and	\reg1, \reg1, #(HCR_ATA)
+	cbz	\reg1, .L__skip_switch\@
+
+	mrs_s	\reg1, SYS_RGSR_EL1
+	str	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
+	mrs_s	\reg1, SYS_GCR_EL1
+	str	\reg1, [\g_ctxt, #CPU_GCR_EL1]
+
+	ldr	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
+	msr_s	SYS_RGSR_EL1, \reg1
+	ldr	\reg1, [\h_ctxt, #CPU_GCR_EL1]
+	msr_s	SYS_GCR_EL1, \reg1
+
+.L__skip_switch\@:
+.endm
+
+#else /* CONFIG_ARM64_MTE */
+
+.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
+.endm
+
+.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
+.endm
+
+#endif /* CONFIG_ARM64_MTE */
+#endif /* __ASSEMBLY__ */
+#endif /* __ASM_KVM_MTE_H */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index dfd4edbfe360..5424d195cf96 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -580,7 +580,8 @@
 #define SCTLR_ELx_M	(BIT(0))
 
 #define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
-			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
+			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
+			 SCTLR_ELx_ITFSB)
 
 /* SCTLR_EL2 specific flags. */
 #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index a36e2fc330d4..944e4f1f45d9 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -108,6 +108,9 @@ int main(void)
   DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));
   DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
   DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
+  DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
+  DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
+  DEFINE(CPU_TFSRE0_EL1,	offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_EL1]));
   DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
   DEFINE(CPU_APIBKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
   DEFINE(CPU_APDAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index b0afad7a99c6..c67582c6dd55 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -13,6 +13,7 @@
 #include <asm/kvm_arm.h>
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmu.h>
+#include <asm/kvm_mte.h>
 #include <asm/kvm_ptrauth.h>
 
 	.text
@@ -51,6 +52,9 @@ alternative_else_nop_endif
 
 	add	x29, x0, #VCPU_CONTEXT
 
+	// mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
+	mte_switch_to_guest x29, x1, x2
+
 	// Macro ptrauth_switch_to_guest format:
 	// 	ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
 	// The below macro to restore guest keys is not implemented in C code
@@ -140,6 +144,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
 	// when this feature is enabled for kernel code.
 	ptrauth_switch_to_hyp x1, x2, x3, x4, x5
 
+	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
+	mte_switch_to_hyp x1, x2, x3
+
 	// Restore hyp's sp_el0
 	restore_sp_el0 x2, x3
 
diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
index cce43bfe158f..de7e14c862e6 100644
--- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
+++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
@@ -14,6 +14,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_hyp.h>
+#include <asm/kvm_mmu.h>
 
 static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
 {
@@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
 	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
 }
 
+static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
+{
+	struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
+
+	if (!vcpu)
+		vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
+
+	return kvm_has_mte(kern_hyp_va(vcpu->kvm));
+}
+
 static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 {
 	ctxt_sys_reg(ctxt, CSSELR_EL1)	= read_sysreg(csselr_el1);
@@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
 	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
 
+	if (ctxt_has_mte(ctxt)) {
+		ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
+		ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
+	}
+
 	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);
 	ctxt_sys_reg(ctxt, ELR_EL1)	= read_sysreg_el1(SYS_ELR);
 	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
@@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
 	write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),	par_el1);
 	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),	tpidr_el1);
 
+	if (ctxt_has_mte(ctxt)) {
+		write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
+		write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
+	}
+
 	if (!has_vhe() &&
 	    cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
 	    ctxt->__hyp_running_vcpu) {
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index e09dbc00b0a2..17cb6256f205 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1301,6 +1301,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	return true;
 }
 
+static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
+				   const struct sys_reg_desc *rd)
+{
+	return REG_HIDDEN;
+}
+
+#define MTE_REG(name) {				\
+	SYS_DESC(SYS_##name),			\
+	.access = undef_access,			\
+	.reset = reset_unknown,			\
+	.reg = name,				\
+	.visibility = mte_visibility,		\
+}
+
 /* sys_reg_desc initialiser for known cpufeature ID registers */
 #define ID_SANITISED(name) {			\
 	SYS_DESC(SYS_##name),			\
@@ -1469,8 +1483,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
 	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
 
-	{ SYS_DESC(SYS_RGSR_EL1), undef_access },
-	{ SYS_DESC(SYS_GCR_EL1), undef_access },
+	MTE_REG(RGSR_EL1),
+	MTE_REG(GCR_EL1),
 
 	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
 	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
@@ -1496,8 +1510,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
 	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
 
-	{ SYS_DESC(SYS_TFSR_EL1), undef_access },
-	{ SYS_DESC(SYS_TFSRE0_EL1), undef_access },
+	MTE_REG(TFSR_EL1),
+	MTE_REG(TFSRE0_EL1),
 
 	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
 	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
-- 
2.20.1

Re: [PATCH v9 3/6] arm64: kvm: Save/restore MTE registers

[Marc Zyngier]

On Mon, 01 Mar 2021 14:23:12 +0000,
Steven Price <steven.price@arm.com> wrote:
> 
> Define the new system registers that MTE introduces and context switch
> them. The MTE feature is still hidden from the ID register as it isn't
> supported in a VM yet.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/asm/kvm_host.h          |  6 ++
>  arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
>  arch/arm64/include/asm/sysreg.h            |  3 +-
>  arch/arm64/kernel/asm-offsets.c            |  3 +
>  arch/arm64/kvm/hyp/entry.S                 |  7 +++
>  arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
>  arch/arm64/kvm/sys_regs.c                  | 22 ++++++--
>  7 files changed, 123 insertions(+), 5 deletions(-)
>  create mode 100644 arch/arm64/include/asm/kvm_mte.h
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 1170ee137096..d00cc3590f6e 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -208,6 +208,12 @@ enum vcpu_sysreg {
>  	CNTP_CVAL_EL0,
>  	CNTP_CTL_EL0,
>  
> +	/* Memory Tagging Extension registers */
> +	RGSR_EL1,	/* Random Allocation Tag Seed Register */
> +	GCR_EL1,	/* Tag Control Register */
> +	TFSR_EL1,	/* Tag Fault Status Register (EL1) */
> +	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
> +
>  	/* 32bit specific registers. Keep them at the end of the range */
>  	DACR32_EL2,	/* Domain Access Control Register */
>  	IFSR32_EL2,	/* Instruction Fault Status Register */
> diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
> new file mode 100644
> index 000000000000..6541c7d6ce06
> --- /dev/null
> +++ b/arch/arm64/include/asm/kvm_mte.h
> @@ -0,0 +1,66 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2020 ARM Ltd.
> + */
> +#ifndef __ASM_KVM_MTE_H
> +#define __ASM_KVM_MTE_H
> +
> +#ifdef __ASSEMBLY__
> +
> +#include <asm/sysreg.h>
> +
> +#ifdef CONFIG_ARM64_MTE
> +
> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
> +alternative_if_not ARM64_MTE
> +	b	.L__skip_switch\@
> +alternative_else_nop_endif
> +	mrs	\reg1, hcr_el2
> +	and	\reg1, \reg1, #(HCR_ATA)
> +	cbz	\reg1, .L__skip_switch\@
> +
> +	mrs_s	\reg1, SYS_RGSR_EL1
> +	str	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
> +	mrs_s	\reg1, SYS_GCR_EL1
> +	str	\reg1, [\h_ctxt, #CPU_GCR_EL1]
> +
> +	ldr	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
> +	msr_s	SYS_RGSR_EL1, \reg1
> +	ldr	\reg1, [\g_ctxt, #CPU_GCR_EL1]
> +	msr_s	SYS_GCR_EL1, \reg1
> +
> +.L__skip_switch\@:
> +.endm
> +
> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
> +alternative_if_not ARM64_MTE
> +	b	.L__skip_switch\@
> +alternative_else_nop_endif
> +	mrs	\reg1, hcr_el2
> +	and	\reg1, \reg1, #(HCR_ATA)
> +	cbz	\reg1, .L__skip_switch\@
> +
> +	mrs_s	\reg1, SYS_RGSR_EL1
> +	str	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
> +	mrs_s	\reg1, SYS_GCR_EL1
> +	str	\reg1, [\g_ctxt, #CPU_GCR_EL1]
> +
> +	ldr	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
> +	msr_s	SYS_RGSR_EL1, \reg1
> +	ldr	\reg1, [\h_ctxt, #CPU_GCR_EL1]
> +	msr_s	SYS_GCR_EL1, \reg1
> +
> +.L__skip_switch\@:
> +.endm
> +
> +#else /* CONFIG_ARM64_MTE */
> +
> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
> +.endm
> +
> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
> +.endm
> +
> +#endif /* CONFIG_ARM64_MTE */
> +#endif /* __ASSEMBLY__ */
> +#endif /* __ASM_KVM_MTE_H */
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index dfd4edbfe360..5424d195cf96 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -580,7 +580,8 @@
>  #define SCTLR_ELx_M	(BIT(0))
>  
>  #define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
> -			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
> +			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
> +			 SCTLR_ELx_ITFSB)
>  
>  /* SCTLR_EL2 specific flags. */
>  #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index a36e2fc330d4..944e4f1f45d9 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -108,6 +108,9 @@ int main(void)
>    DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));
>    DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
>    DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
> +  DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
> +  DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
> +  DEFINE(CPU_TFSRE0_EL1,	offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_EL1]));
>    DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
>    DEFINE(CPU_APIBKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
>    DEFINE(CPU_APDAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
> index b0afad7a99c6..c67582c6dd55 100644
> --- a/arch/arm64/kvm/hyp/entry.S
> +++ b/arch/arm64/kvm/hyp/entry.S
> @@ -13,6 +13,7 @@
>  #include <asm/kvm_arm.h>
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_mmu.h>
> +#include <asm/kvm_mte.h>
>  #include <asm/kvm_ptrauth.h>
>  
>  	.text
> @@ -51,6 +52,9 @@ alternative_else_nop_endif
>  
>  	add	x29, x0, #VCPU_CONTEXT
>  
> +	// mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
> +	mte_switch_to_guest x29, x1, x2
> +
>  	// Macro ptrauth_switch_to_guest format:
>  	// 	ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
>  	// The below macro to restore guest keys is not implemented in C code
> @@ -140,6 +144,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
>  	// when this feature is enabled for kernel code.
>  	ptrauth_switch_to_hyp x1, x2, x3, x4, x5
>  
> +	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
> +	mte_switch_to_hyp x1, x2, x3
> +
>  	// Restore hyp's sp_el0
>  	restore_sp_el0 x2, x3
>  
> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> index cce43bfe158f..de7e14c862e6 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> @@ -14,6 +14,7 @@
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_emulate.h>
>  #include <asm/kvm_hyp.h>
> +#include <asm/kvm_mmu.h>
>  
>  static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
>  {
> @@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
>  	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
>  }
>  
> +static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
> +{
> +	struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
> +
> +	if (!vcpu)
> +		vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
> +
> +	return kvm_has_mte(kern_hyp_va(vcpu->kvm));
> +}
> +
>  static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>  {
>  	ctxt_sys_reg(ctxt, CSSELR_EL1)	= read_sysreg(csselr_el1);
> @@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>  	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
>  	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
>  
> +	if (ctxt_has_mte(ctxt)) {
> +		ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
> +		ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
> +	}

Could TFSRE0_EL1 be synchronised on vcpu_load()/vcpu_put() instead of
being done eagerly on each save/restore? Same thing for TFSR_EL1 when
running VHE?

I'd like to keep the switch as lean as possible. I'm pretty sure this
would simplify some of the "container_of()" ugliness above.

> +
>  	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);
>  	ctxt_sys_reg(ctxt, ELR_EL1)	= read_sysreg_el1(SYS_ELR);
>  	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
> @@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
>  	write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),	par_el1);
>  	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),	tpidr_el1);
>  
> +	if (ctxt_has_mte(ctxt)) {
> +		write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
> +		write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
> +	}
> +
>  	if (!has_vhe() &&
>  	    cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
>  	    ctxt->__hyp_running_vcpu) {
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index e09dbc00b0a2..17cb6256f205 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1301,6 +1301,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>  	return true;
>  }
>  
> +static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
> +				   const struct sys_reg_desc *rd)
> +{
> +	return REG_HIDDEN;
> +}
> +
> +#define MTE_REG(name) {				\
> +	SYS_DESC(SYS_##name),			\
> +	.access = undef_access,			\
> +	.reset = reset_unknown,			\
> +	.reg = name,				\
> +	.visibility = mte_visibility,		\
> +}
> +
>  /* sys_reg_desc initialiser for known cpufeature ID registers */
>  #define ID_SANITISED(name) {			\
>  	SYS_DESC(SYS_##name),			\
> @@ -1469,8 +1483,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
>  	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
>  
> -	{ SYS_DESC(SYS_RGSR_EL1), undef_access },
> -	{ SYS_DESC(SYS_GCR_EL1), undef_access },
> +	MTE_REG(RGSR_EL1),
> +	MTE_REG(GCR_EL1),
>  
>  	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
>  	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
> @@ -1496,8 +1510,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
>  	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
>  
> -	{ SYS_DESC(SYS_TFSR_EL1), undef_access },
> -	{ SYS_DESC(SYS_TFSRE0_EL1), undef_access },
> +	MTE_REG(TFSR_EL1),
> +	MTE_REG(TFSRE0_EL1),
>  
>  	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
>  	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

Re: [PATCH v9 3/6] arm64: kvm: Save/restore MTE registers

[Marc Zyngier]

On Mon, 01 Mar 2021 14:23:12 +0000,
Steven Price <steven.price@arm.com> wrote:
> 
> Define the new system registers that MTE introduces and context switch
> them. The MTE feature is still hidden from the ID register as it isn't
> supported in a VM yet.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/asm/kvm_host.h          |  6 ++
>  arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
>  arch/arm64/include/asm/sysreg.h            |  3 +-
>  arch/arm64/kernel/asm-offsets.c            |  3 +
>  arch/arm64/kvm/hyp/entry.S                 |  7 +++
>  arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
>  arch/arm64/kvm/sys_regs.c                  | 22 ++++++--
>  7 files changed, 123 insertions(+), 5 deletions(-)
>  create mode 100644 arch/arm64/include/asm/kvm_mte.h
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 1170ee137096..d00cc3590f6e 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -208,6 +208,12 @@ enum vcpu_sysreg {
>  	CNTP_CVAL_EL0,
>  	CNTP_CTL_EL0,
>  
> +	/* Memory Tagging Extension registers */
> +	RGSR_EL1,	/* Random Allocation Tag Seed Register */
> +	GCR_EL1,	/* Tag Control Register */
> +	TFSR_EL1,	/* Tag Fault Status Register (EL1) */
> +	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
> +
>  	/* 32bit specific registers. Keep them at the end of the range */
>  	DACR32_EL2,	/* Domain Access Control Register */
>  	IFSR32_EL2,	/* Instruction Fault Status Register */
> diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
> new file mode 100644
> index 000000000000..6541c7d6ce06
> --- /dev/null
> +++ b/arch/arm64/include/asm/kvm_mte.h
> @@ -0,0 +1,66 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2020 ARM Ltd.
> + */
> +#ifndef __ASM_KVM_MTE_H
> +#define __ASM_KVM_MTE_H
> +
> +#ifdef __ASSEMBLY__
> +
> +#include <asm/sysreg.h>
> +
> +#ifdef CONFIG_ARM64_MTE
> +
> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
> +alternative_if_not ARM64_MTE
> +	b	.L__skip_switch\@
> +alternative_else_nop_endif
> +	mrs	\reg1, hcr_el2
> +	and	\reg1, \reg1, #(HCR_ATA)
> +	cbz	\reg1, .L__skip_switch\@
> +
> +	mrs_s	\reg1, SYS_RGSR_EL1
> +	str	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
> +	mrs_s	\reg1, SYS_GCR_EL1
> +	str	\reg1, [\h_ctxt, #CPU_GCR_EL1]
> +
> +	ldr	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
> +	msr_s	SYS_RGSR_EL1, \reg1
> +	ldr	\reg1, [\g_ctxt, #CPU_GCR_EL1]
> +	msr_s	SYS_GCR_EL1, \reg1
> +
> +.L__skip_switch\@:
> +.endm
> +
> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
> +alternative_if_not ARM64_MTE
> +	b	.L__skip_switch\@
> +alternative_else_nop_endif
> +	mrs	\reg1, hcr_el2
> +	and	\reg1, \reg1, #(HCR_ATA)
> +	cbz	\reg1, .L__skip_switch\@
> +
> +	mrs_s	\reg1, SYS_RGSR_EL1
> +	str	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
> +	mrs_s	\reg1, SYS_GCR_EL1
> +	str	\reg1, [\g_ctxt, #CPU_GCR_EL1]
> +
> +	ldr	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
> +	msr_s	SYS_RGSR_EL1, \reg1
> +	ldr	\reg1, [\h_ctxt, #CPU_GCR_EL1]
> +	msr_s	SYS_GCR_EL1, \reg1
> +
> +.L__skip_switch\@:
> +.endm
> +
> +#else /* CONFIG_ARM64_MTE */
> +
> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
> +.endm
> +
> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
> +.endm
> +
> +#endif /* CONFIG_ARM64_MTE */
> +#endif /* __ASSEMBLY__ */
> +#endif /* __ASM_KVM_MTE_H */
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index dfd4edbfe360..5424d195cf96 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -580,7 +580,8 @@
>  #define SCTLR_ELx_M	(BIT(0))
>  
>  #define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
> -			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
> +			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
> +			 SCTLR_ELx_ITFSB)
>  
>  /* SCTLR_EL2 specific flags. */
>  #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index a36e2fc330d4..944e4f1f45d9 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -108,6 +108,9 @@ int main(void)
>    DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));
>    DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
>    DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
> +  DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
> +  DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
> +  DEFINE(CPU_TFSRE0_EL1,	offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_EL1]));
>    DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
>    DEFINE(CPU_APIBKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
>    DEFINE(CPU_APDAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
> index b0afad7a99c6..c67582c6dd55 100644
> --- a/arch/arm64/kvm/hyp/entry.S
> +++ b/arch/arm64/kvm/hyp/entry.S
> @@ -13,6 +13,7 @@
>  #include <asm/kvm_arm.h>
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_mmu.h>
> +#include <asm/kvm_mte.h>
>  #include <asm/kvm_ptrauth.h>
>  
>  	.text
> @@ -51,6 +52,9 @@ alternative_else_nop_endif
>  
>  	add	x29, x0, #VCPU_CONTEXT
>  
> +	// mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
> +	mte_switch_to_guest x29, x1, x2
> +
>  	// Macro ptrauth_switch_to_guest format:
>  	// 	ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
>  	// The below macro to restore guest keys is not implemented in C code
> @@ -140,6 +144,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
>  	// when this feature is enabled for kernel code.
>  	ptrauth_switch_to_hyp x1, x2, x3, x4, x5
>  
> +	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
> +	mte_switch_to_hyp x1, x2, x3
> +
>  	// Restore hyp's sp_el0
>  	restore_sp_el0 x2, x3
>  
> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> index cce43bfe158f..de7e14c862e6 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> @@ -14,6 +14,7 @@
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_emulate.h>
>  #include <asm/kvm_hyp.h>
> +#include <asm/kvm_mmu.h>
>  
>  static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
>  {
> @@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
>  	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
>  }
>  
> +static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
> +{
> +	struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
> +
> +	if (!vcpu)
> +		vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
> +
> +	return kvm_has_mte(kern_hyp_va(vcpu->kvm));
> +}
> +
>  static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>  {
>  	ctxt_sys_reg(ctxt, CSSELR_EL1)	= read_sysreg(csselr_el1);
> @@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>  	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
>  	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
>  
> +	if (ctxt_has_mte(ctxt)) {
> +		ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
> +		ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
> +	}

Could TFSRE0_EL1 be synchronised on vcpu_load()/vcpu_put() instead of
being done eagerly on each save/restore? Same thing for TFSR_EL1 when
running VHE?

I'd like to keep the switch as lean as possible. I'm pretty sure this
would simplify some of the "container_of()" ugliness above.

> +
>  	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);
>  	ctxt_sys_reg(ctxt, ELR_EL1)	= read_sysreg_el1(SYS_ELR);
>  	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
> @@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
>  	write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),	par_el1);
>  	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),	tpidr_el1);
>  
> +	if (ctxt_has_mte(ctxt)) {
> +		write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
> +		write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
> +	}
> +
>  	if (!has_vhe() &&
>  	    cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
>  	    ctxt->__hyp_running_vcpu) {
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index e09dbc00b0a2..17cb6256f205 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1301,6 +1301,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>  	return true;
>  }
>  
> +static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
> +				   const struct sys_reg_desc *rd)
> +{
> +	return REG_HIDDEN;
> +}
> +
> +#define MTE_REG(name) {				\
> +	SYS_DESC(SYS_##name),			\
> +	.access = undef_access,			\
> +	.reset = reset_unknown,			\
> +	.reg = name,				\
> +	.visibility = mte_visibility,		\
> +}
> +
>  /* sys_reg_desc initialiser for known cpufeature ID registers */
>  #define ID_SANITISED(name) {			\
>  	SYS_DESC(SYS_##name),			\
> @@ -1469,8 +1483,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
>  	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
>  
> -	{ SYS_DESC(SYS_RGSR_EL1), undef_access },
> -	{ SYS_DESC(SYS_GCR_EL1), undef_access },
> +	MTE_REG(RGSR_EL1),
> +	MTE_REG(GCR_EL1),
>  
>  	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
>  	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
> @@ -1496,8 +1510,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
>  	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
>  
> -	{ SYS_DESC(SYS_TFSR_EL1), undef_access },
> -	{ SYS_DESC(SYS_TFSRE0_EL1), undef_access },
> +	MTE_REG(TFSR_EL1),
> +	MTE_REG(TFSRE0_EL1),
>  
>  	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
>  	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },

Thanks,

	M.

-- 
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Re: [PATCH v9 3/6] arm64: kvm: Save/restore MTE registers

[Marc Zyngier]

On Mon, 01 Mar 2021 14:23:12 +0000,
Steven Price <steven.price@arm.com> wrote:
> 
> Define the new system registers that MTE introduces and context switch
> them. The MTE feature is still hidden from the ID register as it isn't
> supported in a VM yet.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/asm/kvm_host.h          |  6 ++
>  arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
>  arch/arm64/include/asm/sysreg.h            |  3 +-
>  arch/arm64/kernel/asm-offsets.c            |  3 +
>  arch/arm64/kvm/hyp/entry.S                 |  7 +++
>  arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
>  arch/arm64/kvm/sys_regs.c                  | 22 ++++++--
>  7 files changed, 123 insertions(+), 5 deletions(-)
>  create mode 100644 arch/arm64/include/asm/kvm_mte.h
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 1170ee137096..d00cc3590f6e 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -208,6 +208,12 @@ enum vcpu_sysreg {
>  	CNTP_CVAL_EL0,
>  	CNTP_CTL_EL0,
>  
> +	/* Memory Tagging Extension registers */
> +	RGSR_EL1,	/* Random Allocation Tag Seed Register */
> +	GCR_EL1,	/* Tag Control Register */
> +	TFSR_EL1,	/* Tag Fault Status Register (EL1) */
> +	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
> +
>  	/* 32bit specific registers. Keep them at the end of the range */
>  	DACR32_EL2,	/* Domain Access Control Register */
>  	IFSR32_EL2,	/* Instruction Fault Status Register */
> diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
> new file mode 100644
> index 000000000000..6541c7d6ce06
> --- /dev/null
> +++ b/arch/arm64/include/asm/kvm_mte.h
> @@ -0,0 +1,66 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2020 ARM Ltd.
> + */
> +#ifndef __ASM_KVM_MTE_H
> +#define __ASM_KVM_MTE_H
> +
> +#ifdef __ASSEMBLY__
> +
> +#include <asm/sysreg.h>
> +
> +#ifdef CONFIG_ARM64_MTE
> +
> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
> +alternative_if_not ARM64_MTE
> +	b	.L__skip_switch\@
> +alternative_else_nop_endif
> +	mrs	\reg1, hcr_el2
> +	and	\reg1, \reg1, #(HCR_ATA)
> +	cbz	\reg1, .L__skip_switch\@
> +
> +	mrs_s	\reg1, SYS_RGSR_EL1
> +	str	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
> +	mrs_s	\reg1, SYS_GCR_EL1
> +	str	\reg1, [\h_ctxt, #CPU_GCR_EL1]
> +
> +	ldr	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
> +	msr_s	SYS_RGSR_EL1, \reg1
> +	ldr	\reg1, [\g_ctxt, #CPU_GCR_EL1]
> +	msr_s	SYS_GCR_EL1, \reg1
> +
> +.L__skip_switch\@:
> +.endm
> +
> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
> +alternative_if_not ARM64_MTE
> +	b	.L__skip_switch\@
> +alternative_else_nop_endif
> +	mrs	\reg1, hcr_el2
> +	and	\reg1, \reg1, #(HCR_ATA)
> +	cbz	\reg1, .L__skip_switch\@
> +
> +	mrs_s	\reg1, SYS_RGSR_EL1
> +	str	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
> +	mrs_s	\reg1, SYS_GCR_EL1
> +	str	\reg1, [\g_ctxt, #CPU_GCR_EL1]
> +
> +	ldr	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
> +	msr_s	SYS_RGSR_EL1, \reg1
> +	ldr	\reg1, [\h_ctxt, #CPU_GCR_EL1]
> +	msr_s	SYS_GCR_EL1, \reg1
> +
> +.L__skip_switch\@:
> +.endm
> +
> +#else /* CONFIG_ARM64_MTE */
> +
> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
> +.endm
> +
> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
> +.endm
> +
> +#endif /* CONFIG_ARM64_MTE */
> +#endif /* __ASSEMBLY__ */
> +#endif /* __ASM_KVM_MTE_H */
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index dfd4edbfe360..5424d195cf96 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -580,7 +580,8 @@
>  #define SCTLR_ELx_M	(BIT(0))
>  
>  #define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
> -			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
> +			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
> +			 SCTLR_ELx_ITFSB)
>  
>  /* SCTLR_EL2 specific flags. */
>  #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index a36e2fc330d4..944e4f1f45d9 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -108,6 +108,9 @@ int main(void)
>    DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));
>    DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
>    DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
> +  DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
> +  DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
> +  DEFINE(CPU_TFSRE0_EL1,	offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_EL1]));
>    DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
>    DEFINE(CPU_APIBKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
>    DEFINE(CPU_APDAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
> index b0afad7a99c6..c67582c6dd55 100644
> --- a/arch/arm64/kvm/hyp/entry.S
> +++ b/arch/arm64/kvm/hyp/entry.S
> @@ -13,6 +13,7 @@
>  #include <asm/kvm_arm.h>
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_mmu.h>
> +#include <asm/kvm_mte.h>
>  #include <asm/kvm_ptrauth.h>
>  
>  	.text
> @@ -51,6 +52,9 @@ alternative_else_nop_endif
>  
>  	add	x29, x0, #VCPU_CONTEXT
>  
> +	// mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
> +	mte_switch_to_guest x29, x1, x2
> +
>  	// Macro ptrauth_switch_to_guest format:
>  	// 	ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
>  	// The below macro to restore guest keys is not implemented in C code
> @@ -140,6 +144,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
>  	// when this feature is enabled for kernel code.
>  	ptrauth_switch_to_hyp x1, x2, x3, x4, x5
>  
> +	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
> +	mte_switch_to_hyp x1, x2, x3
> +
>  	// Restore hyp's sp_el0
>  	restore_sp_el0 x2, x3
>  
> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> index cce43bfe158f..de7e14c862e6 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> @@ -14,6 +14,7 @@
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_emulate.h>
>  #include <asm/kvm_hyp.h>
> +#include <asm/kvm_mmu.h>
>  
>  static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
>  {
> @@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
>  	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
>  }
>  
> +static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
> +{
> +	struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
> +
> +	if (!vcpu)
> +		vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
> +
> +	return kvm_has_mte(kern_hyp_va(vcpu->kvm));
> +}
> +
>  static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>  {
>  	ctxt_sys_reg(ctxt, CSSELR_EL1)	= read_sysreg(csselr_el1);
> @@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>  	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
>  	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
>  
> +	if (ctxt_has_mte(ctxt)) {
> +		ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
> +		ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
> +	}

Could TFSRE0_EL1 be synchronised on vcpu_load()/vcpu_put() instead of
being done eagerly on each save/restore? Same thing for TFSR_EL1 when
running VHE?

I'd like to keep the switch as lean as possible. I'm pretty sure this
would simplify some of the "container_of()" ugliness above.

> +
>  	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);
>  	ctxt_sys_reg(ctxt, ELR_EL1)	= read_sysreg_el1(SYS_ELR);
>  	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
> @@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
>  	write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),	par_el1);
>  	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),	tpidr_el1);
>  
> +	if (ctxt_has_mte(ctxt)) {
> +		write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
> +		write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
> +	}
> +
>  	if (!has_vhe() &&
>  	    cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
>  	    ctxt->__hyp_running_vcpu) {
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index e09dbc00b0a2..17cb6256f205 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1301,6 +1301,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>  	return true;
>  }
>  
> +static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
> +				   const struct sys_reg_desc *rd)
> +{
> +	return REG_HIDDEN;
> +}
> +
> +#define MTE_REG(name) {				\
> +	SYS_DESC(SYS_##name),			\
> +	.access = undef_access,			\
> +	.reset = reset_unknown,			\
> +	.reg = name,				\
> +	.visibility = mte_visibility,		\
> +}
> +
>  /* sys_reg_desc initialiser for known cpufeature ID registers */
>  #define ID_SANITISED(name) {			\
>  	SYS_DESC(SYS_##name),			\
> @@ -1469,8 +1483,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
>  	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
>  
> -	{ SYS_DESC(SYS_RGSR_EL1), undef_access },
> -	{ SYS_DESC(SYS_GCR_EL1), undef_access },
> +	MTE_REG(RGSR_EL1),
> +	MTE_REG(GCR_EL1),
>  
>  	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
>  	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
> @@ -1496,8 +1510,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
>  	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
>  
> -	{ SYS_DESC(SYS_TFSR_EL1), undef_access },
> -	{ SYS_DESC(SYS_TFSRE0_EL1), undef_access },
> +	MTE_REG(TFSR_EL1),
> +	MTE_REG(TFSRE0_EL1),
>  
>  	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
>  	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },

Thanks,

	M.

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Re: [PATCH v9 3/6] arm64: kvm: Save/restore MTE registers

[Marc Zyngier]

On Mon, 01 Mar 2021 14:23:12 +0000,
Steven Price <steven.price@arm.com> wrote:
> 
> Define the new system registers that MTE introduces and context switch
> them. The MTE feature is still hidden from the ID register as it isn't
> supported in a VM yet.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/asm/kvm_host.h          |  6 ++
>  arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
>  arch/arm64/include/asm/sysreg.h            |  3 +-
>  arch/arm64/kernel/asm-offsets.c            |  3 +
>  arch/arm64/kvm/hyp/entry.S                 |  7 +++
>  arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
>  arch/arm64/kvm/sys_regs.c                  | 22 ++++++--
>  7 files changed, 123 insertions(+), 5 deletions(-)
>  create mode 100644 arch/arm64/include/asm/kvm_mte.h
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 1170ee137096..d00cc3590f6e 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -208,6 +208,12 @@ enum vcpu_sysreg {
>  	CNTP_CVAL_EL0,
>  	CNTP_CTL_EL0,
>  
> +	/* Memory Tagging Extension registers */
> +	RGSR_EL1,	/* Random Allocation Tag Seed Register */
> +	GCR_EL1,	/* Tag Control Register */
> +	TFSR_EL1,	/* Tag Fault Status Register (EL1) */
> +	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
> +
>  	/* 32bit specific registers. Keep them at the end of the range */
>  	DACR32_EL2,	/* Domain Access Control Register */
>  	IFSR32_EL2,	/* Instruction Fault Status Register */
> diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
> new file mode 100644
> index 000000000000..6541c7d6ce06
> --- /dev/null
> +++ b/arch/arm64/include/asm/kvm_mte.h
> @@ -0,0 +1,66 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2020 ARM Ltd.
> + */
> +#ifndef __ASM_KVM_MTE_H
> +#define __ASM_KVM_MTE_H
> +
> +#ifdef __ASSEMBLY__
> +
> +#include <asm/sysreg.h>
> +
> +#ifdef CONFIG_ARM64_MTE
> +
> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
> +alternative_if_not ARM64_MTE
> +	b	.L__skip_switch\@
> +alternative_else_nop_endif
> +	mrs	\reg1, hcr_el2
> +	and	\reg1, \reg1, #(HCR_ATA)
> +	cbz	\reg1, .L__skip_switch\@
> +
> +	mrs_s	\reg1, SYS_RGSR_EL1
> +	str	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
> +	mrs_s	\reg1, SYS_GCR_EL1
> +	str	\reg1, [\h_ctxt, #CPU_GCR_EL1]
> +
> +	ldr	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
> +	msr_s	SYS_RGSR_EL1, \reg1
> +	ldr	\reg1, [\g_ctxt, #CPU_GCR_EL1]
> +	msr_s	SYS_GCR_EL1, \reg1
> +
> +.L__skip_switch\@:
> +.endm
> +
> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
> +alternative_if_not ARM64_MTE
> +	b	.L__skip_switch\@
> +alternative_else_nop_endif
> +	mrs	\reg1, hcr_el2
> +	and	\reg1, \reg1, #(HCR_ATA)
> +	cbz	\reg1, .L__skip_switch\@
> +
> +	mrs_s	\reg1, SYS_RGSR_EL1
> +	str	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
> +	mrs_s	\reg1, SYS_GCR_EL1
> +	str	\reg1, [\g_ctxt, #CPU_GCR_EL1]
> +
> +	ldr	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
> +	msr_s	SYS_RGSR_EL1, \reg1
> +	ldr	\reg1, [\h_ctxt, #CPU_GCR_EL1]
> +	msr_s	SYS_GCR_EL1, \reg1
> +
> +.L__skip_switch\@:
> +.endm
> +
> +#else /* CONFIG_ARM64_MTE */
> +
> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
> +.endm
> +
> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
> +.endm
> +
> +#endif /* CONFIG_ARM64_MTE */
> +#endif /* __ASSEMBLY__ */
> +#endif /* __ASM_KVM_MTE_H */
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index dfd4edbfe360..5424d195cf96 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -580,7 +580,8 @@
>  #define SCTLR_ELx_M	(BIT(0))
>  
>  #define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
> -			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
> +			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
> +			 SCTLR_ELx_ITFSB)
>  
>  /* SCTLR_EL2 specific flags. */
>  #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index a36e2fc330d4..944e4f1f45d9 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -108,6 +108,9 @@ int main(void)
>    DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));
>    DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
>    DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
> +  DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
> +  DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
> +  DEFINE(CPU_TFSRE0_EL1,	offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_EL1]));
>    DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
>    DEFINE(CPU_APIBKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
>    DEFINE(CPU_APDAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
> index b0afad7a99c6..c67582c6dd55 100644
> --- a/arch/arm64/kvm/hyp/entry.S
> +++ b/arch/arm64/kvm/hyp/entry.S
> @@ -13,6 +13,7 @@
>  #include <asm/kvm_arm.h>
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_mmu.h>
> +#include <asm/kvm_mte.h>
>  #include <asm/kvm_ptrauth.h>
>  
>  	.text
> @@ -51,6 +52,9 @@ alternative_else_nop_endif
>  
>  	add	x29, x0, #VCPU_CONTEXT
>  
> +	// mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
> +	mte_switch_to_guest x29, x1, x2
> +
>  	// Macro ptrauth_switch_to_guest format:
>  	// 	ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
>  	// The below macro to restore guest keys is not implemented in C code
> @@ -140,6 +144,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
>  	// when this feature is enabled for kernel code.
>  	ptrauth_switch_to_hyp x1, x2, x3, x4, x5
>  
> +	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
> +	mte_switch_to_hyp x1, x2, x3
> +
>  	// Restore hyp's sp_el0
>  	restore_sp_el0 x2, x3
>  
> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> index cce43bfe158f..de7e14c862e6 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> @@ -14,6 +14,7 @@
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_emulate.h>
>  #include <asm/kvm_hyp.h>
> +#include <asm/kvm_mmu.h>
>  
>  static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
>  {
> @@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
>  	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
>  }
>  
> +static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
> +{
> +	struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
> +
> +	if (!vcpu)
> +		vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
> +
> +	return kvm_has_mte(kern_hyp_va(vcpu->kvm));
> +}
> +
>  static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>  {
>  	ctxt_sys_reg(ctxt, CSSELR_EL1)	= read_sysreg(csselr_el1);
> @@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>  	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
>  	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
>  
> +	if (ctxt_has_mte(ctxt)) {
> +		ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
> +		ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
> +	}

Could TFSRE0_EL1 be synchronised on vcpu_load()/vcpu_put() instead of
being done eagerly on each save/restore? Same thing for TFSR_EL1 when
running VHE?

I'd like to keep the switch as lean as possible. I'm pretty sure this
would simplify some of the "container_of()" ugliness above.

> +
>  	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);
>  	ctxt_sys_reg(ctxt, ELR_EL1)	= read_sysreg_el1(SYS_ELR);
>  	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
> @@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
>  	write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),	par_el1);
>  	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),	tpidr_el1);
>  
> +	if (ctxt_has_mte(ctxt)) {
> +		write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
> +		write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
> +	}
> +
>  	if (!has_vhe() &&
>  	    cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
>  	    ctxt->__hyp_running_vcpu) {
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index e09dbc00b0a2..17cb6256f205 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1301,6 +1301,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>  	return true;
>  }
>  
> +static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
> +				   const struct sys_reg_desc *rd)
> +{
> +	return REG_HIDDEN;
> +}
> +
> +#define MTE_REG(name) {				\
> +	SYS_DESC(SYS_##name),			\
> +	.access = undef_access,			\
> +	.reset = reset_unknown,			\
> +	.reg = name,				\
> +	.visibility = mte_visibility,		\
> +}
> +
>  /* sys_reg_desc initialiser for known cpufeature ID registers */
>  #define ID_SANITISED(name) {			\
>  	SYS_DESC(SYS_##name),			\
> @@ -1469,8 +1483,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
>  	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
>  
> -	{ SYS_DESC(SYS_RGSR_EL1), undef_access },
> -	{ SYS_DESC(SYS_GCR_EL1), undef_access },
> +	MTE_REG(RGSR_EL1),
> +	MTE_REG(GCR_EL1),
>  
>  	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
>  	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
> @@ -1496,8 +1510,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
>  	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
>  
> -	{ SYS_DESC(SYS_TFSR_EL1), undef_access },
> -	{ SYS_DESC(SYS_TFSRE0_EL1), undef_access },
> +	MTE_REG(TFSR_EL1),
> +	MTE_REG(TFSRE0_EL1),
>  
>  	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
>  	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

Re: [PATCH v9 3/6] arm64: kvm: Save/restore MTE registers

[Steven Price]

On 09/03/2021 17:27, Marc Zyngier wrote:
> On Mon, 01 Mar 2021 14:23:12 +0000,
> Steven Price <steven.price@arm.com> wrote:
>>
>> Define the new system registers that MTE introduces and context switch
>> them. The MTE feature is still hidden from the ID register as it isn't
>> supported in a VM yet.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/asm/kvm_host.h          |  6 ++
>>   arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
>>   arch/arm64/include/asm/sysreg.h            |  3 +-
>>   arch/arm64/kernel/asm-offsets.c            |  3 +
>>   arch/arm64/kvm/hyp/entry.S                 |  7 +++
>>   arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
>>   arch/arm64/kvm/sys_regs.c                  | 22 ++++++--
>>   7 files changed, 123 insertions(+), 5 deletions(-)
>>   create mode 100644 arch/arm64/include/asm/kvm_mte.h
>>
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 1170ee137096..d00cc3590f6e 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -208,6 +208,12 @@ enum vcpu_sysreg {
>>   	CNTP_CVAL_EL0,
>>   	CNTP_CTL_EL0,
>>   
>> +	/* Memory Tagging Extension registers */
>> +	RGSR_EL1,	/* Random Allocation Tag Seed Register */
>> +	GCR_EL1,	/* Tag Control Register */
>> +	TFSR_EL1,	/* Tag Fault Status Register (EL1) */
>> +	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
>> +
>>   	/* 32bit specific registers. Keep them at the end of the range */
>>   	DACR32_EL2,	/* Domain Access Control Register */
>>   	IFSR32_EL2,	/* Instruction Fault Status Register */
>> diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
>> new file mode 100644
>> index 000000000000..6541c7d6ce06
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/kvm_mte.h
>> @@ -0,0 +1,66 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * Copyright (C) 2020 ARM Ltd.
>> + */
>> +#ifndef __ASM_KVM_MTE_H
>> +#define __ASM_KVM_MTE_H
>> +
>> +#ifdef __ASSEMBLY__
>> +
>> +#include <asm/sysreg.h>
>> +
>> +#ifdef CONFIG_ARM64_MTE
>> +
>> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
>> +alternative_if_not ARM64_MTE
>> +	b	.L__skip_switch\@
>> +alternative_else_nop_endif
>> +	mrs	\reg1, hcr_el2
>> +	and	\reg1, \reg1, #(HCR_ATA)
>> +	cbz	\reg1, .L__skip_switch\@
>> +
>> +	mrs_s	\reg1, SYS_RGSR_EL1
>> +	str	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
>> +	mrs_s	\reg1, SYS_GCR_EL1
>> +	str	\reg1, [\h_ctxt, #CPU_GCR_EL1]
>> +
>> +	ldr	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
>> +	msr_s	SYS_RGSR_EL1, \reg1
>> +	ldr	\reg1, [\g_ctxt, #CPU_GCR_EL1]
>> +	msr_s	SYS_GCR_EL1, \reg1
>> +
>> +.L__skip_switch\@:
>> +.endm
>> +
>> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
>> +alternative_if_not ARM64_MTE
>> +	b	.L__skip_switch\@
>> +alternative_else_nop_endif
>> +	mrs	\reg1, hcr_el2
>> +	and	\reg1, \reg1, #(HCR_ATA)
>> +	cbz	\reg1, .L__skip_switch\@
>> +
>> +	mrs_s	\reg1, SYS_RGSR_EL1
>> +	str	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
>> +	mrs_s	\reg1, SYS_GCR_EL1
>> +	str	\reg1, [\g_ctxt, #CPU_GCR_EL1]
>> +
>> +	ldr	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
>> +	msr_s	SYS_RGSR_EL1, \reg1
>> +	ldr	\reg1, [\h_ctxt, #CPU_GCR_EL1]
>> +	msr_s	SYS_GCR_EL1, \reg1
>> +
>> +.L__skip_switch\@:
>> +.endm
>> +
>> +#else /* CONFIG_ARM64_MTE */
>> +
>> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
>> +.endm
>> +
>> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
>> +.endm
>> +
>> +#endif /* CONFIG_ARM64_MTE */
>> +#endif /* __ASSEMBLY__ */
>> +#endif /* __ASM_KVM_MTE_H */
>> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
>> index dfd4edbfe360..5424d195cf96 100644
>> --- a/arch/arm64/include/asm/sysreg.h
>> +++ b/arch/arm64/include/asm/sysreg.h
>> @@ -580,7 +580,8 @@
>>   #define SCTLR_ELx_M	(BIT(0))
>>   
>>   #define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
>> -			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
>> +			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
>> +			 SCTLR_ELx_ITFSB)
>>   
>>   /* SCTLR_EL2 specific flags. */
>>   #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
>> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
>> index a36e2fc330d4..944e4f1f45d9 100644
>> --- a/arch/arm64/kernel/asm-offsets.c
>> +++ b/arch/arm64/kernel/asm-offsets.c
>> @@ -108,6 +108,9 @@ int main(void)
>>     DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));
>>     DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
>>     DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
>> +  DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
>> +  DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
>> +  DEFINE(CPU_TFSRE0_EL1,	offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_EL1]));
>>     DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
>>     DEFINE(CPU_APIBKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
>>     DEFINE(CPU_APDAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
>> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
>> index b0afad7a99c6..c67582c6dd55 100644
>> --- a/arch/arm64/kvm/hyp/entry.S
>> +++ b/arch/arm64/kvm/hyp/entry.S
>> @@ -13,6 +13,7 @@
>>   #include <asm/kvm_arm.h>
>>   #include <asm/kvm_asm.h>
>>   #include <asm/kvm_mmu.h>
>> +#include <asm/kvm_mte.h>
>>   #include <asm/kvm_ptrauth.h>
>>   
>>   	.text
>> @@ -51,6 +52,9 @@ alternative_else_nop_endif
>>   
>>   	add	x29, x0, #VCPU_CONTEXT
>>   
>> +	// mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
>> +	mte_switch_to_guest x29, x1, x2
>> +
>>   	// Macro ptrauth_switch_to_guest format:
>>   	// 	ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
>>   	// The below macro to restore guest keys is not implemented in C code
>> @@ -140,6 +144,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
>>   	// when this feature is enabled for kernel code.
>>   	ptrauth_switch_to_hyp x1, x2, x3, x4, x5
>>   
>> +	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
>> +	mte_switch_to_hyp x1, x2, x3
>> +
>>   	// Restore hyp's sp_el0
>>   	restore_sp_el0 x2, x3
>>   
>> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
>> index cce43bfe158f..de7e14c862e6 100644
>> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
>> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
>> @@ -14,6 +14,7 @@
>>   #include <asm/kvm_asm.h>
>>   #include <asm/kvm_emulate.h>
>>   #include <asm/kvm_hyp.h>
>> +#include <asm/kvm_mmu.h>
>>   
>>   static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
>>   {
>> @@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
>>   	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
>>   }
>>   
>> +static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
>> +{
>> +	struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
>> +
>> +	if (!vcpu)
>> +		vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
>> +
>> +	return kvm_has_mte(kern_hyp_va(vcpu->kvm));
>> +}
>> +
>>   static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>>   {
>>   	ctxt_sys_reg(ctxt, CSSELR_EL1)	= read_sysreg(csselr_el1);
>> @@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>>   	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
>>   	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
>>   
>> +	if (ctxt_has_mte(ctxt)) {
>> +		ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
>> +		ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
>> +	}
> 
> Could TFSRE0_EL1 be synchronised on vcpu_load()/vcpu_put() instead of
> being done eagerly on each save/restore? Same thing for TFSR_EL1 when
> running VHE?

For TFSR_EL1 + VHE I believe it is synchronised only on vcpu_load/put - 
__sysreg_save_el1_state() is called from kvm_vcpu_load_sysregs_vhe().

TFSRE0_EL1 potentially could be improved. I have to admit I was unsure 
if it should be in __sysreg_save_user_state() instead. However AFAICT 
that is called at the same time as __sysreg_save_el1_state() and there's 
no optimisation for nVHE. And given it's an _EL1 register this seemed 
like the logic place.

Am I missing something here? Potentially there are other registers to be 
optimised (TPIDRRO_EL0 looks like a possiblity), but IMHO that doesn't 
belong in this series.

 > I'd like to keep the switch as lean as possible. I'm pretty sure this
 > would simplify some of the "container_of()" ugliness above.

Yeah the container_of() isn't pretty - the alternative would be to stop 
treating __hyp_running_vcpu as a flag (instead add a real boolean for if 
the context is host/guest) and have it always point to the VCPU. I'm 
happy to make the change if you'd prefer it, but the downside is 
bloating the context unnecessarily.

Thanks,

Steve

>> +
>>   	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);
>>   	ctxt_sys_reg(ctxt, ELR_EL1)	= read_sysreg_el1(SYS_ELR);
>>   	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
>> @@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
>>   	write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),	par_el1);
>>   	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),	tpidr_el1);
>>   
>> +	if (ctxt_has_mte(ctxt)) {
>> +		write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
>> +		write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
>> +	}
>> +
>>   	if (!has_vhe() &&
>>   	    cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
>>   	    ctxt->__hyp_running_vcpu) {
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index e09dbc00b0a2..17cb6256f205 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -1301,6 +1301,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>>   	return true;
>>   }
>>   
>> +static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
>> +				   const struct sys_reg_desc *rd)
>> +{
>> +	return REG_HIDDEN;
>> +}
>> +
>> +#define MTE_REG(name) {				\
>> +	SYS_DESC(SYS_##name),			\
>> +	.access = undef_access,			\
>> +	.reset = reset_unknown,			\
>> +	.reg = name,				\
>> +	.visibility = mte_visibility,		\
>> +}
>> +
>>   /* sys_reg_desc initialiser for known cpufeature ID registers */
>>   #define ID_SANITISED(name) {			\
>>   	SYS_DESC(SYS_##name),			\
>> @@ -1469,8 +1483,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>>   	{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
>>   	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
>>   
>> -	{ SYS_DESC(SYS_RGSR_EL1), undef_access },
>> -	{ SYS_DESC(SYS_GCR_EL1), undef_access },
>> +	MTE_REG(RGSR_EL1),
>> +	MTE_REG(GCR_EL1),
>>   
>>   	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
>>   	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
>> @@ -1496,8 +1510,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>>   	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
>>   	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
>>   
>> -	{ SYS_DESC(SYS_TFSR_EL1), undef_access },
>> -	{ SYS_DESC(SYS_TFSRE0_EL1), undef_access },
>> +	MTE_REG(TFSR_EL1),
>> +	MTE_REG(TFSRE0_EL1),
>>   
>>   	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
>>   	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
> 
> Thanks,
> 
> 	M.
> 

Re: [PATCH v9 3/6] arm64: kvm: Save/restore MTE registers

[Steven Price]

On 09/03/2021 17:27, Marc Zyngier wrote:
> On Mon, 01 Mar 2021 14:23:12 +0000,
> Steven Price <steven.price@arm.com> wrote:
>>
>> Define the new system registers that MTE introduces and context switch
>> them. The MTE feature is still hidden from the ID register as it isn't
>> supported in a VM yet.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/asm/kvm_host.h          |  6 ++
>>   arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
>>   arch/arm64/include/asm/sysreg.h            |  3 +-
>>   arch/arm64/kernel/asm-offsets.c            |  3 +
>>   arch/arm64/kvm/hyp/entry.S                 |  7 +++
>>   arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
>>   arch/arm64/kvm/sys_regs.c                  | 22 ++++++--
>>   7 files changed, 123 insertions(+), 5 deletions(-)
>>   create mode 100644 arch/arm64/include/asm/kvm_mte.h
>>
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 1170ee137096..d00cc3590f6e 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -208,6 +208,12 @@ enum vcpu_sysreg {
>>   	CNTP_CVAL_EL0,
>>   	CNTP_CTL_EL0,
>>   
>> +	/* Memory Tagging Extension registers */
>> +	RGSR_EL1,	/* Random Allocation Tag Seed Register */
>> +	GCR_EL1,	/* Tag Control Register */
>> +	TFSR_EL1,	/* Tag Fault Status Register (EL1) */
>> +	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
>> +
>>   	/* 32bit specific registers. Keep them at the end of the range */
>>   	DACR32_EL2,	/* Domain Access Control Register */
>>   	IFSR32_EL2,	/* Instruction Fault Status Register */
>> diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
>> new file mode 100644
>> index 000000000000..6541c7d6ce06
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/kvm_mte.h
>> @@ -0,0 +1,66 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * Copyright (C) 2020 ARM Ltd.
>> + */
>> +#ifndef __ASM_KVM_MTE_H
>> +#define __ASM_KVM_MTE_H
>> +
>> +#ifdef __ASSEMBLY__
>> +
>> +#include <asm/sysreg.h>
>> +
>> +#ifdef CONFIG_ARM64_MTE
>> +
>> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
>> +alternative_if_not ARM64_MTE
>> +	b	.L__skip_switch\@
>> +alternative_else_nop_endif
>> +	mrs	\reg1, hcr_el2
>> +	and	\reg1, \reg1, #(HCR_ATA)
>> +	cbz	\reg1, .L__skip_switch\@
>> +
>> +	mrs_s	\reg1, SYS_RGSR_EL1
>> +	str	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
>> +	mrs_s	\reg1, SYS_GCR_EL1
>> +	str	\reg1, [\h_ctxt, #CPU_GCR_EL1]
>> +
>> +	ldr	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
>> +	msr_s	SYS_RGSR_EL1, \reg1
>> +	ldr	\reg1, [\g_ctxt, #CPU_GCR_EL1]
>> +	msr_s	SYS_GCR_EL1, \reg1
>> +
>> +.L__skip_switch\@:
>> +.endm
>> +
>> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
>> +alternative_if_not ARM64_MTE
>> +	b	.L__skip_switch\@
>> +alternative_else_nop_endif
>> +	mrs	\reg1, hcr_el2
>> +	and	\reg1, \reg1, #(HCR_ATA)
>> +	cbz	\reg1, .L__skip_switch\@
>> +
>> +	mrs_s	\reg1, SYS_RGSR_EL1
>> +	str	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
>> +	mrs_s	\reg1, SYS_GCR_EL1
>> +	str	\reg1, [\g_ctxt, #CPU_GCR_EL1]
>> +
>> +	ldr	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
>> +	msr_s	SYS_RGSR_EL1, \reg1
>> +	ldr	\reg1, [\h_ctxt, #CPU_GCR_EL1]
>> +	msr_s	SYS_GCR_EL1, \reg1
>> +
>> +.L__skip_switch\@:
>> +.endm
>> +
>> +#else /* CONFIG_ARM64_MTE */
>> +
>> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
>> +.endm
>> +
>> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
>> +.endm
>> +
>> +#endif /* CONFIG_ARM64_MTE */
>> +#endif /* __ASSEMBLY__ */
>> +#endif /* __ASM_KVM_MTE_H */
>> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
>> index dfd4edbfe360..5424d195cf96 100644
>> --- a/arch/arm64/include/asm/sysreg.h
>> +++ b/arch/arm64/include/asm/sysreg.h
>> @@ -580,7 +580,8 @@
>>   #define SCTLR_ELx_M	(BIT(0))
>>   
>>   #define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
>> -			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
>> +			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
>> +			 SCTLR_ELx_ITFSB)
>>   
>>   /* SCTLR_EL2 specific flags. */
>>   #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
>> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
>> index a36e2fc330d4..944e4f1f45d9 100644
>> --- a/arch/arm64/kernel/asm-offsets.c
>> +++ b/arch/arm64/kernel/asm-offsets.c
>> @@ -108,6 +108,9 @@ int main(void)
>>     DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));
>>     DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
>>     DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
>> +  DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
>> +  DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
>> +  DEFINE(CPU_TFSRE0_EL1,	offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_EL1]));
>>     DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
>>     DEFINE(CPU_APIBKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
>>     DEFINE(CPU_APDAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
>> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
>> index b0afad7a99c6..c67582c6dd55 100644
>> --- a/arch/arm64/kvm/hyp/entry.S
>> +++ b/arch/arm64/kvm/hyp/entry.S
>> @@ -13,6 +13,7 @@
>>   #include <asm/kvm_arm.h>
>>   #include <asm/kvm_asm.h>
>>   #include <asm/kvm_mmu.h>
>> +#include <asm/kvm_mte.h>
>>   #include <asm/kvm_ptrauth.h>
>>   
>>   	.text
>> @@ -51,6 +52,9 @@ alternative_else_nop_endif
>>   
>>   	add	x29, x0, #VCPU_CONTEXT
>>   
>> +	// mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
>> +	mte_switch_to_guest x29, x1, x2
>> +
>>   	// Macro ptrauth_switch_to_guest format:
>>   	// 	ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
>>   	// The below macro to restore guest keys is not implemented in C code
>> @@ -140,6 +144,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
>>   	// when this feature is enabled for kernel code.
>>   	ptrauth_switch_to_hyp x1, x2, x3, x4, x5
>>   
>> +	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
>> +	mte_switch_to_hyp x1, x2, x3
>> +
>>   	// Restore hyp's sp_el0
>>   	restore_sp_el0 x2, x3
>>   
>> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
>> index cce43bfe158f..de7e14c862e6 100644
>> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
>> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
>> @@ -14,6 +14,7 @@
>>   #include <asm/kvm_asm.h>
>>   #include <asm/kvm_emulate.h>
>>   #include <asm/kvm_hyp.h>
>> +#include <asm/kvm_mmu.h>
>>   
>>   static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
>>   {
>> @@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
>>   	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
>>   }
>>   
>> +static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
>> +{
>> +	struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
>> +
>> +	if (!vcpu)
>> +		vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
>> +
>> +	return kvm_has_mte(kern_hyp_va(vcpu->kvm));
>> +}
>> +
>>   static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>>   {
>>   	ctxt_sys_reg(ctxt, CSSELR_EL1)	= read_sysreg(csselr_el1);
>> @@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>>   	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
>>   	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
>>   
>> +	if (ctxt_has_mte(ctxt)) {
>> +		ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
>> +		ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
>> +	}
> 
> Could TFSRE0_EL1 be synchronised on vcpu_load()/vcpu_put() instead of
> being done eagerly on each save/restore? Same thing for TFSR_EL1 when
> running VHE?

For TFSR_EL1 + VHE I believe it is synchronised only on vcpu_load/put - 
__sysreg_save_el1_state() is called from kvm_vcpu_load_sysregs_vhe().

TFSRE0_EL1 potentially could be improved. I have to admit I was unsure 
if it should be in __sysreg_save_user_state() instead. However AFAICT 
that is called at the same time as __sysreg_save_el1_state() and there's 
no optimisation for nVHE. And given it's an _EL1 register this seemed 
like the logic place.

Am I missing something here? Potentially there are other registers to be 
optimised (TPIDRRO_EL0 looks like a possiblity), but IMHO that doesn't 
belong in this series.

 > I'd like to keep the switch as lean as possible. I'm pretty sure this
 > would simplify some of the "container_of()" ugliness above.

Yeah the container_of() isn't pretty - the alternative would be to stop 
treating __hyp_running_vcpu as a flag (instead add a real boolean for if 
the context is host/guest) and have it always point to the VCPU. I'm 
happy to make the change if you'd prefer it, but the downside is 
bloating the context unnecessarily.

Thanks,

Steve

>> +
>>   	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);
>>   	ctxt_sys_reg(ctxt, ELR_EL1)	= read_sysreg_el1(SYS_ELR);
>>   	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
>> @@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
>>   	write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),	par_el1);
>>   	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),	tpidr_el1);
>>   
>> +	if (ctxt_has_mte(ctxt)) {
>> +		write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
>> +		write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
>> +	}
>> +
>>   	if (!has_vhe() &&
>>   	    cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
>>   	    ctxt->__hyp_running_vcpu) {
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index e09dbc00b0a2..17cb6256f205 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -1301,6 +1301,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>>   	return true;
>>   }
>>   
>> +static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
>> +				   const struct sys_reg_desc *rd)
>> +{
>> +	return REG_HIDDEN;
>> +}
>> +
>> +#define MTE_REG(name) {				\
>> +	SYS_DESC(SYS_##name),			\
>> +	.access = undef_access,			\
>> +	.reset = reset_unknown,			\
>> +	.reg = name,				\
>> +	.visibility = mte_visibility,		\
>> +}
>> +
>>   /* sys_reg_desc initialiser for known cpufeature ID registers */
>>   #define ID_SANITISED(name) {			\
>>   	SYS_DESC(SYS_##name),			\
>> @@ -1469,8 +1483,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>>   	{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
>>   	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
>>   
>> -	{ SYS_DESC(SYS_RGSR_EL1), undef_access },
>> -	{ SYS_DESC(SYS_GCR_EL1), undef_access },
>> +	MTE_REG(RGSR_EL1),
>> +	MTE_REG(GCR_EL1),
>>   
>>   	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
>>   	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
>> @@ -1496,8 +1510,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>>   	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
>>   	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
>>   
>> -	{ SYS_DESC(SYS_TFSR_EL1), undef_access },
>> -	{ SYS_DESC(SYS_TFSRE0_EL1), undef_access },
>> +	MTE_REG(TFSR_EL1),
>> +	MTE_REG(TFSRE0_EL1),
>>   
>>   	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
>>   	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
> 
> Thanks,
> 
> 	M.
> 


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Re: [PATCH v9 3/6] arm64: kvm: Save/restore MTE registers

[Steven Price]

On 09/03/2021 17:27, Marc Zyngier wrote:
> On Mon, 01 Mar 2021 14:23:12 +0000,
> Steven Price <steven.price@arm.com> wrote:
>>
>> Define the new system registers that MTE introduces and context switch
>> them. The MTE feature is still hidden from the ID register as it isn't
>> supported in a VM yet.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/asm/kvm_host.h          |  6 ++
>>   arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
>>   arch/arm64/include/asm/sysreg.h            |  3 +-
>>   arch/arm64/kernel/asm-offsets.c            |  3 +
>>   arch/arm64/kvm/hyp/entry.S                 |  7 +++
>>   arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
>>   arch/arm64/kvm/sys_regs.c                  | 22 ++++++--
>>   7 files changed, 123 insertions(+), 5 deletions(-)
>>   create mode 100644 arch/arm64/include/asm/kvm_mte.h
>>
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 1170ee137096..d00cc3590f6e 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -208,6 +208,12 @@ enum vcpu_sysreg {
>>   	CNTP_CVAL_EL0,
>>   	CNTP_CTL_EL0,
>>   
>> +	/* Memory Tagging Extension registers */
>> +	RGSR_EL1,	/* Random Allocation Tag Seed Register */
>> +	GCR_EL1,	/* Tag Control Register */
>> +	TFSR_EL1,	/* Tag Fault Status Register (EL1) */
>> +	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
>> +
>>   	/* 32bit specific registers. Keep them at the end of the range */
>>   	DACR32_EL2,	/* Domain Access Control Register */
>>   	IFSR32_EL2,	/* Instruction Fault Status Register */
>> diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
>> new file mode 100644
>> index 000000000000..6541c7d6ce06
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/kvm_mte.h
>> @@ -0,0 +1,66 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * Copyright (C) 2020 ARM Ltd.
>> + */
>> +#ifndef __ASM_KVM_MTE_H
>> +#define __ASM_KVM_MTE_H
>> +
>> +#ifdef __ASSEMBLY__
>> +
>> +#include <asm/sysreg.h>
>> +
>> +#ifdef CONFIG_ARM64_MTE
>> +
>> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
>> +alternative_if_not ARM64_MTE
>> +	b	.L__skip_switch\@
>> +alternative_else_nop_endif
>> +	mrs	\reg1, hcr_el2
>> +	and	\reg1, \reg1, #(HCR_ATA)
>> +	cbz	\reg1, .L__skip_switch\@
>> +
>> +	mrs_s	\reg1, SYS_RGSR_EL1
>> +	str	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
>> +	mrs_s	\reg1, SYS_GCR_EL1
>> +	str	\reg1, [\h_ctxt, #CPU_GCR_EL1]
>> +
>> +	ldr	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
>> +	msr_s	SYS_RGSR_EL1, \reg1
>> +	ldr	\reg1, [\g_ctxt, #CPU_GCR_EL1]
>> +	msr_s	SYS_GCR_EL1, \reg1
>> +
>> +.L__skip_switch\@:
>> +.endm
>> +
>> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
>> +alternative_if_not ARM64_MTE
>> +	b	.L__skip_switch\@
>> +alternative_else_nop_endif
>> +	mrs	\reg1, hcr_el2
>> +	and	\reg1, \reg1, #(HCR_ATA)
>> +	cbz	\reg1, .L__skip_switch\@
>> +
>> +	mrs_s	\reg1, SYS_RGSR_EL1
>> +	str	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
>> +	mrs_s	\reg1, SYS_GCR_EL1
>> +	str	\reg1, [\g_ctxt, #CPU_GCR_EL1]
>> +
>> +	ldr	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
>> +	msr_s	SYS_RGSR_EL1, \reg1
>> +	ldr	\reg1, [\h_ctxt, #CPU_GCR_EL1]
>> +	msr_s	SYS_GCR_EL1, \reg1
>> +
>> +.L__skip_switch\@:
>> +.endm
>> +
>> +#else /* CONFIG_ARM64_MTE */
>> +
>> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
>> +.endm
>> +
>> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
>> +.endm
>> +
>> +#endif /* CONFIG_ARM64_MTE */
>> +#endif /* __ASSEMBLY__ */
>> +#endif /* __ASM_KVM_MTE_H */
>> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
>> index dfd4edbfe360..5424d195cf96 100644
>> --- a/arch/arm64/include/asm/sysreg.h
>> +++ b/arch/arm64/include/asm/sysreg.h
>> @@ -580,7 +580,8 @@
>>   #define SCTLR_ELx_M	(BIT(0))
>>   
>>   #define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
>> -			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
>> +			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
>> +			 SCTLR_ELx_ITFSB)
>>   
>>   /* SCTLR_EL2 specific flags. */
>>   #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
>> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
>> index a36e2fc330d4..944e4f1f45d9 100644
>> --- a/arch/arm64/kernel/asm-offsets.c
>> +++ b/arch/arm64/kernel/asm-offsets.c
>> @@ -108,6 +108,9 @@ int main(void)
>>     DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));
>>     DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
>>     DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
>> +  DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
>> +  DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
>> +  DEFINE(CPU_TFSRE0_EL1,	offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_EL1]));
>>     DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
>>     DEFINE(CPU_APIBKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
>>     DEFINE(CPU_APDAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
>> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
>> index b0afad7a99c6..c67582c6dd55 100644
>> --- a/arch/arm64/kvm/hyp/entry.S
>> +++ b/arch/arm64/kvm/hyp/entry.S
>> @@ -13,6 +13,7 @@
>>   #include <asm/kvm_arm.h>
>>   #include <asm/kvm_asm.h>
>>   #include <asm/kvm_mmu.h>
>> +#include <asm/kvm_mte.h>
>>   #include <asm/kvm_ptrauth.h>
>>   
>>   	.text
>> @@ -51,6 +52,9 @@ alternative_else_nop_endif
>>   
>>   	add	x29, x0, #VCPU_CONTEXT
>>   
>> +	// mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
>> +	mte_switch_to_guest x29, x1, x2
>> +
>>   	// Macro ptrauth_switch_to_guest format:
>>   	// 	ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
>>   	// The below macro to restore guest keys is not implemented in C code
>> @@ -140,6 +144,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
>>   	// when this feature is enabled for kernel code.
>>   	ptrauth_switch_to_hyp x1, x2, x3, x4, x5
>>   
>> +	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
>> +	mte_switch_to_hyp x1, x2, x3
>> +
>>   	// Restore hyp's sp_el0
>>   	restore_sp_el0 x2, x3
>>   
>> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
>> index cce43bfe158f..de7e14c862e6 100644
>> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
>> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
>> @@ -14,6 +14,7 @@
>>   #include <asm/kvm_asm.h>
>>   #include <asm/kvm_emulate.h>
>>   #include <asm/kvm_hyp.h>
>> +#include <asm/kvm_mmu.h>
>>   
>>   static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
>>   {
>> @@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
>>   	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
>>   }
>>   
>> +static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
>> +{
>> +	struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
>> +
>> +	if (!vcpu)
>> +		vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
>> +
>> +	return kvm_has_mte(kern_hyp_va(vcpu->kvm));
>> +}
>> +
>>   static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>>   {
>>   	ctxt_sys_reg(ctxt, CSSELR_EL1)	= read_sysreg(csselr_el1);
>> @@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>>   	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
>>   	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
>>   
>> +	if (ctxt_has_mte(ctxt)) {
>> +		ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
>> +		ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
>> +	}
> 
> Could TFSRE0_EL1 be synchronised on vcpu_load()/vcpu_put() instead of
> being done eagerly on each save/restore? Same thing for TFSR_EL1 when
> running VHE?

For TFSR_EL1 + VHE I believe it is synchronised only on vcpu_load/put - 
__sysreg_save_el1_state() is called from kvm_vcpu_load_sysregs_vhe().

TFSRE0_EL1 potentially could be improved. I have to admit I was unsure 
if it should be in __sysreg_save_user_state() instead. However AFAICT 
that is called at the same time as __sysreg_save_el1_state() and there's 
no optimisation for nVHE. And given it's an _EL1 register this seemed 
like the logic place.

Am I missing something here? Potentially there are other registers to be 
optimised (TPIDRRO_EL0 looks like a possiblity), but IMHO that doesn't 
belong in this series.

 > I'd like to keep the switch as lean as possible. I'm pretty sure this
 > would simplify some of the "container_of()" ugliness above.

Yeah the container_of() isn't pretty - the alternative would be to stop 
treating __hyp_running_vcpu as a flag (instead add a real boolean for if 
the context is host/guest) and have it always point to the VCPU. I'm 
happy to make the change if you'd prefer it, but the downside is 
bloating the context unnecessarily.

Thanks,

Steve

>> +
>>   	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);
>>   	ctxt_sys_reg(ctxt, ELR_EL1)	= read_sysreg_el1(SYS_ELR);
>>   	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
>> @@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
>>   	write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),	par_el1);
>>   	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),	tpidr_el1);
>>   
>> +	if (ctxt_has_mte(ctxt)) {
>> +		write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
>> +		write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
>> +	}
>> +
>>   	if (!has_vhe() &&
>>   	    cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
>>   	    ctxt->__hyp_running_vcpu) {
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index e09dbc00b0a2..17cb6256f205 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -1301,6 +1301,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>>   	return true;
>>   }
>>   
>> +static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
>> +				   const struct sys_reg_desc *rd)
>> +{
>> +	return REG_HIDDEN;
>> +}
>> +
>> +#define MTE_REG(name) {				\
>> +	SYS_DESC(SYS_##name),			\
>> +	.access = undef_access,			\
>> +	.reset = reset_unknown,			\
>> +	.reg = name,				\
>> +	.visibility = mte_visibility,		\
>> +}
>> +
>>   /* sys_reg_desc initialiser for known cpufeature ID registers */
>>   #define ID_SANITISED(name) {			\
>>   	SYS_DESC(SYS_##name),			\
>> @@ -1469,8 +1483,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>>   	{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
>>   	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
>>   
>> -	{ SYS_DESC(SYS_RGSR_EL1), undef_access },
>> -	{ SYS_DESC(SYS_GCR_EL1), undef_access },
>> +	MTE_REG(RGSR_EL1),
>> +	MTE_REG(GCR_EL1),
>>   
>>   	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
>>   	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
>> @@ -1496,8 +1510,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>>   	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
>>   	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
>>   
>> -	{ SYS_DESC(SYS_TFSR_EL1), undef_access },
>> -	{ SYS_DESC(SYS_TFSRE0_EL1), undef_access },
>> +	MTE_REG(TFSR_EL1),
>> +	MTE_REG(TFSRE0_EL1),
>>   
>>   	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
>>   	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
> 
> Thanks,
> 
> 	M.
> 

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Re: [PATCH v9 3/6] arm64: kvm: Save/restore MTE registers

[Steven Price]

On 09/03/2021 17:27, Marc Zyngier wrote:
> On Mon, 01 Mar 2021 14:23:12 +0000,
> Steven Price <steven.price@arm.com> wrote:
>>
>> Define the new system registers that MTE introduces and context switch
>> them. The MTE feature is still hidden from the ID register as it isn't
>> supported in a VM yet.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/asm/kvm_host.h          |  6 ++
>>   arch/arm64/include/asm/kvm_mte.h           | 66 ++++++++++++++++++++++
>>   arch/arm64/include/asm/sysreg.h            |  3 +-
>>   arch/arm64/kernel/asm-offsets.c            |  3 +
>>   arch/arm64/kvm/hyp/entry.S                 |  7 +++
>>   arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
>>   arch/arm64/kvm/sys_regs.c                  | 22 ++++++--
>>   7 files changed, 123 insertions(+), 5 deletions(-)
>>   create mode 100644 arch/arm64/include/asm/kvm_mte.h
>>
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 1170ee137096..d00cc3590f6e 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -208,6 +208,12 @@ enum vcpu_sysreg {
>>   	CNTP_CVAL_EL0,
>>   	CNTP_CTL_EL0,
>>   
>> +	/* Memory Tagging Extension registers */
>> +	RGSR_EL1,	/* Random Allocation Tag Seed Register */
>> +	GCR_EL1,	/* Tag Control Register */
>> +	TFSR_EL1,	/* Tag Fault Status Register (EL1) */
>> +	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
>> +
>>   	/* 32bit specific registers. Keep them at the end of the range */
>>   	DACR32_EL2,	/* Domain Access Control Register */
>>   	IFSR32_EL2,	/* Instruction Fault Status Register */
>> diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
>> new file mode 100644
>> index 000000000000..6541c7d6ce06
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/kvm_mte.h
>> @@ -0,0 +1,66 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * Copyright (C) 2020 ARM Ltd.
>> + */
>> +#ifndef __ASM_KVM_MTE_H
>> +#define __ASM_KVM_MTE_H
>> +
>> +#ifdef __ASSEMBLY__
>> +
>> +#include <asm/sysreg.h>
>> +
>> +#ifdef CONFIG_ARM64_MTE
>> +
>> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
>> +alternative_if_not ARM64_MTE
>> +	b	.L__skip_switch\@
>> +alternative_else_nop_endif
>> +	mrs	\reg1, hcr_el2
>> +	and	\reg1, \reg1, #(HCR_ATA)
>> +	cbz	\reg1, .L__skip_switch\@
>> +
>> +	mrs_s	\reg1, SYS_RGSR_EL1
>> +	str	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
>> +	mrs_s	\reg1, SYS_GCR_EL1
>> +	str	\reg1, [\h_ctxt, #CPU_GCR_EL1]
>> +
>> +	ldr	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
>> +	msr_s	SYS_RGSR_EL1, \reg1
>> +	ldr	\reg1, [\g_ctxt, #CPU_GCR_EL1]
>> +	msr_s	SYS_GCR_EL1, \reg1
>> +
>> +.L__skip_switch\@:
>> +.endm
>> +
>> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
>> +alternative_if_not ARM64_MTE
>> +	b	.L__skip_switch\@
>> +alternative_else_nop_endif
>> +	mrs	\reg1, hcr_el2
>> +	and	\reg1, \reg1, #(HCR_ATA)
>> +	cbz	\reg1, .L__skip_switch\@
>> +
>> +	mrs_s	\reg1, SYS_RGSR_EL1
>> +	str	\reg1, [\g_ctxt, #CPU_RGSR_EL1]
>> +	mrs_s	\reg1, SYS_GCR_EL1
>> +	str	\reg1, [\g_ctxt, #CPU_GCR_EL1]
>> +
>> +	ldr	\reg1, [\h_ctxt, #CPU_RGSR_EL1]
>> +	msr_s	SYS_RGSR_EL1, \reg1
>> +	ldr	\reg1, [\h_ctxt, #CPU_GCR_EL1]
>> +	msr_s	SYS_GCR_EL1, \reg1
>> +
>> +.L__skip_switch\@:
>> +.endm
>> +
>> +#else /* CONFIG_ARM64_MTE */
>> +
>> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
>> +.endm
>> +
>> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
>> +.endm
>> +
>> +#endif /* CONFIG_ARM64_MTE */
>> +#endif /* __ASSEMBLY__ */
>> +#endif /* __ASM_KVM_MTE_H */
>> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
>> index dfd4edbfe360..5424d195cf96 100644
>> --- a/arch/arm64/include/asm/sysreg.h
>> +++ b/arch/arm64/include/asm/sysreg.h
>> @@ -580,7 +580,8 @@
>>   #define SCTLR_ELx_M	(BIT(0))
>>   
>>   #define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
>> -			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
>> +			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
>> +			 SCTLR_ELx_ITFSB)
>>   
>>   /* SCTLR_EL2 specific flags. */
>>   #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
>> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
>> index a36e2fc330d4..944e4f1f45d9 100644
>> --- a/arch/arm64/kernel/asm-offsets.c
>> +++ b/arch/arm64/kernel/asm-offsets.c
>> @@ -108,6 +108,9 @@ int main(void)
>>     DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));
>>     DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
>>     DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
>> +  DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
>> +  DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
>> +  DEFINE(CPU_TFSRE0_EL1,	offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_EL1]));
>>     DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
>>     DEFINE(CPU_APIBKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
>>     DEFINE(CPU_APDAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
>> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
>> index b0afad7a99c6..c67582c6dd55 100644
>> --- a/arch/arm64/kvm/hyp/entry.S
>> +++ b/arch/arm64/kvm/hyp/entry.S
>> @@ -13,6 +13,7 @@
>>   #include <asm/kvm_arm.h>
>>   #include <asm/kvm_asm.h>
>>   #include <asm/kvm_mmu.h>
>> +#include <asm/kvm_mte.h>
>>   #include <asm/kvm_ptrauth.h>
>>   
>>   	.text
>> @@ -51,6 +52,9 @@ alternative_else_nop_endif
>>   
>>   	add	x29, x0, #VCPU_CONTEXT
>>   
>> +	// mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
>> +	mte_switch_to_guest x29, x1, x2
>> +
>>   	// Macro ptrauth_switch_to_guest format:
>>   	// 	ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
>>   	// The below macro to restore guest keys is not implemented in C code
>> @@ -140,6 +144,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
>>   	// when this feature is enabled for kernel code.
>>   	ptrauth_switch_to_hyp x1, x2, x3, x4, x5
>>   
>> +	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
>> +	mte_switch_to_hyp x1, x2, x3
>> +
>>   	// Restore hyp's sp_el0
>>   	restore_sp_el0 x2, x3
>>   
>> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
>> index cce43bfe158f..de7e14c862e6 100644
>> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
>> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
>> @@ -14,6 +14,7 @@
>>   #include <asm/kvm_asm.h>
>>   #include <asm/kvm_emulate.h>
>>   #include <asm/kvm_hyp.h>
>> +#include <asm/kvm_mmu.h>
>>   
>>   static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
>>   {
>> @@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
>>   	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
>>   }
>>   
>> +static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
>> +{
>> +	struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
>> +
>> +	if (!vcpu)
>> +		vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
>> +
>> +	return kvm_has_mte(kern_hyp_va(vcpu->kvm));
>> +}
>> +
>>   static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>>   {
>>   	ctxt_sys_reg(ctxt, CSSELR_EL1)	= read_sysreg(csselr_el1);
>> @@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>>   	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
>>   	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
>>   
>> +	if (ctxt_has_mte(ctxt)) {
>> +		ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
>> +		ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
>> +	}
> 
> Could TFSRE0_EL1 be synchronised on vcpu_load()/vcpu_put() instead of
> being done eagerly on each save/restore? Same thing for TFSR_EL1 when
> running VHE?

For TFSR_EL1 + VHE I believe it is synchronised only on vcpu_load/put - 
__sysreg_save_el1_state() is called from kvm_vcpu_load_sysregs_vhe().

TFSRE0_EL1 potentially could be improved. I have to admit I was unsure 
if it should be in __sysreg_save_user_state() instead. However AFAICT 
that is called at the same time as __sysreg_save_el1_state() and there's 
no optimisation for nVHE. And given it's an _EL1 register this seemed 
like the logic place.

Am I missing something here? Potentially there are other registers to be 
optimised (TPIDRRO_EL0 looks like a possiblity), but IMHO that doesn't 
belong in this series.

 > I'd like to keep the switch as lean as possible. I'm pretty sure this
 > would simplify some of the "container_of()" ugliness above.

Yeah the container_of() isn't pretty - the alternative would be to stop 
treating __hyp_running_vcpu as a flag (instead add a real boolean for if 
the context is host/guest) and have it always point to the VCPU. I'm 
happy to make the change if you'd prefer it, but the downside is 
bloating the context unnecessarily.

Thanks,

Steve

>> +
>>   	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);
>>   	ctxt_sys_reg(ctxt, ELR_EL1)	= read_sysreg_el1(SYS_ELR);
>>   	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
>> @@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
>>   	write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),	par_el1);
>>   	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),	tpidr_el1);
>>   
>> +	if (ctxt_has_mte(ctxt)) {
>> +		write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
>> +		write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
>> +	}
>> +
>>   	if (!has_vhe() &&
>>   	    cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
>>   	    ctxt->__hyp_running_vcpu) {
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index e09dbc00b0a2..17cb6256f205 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -1301,6 +1301,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>>   	return true;
>>   }
>>   
>> +static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
>> +				   const struct sys_reg_desc *rd)
>> +{
>> +	return REG_HIDDEN;
>> +}
>> +
>> +#define MTE_REG(name) {				\
>> +	SYS_DESC(SYS_##name),			\
>> +	.access = undef_access,			\
>> +	.reset = reset_unknown,			\
>> +	.reg = name,				\
>> +	.visibility = mte_visibility,		\
>> +}
>> +
>>   /* sys_reg_desc initialiser for known cpufeature ID registers */
>>   #define ID_SANITISED(name) {			\
>>   	SYS_DESC(SYS_##name),			\
>> @@ -1469,8 +1483,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>>   	{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
>>   	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
>>   
>> -	{ SYS_DESC(SYS_RGSR_EL1), undef_access },
>> -	{ SYS_DESC(SYS_GCR_EL1), undef_access },
>> +	MTE_REG(RGSR_EL1),
>> +	MTE_REG(GCR_EL1),
>>   
>>   	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
>>   	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
>> @@ -1496,8 +1510,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>>   	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
>>   	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
>>   
>> -	{ SYS_DESC(SYS_TFSR_EL1), undef_access },
>> -	{ SYS_DESC(SYS_TFSRE0_EL1), undef_access },
>> +	MTE_REG(TFSR_EL1),
>> +	MTE_REG(TFSRE0_EL1),
>>   
>>   	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
>>   	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
> 
> Thanks,
> 
> 	M.
> 

[PATCH v9 4/6] arm64: kvm: Expose KVM_ARM_CAP_MTE

[Steven Price]

It's now safe for the VMM to enable MTE in a guest, so expose the
capability to user space.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/kvm/arm.c      | 9 +++++++++
 arch/arm64/kvm/sys_regs.c | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index fc4c95dd2d26..46bf319f6cb7 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -93,6 +93,12 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 		r = 0;
 		kvm->arch.return_nisv_io_abort_to_user = true;
 		break;
+	case KVM_CAP_ARM_MTE:
+		if (!system_supports_mte() || kvm->created_vcpus)
+			return -EINVAL;
+		r = 0;
+		kvm->arch.mte_enabled = true;
+		break;
 	default:
 		r = -EINVAL;
 		break;
@@ -234,6 +240,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		 */
 		r = 1;
 		break;
+	case KVM_CAP_ARM_MTE:
+		r = system_supports_mte();
+		break;
 	case KVM_CAP_STEAL_TIME:
 		r = kvm_arm_pvtime_supported();
 		break;
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 17cb6256f205..5793499334e3 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1304,6 +1304,9 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
 				   const struct sys_reg_desc *rd)
 {
+	if (kvm_has_mte(vcpu->kvm))
+		return 0;
+
 	return REG_HIDDEN;
 }
 
-- 
2.20.1

[PATCH v9 4/6] arm64: kvm: Expose KVM_ARM_CAP_MTE

[Steven Price]

It's now safe for the VMM to enable MTE in a guest, so expose the
capability to user space.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/kvm/arm.c      | 9 +++++++++
 arch/arm64/kvm/sys_regs.c | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index fc4c95dd2d26..46bf319f6cb7 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -93,6 +93,12 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 		r = 0;
 		kvm->arch.return_nisv_io_abort_to_user = true;
 		break;
+	case KVM_CAP_ARM_MTE:
+		if (!system_supports_mte() || kvm->created_vcpus)
+			return -EINVAL;
+		r = 0;
+		kvm->arch.mte_enabled = true;
+		break;
 	default:
 		r = -EINVAL;
 		break;
@@ -234,6 +240,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		 */
 		r = 1;
 		break;
+	case KVM_CAP_ARM_MTE:
+		r = system_supports_mte();
+		break;
 	case KVM_CAP_STEAL_TIME:
 		r = kvm_arm_pvtime_supported();
 		break;
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 17cb6256f205..5793499334e3 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1304,6 +1304,9 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
 				   const struct sys_reg_desc *rd)
 {
+	if (kvm_has_mte(vcpu->kvm))
+		return 0;
+
 	return REG_HIDDEN;
 }
 
-- 
2.20.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v9 4/6] arm64: kvm: Expose KVM_ARM_CAP_MTE

[Steven Price]

It's now safe for the VMM to enable MTE in a guest, so expose the
capability to user space.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/kvm/arm.c      | 9 +++++++++
 arch/arm64/kvm/sys_regs.c | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index fc4c95dd2d26..46bf319f6cb7 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -93,6 +93,12 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 		r = 0;
 		kvm->arch.return_nisv_io_abort_to_user = true;
 		break;
+	case KVM_CAP_ARM_MTE:
+		if (!system_supports_mte() || kvm->created_vcpus)
+			return -EINVAL;
+		r = 0;
+		kvm->arch.mte_enabled = true;
+		break;
 	default:
 		r = -EINVAL;
 		break;
@@ -234,6 +240,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		 */
 		r = 1;
 		break;
+	case KVM_CAP_ARM_MTE:
+		r = system_supports_mte();
+		break;
 	case KVM_CAP_STEAL_TIME:
 		r = kvm_arm_pvtime_supported();
 		break;
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 17cb6256f205..5793499334e3 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1304,6 +1304,9 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
 				   const struct sys_reg_desc *rd)
 {
+	if (kvm_has_mte(vcpu->kvm))
+		return 0;
+
 	return REG_HIDDEN;
 }
 
-- 
2.20.1

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

[PATCH v9 4/6] arm64: kvm: Expose KVM_ARM_CAP_MTE

[Steven Price]

It's now safe for the VMM to enable MTE in a guest, so expose the
capability to user space.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/kvm/arm.c      | 9 +++++++++
 arch/arm64/kvm/sys_regs.c | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index fc4c95dd2d26..46bf319f6cb7 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -93,6 +93,12 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 		r = 0;
 		kvm->arch.return_nisv_io_abort_to_user = true;
 		break;
+	case KVM_CAP_ARM_MTE:
+		if (!system_supports_mte() || kvm->created_vcpus)
+			return -EINVAL;
+		r = 0;
+		kvm->arch.mte_enabled = true;
+		break;
 	default:
 		r = -EINVAL;
 		break;
@@ -234,6 +240,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		 */
 		r = 1;
 		break;
+	case KVM_CAP_ARM_MTE:
+		r = system_supports_mte();
+		break;
 	case KVM_CAP_STEAL_TIME:
 		r = kvm_arm_pvtime_supported();
 		break;
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 17cb6256f205..5793499334e3 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1304,6 +1304,9 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
 				   const struct sys_reg_desc *rd)
 {
+	if (kvm_has_mte(vcpu->kvm))
+		return 0;
+
 	return REG_HIDDEN;
 }
 
-- 
2.20.1

[PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest

[Steven Price]

The VMM may not wish to have it's own mapping of guest memory mapped
with PROT_MTE because this causes problems if the VMM has tag checking
enabled (the guest controls the tags in physical RAM and it's unlikely
the tags are correct for the VMM).

Instead add a new ioctl which allows the VMM to easily read/write the
tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
while the VMM can still read/write the tags for the purpose of
migration.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/uapi/asm/kvm.h | 13 +++++++
 arch/arm64/kvm/arm.c              | 57 +++++++++++++++++++++++++++++++
 include/uapi/linux/kvm.h          |  1 +
 3 files changed, 71 insertions(+)

diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 24223adae150..5fc2534ac5df 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -184,6 +184,19 @@ struct kvm_vcpu_events {
 	__u32 reserved[12];
 };
 
+struct kvm_arm_copy_mte_tags {
+	__u64 guest_ipa;
+	__u64 length;
+	union {
+		void __user *addr;
+		__u64 padding;
+	};
+	__u64 flags;
+};
+
+#define KVM_ARM_TAGS_TO_GUEST		0
+#define KVM_ARM_TAGS_FROM_GUEST		1
+
 /* If you need to interpret the index values, here is the key: */
 #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
 #define KVM_REG_ARM_COPROC_SHIFT	16
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 46bf319f6cb7..01d404833e24 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1297,6 +1297,53 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
 	}
 }
 
+static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
+				      struct kvm_arm_copy_mte_tags *copy_tags)
+{
+	gpa_t guest_ipa = copy_tags->guest_ipa;
+	size_t length = copy_tags->length;
+	void __user *tags = copy_tags->addr;
+	gpa_t gfn;
+	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
+
+	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
+		return -EINVAL;
+
+	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
+		return -EINVAL;
+
+	gfn = gpa_to_gfn(guest_ipa);
+
+	while (length > 0) {
+		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
+		void *maddr;
+		unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
+
+		if (is_error_noslot_pfn(pfn))
+			return -ENOENT;
+
+		maddr = page_address(pfn_to_page(pfn));
+
+		if (!write) {
+			num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
+			kvm_release_pfn_clean(pfn);
+		} else {
+			num_tags = mte_copy_tags_from_user(maddr, tags,
+							   num_tags);
+			kvm_release_pfn_dirty(pfn);
+		}
+
+		if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
+			return -EFAULT;
+
+		gfn++;
+		tags += num_tags;
+		length -= PAGE_SIZE;
+	}
+
+	return 0;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
@@ -1333,6 +1380,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
 
 		return 0;
 	}
+	case KVM_ARM_MTE_COPY_TAGS: {
+		struct kvm_arm_copy_mte_tags copy_tags;
+
+		if (!kvm_has_mte(kvm))
+			return -EINVAL;
+
+		if (copy_from_user(&copy_tags, argp, sizeof(copy_tags)))
+			return -EFAULT;
+		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
+	}
 	default:
 		return -EINVAL;
 	}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 05618a4abf7e..b75af0f9ba55 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1423,6 +1423,7 @@ struct kvm_s390_ucas_mapping {
 /* Available with KVM_CAP_PMU_EVENT_FILTER */
 #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
 #define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
+#define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
 
 /* ioctl for vm fd */
 #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
-- 
2.20.1

[PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest

[Steven Price]

The VMM may not wish to have it's own mapping of guest memory mapped
with PROT_MTE because this causes problems if the VMM has tag checking
enabled (the guest controls the tags in physical RAM and it's unlikely
the tags are correct for the VMM).

Instead add a new ioctl which allows the VMM to easily read/write the
tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
while the VMM can still read/write the tags for the purpose of
migration.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/uapi/asm/kvm.h | 13 +++++++
 arch/arm64/kvm/arm.c              | 57 +++++++++++++++++++++++++++++++
 include/uapi/linux/kvm.h          |  1 +
 3 files changed, 71 insertions(+)

diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 24223adae150..5fc2534ac5df 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -184,6 +184,19 @@ struct kvm_vcpu_events {
 	__u32 reserved[12];
 };
 
+struct kvm_arm_copy_mte_tags {
+	__u64 guest_ipa;
+	__u64 length;
+	union {
+		void __user *addr;
+		__u64 padding;
+	};
+	__u64 flags;
+};
+
+#define KVM_ARM_TAGS_TO_GUEST		0
+#define KVM_ARM_TAGS_FROM_GUEST		1
+
 /* If you need to interpret the index values, here is the key: */
 #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
 #define KVM_REG_ARM_COPROC_SHIFT	16
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 46bf319f6cb7..01d404833e24 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1297,6 +1297,53 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
 	}
 }
 
+static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
+				      struct kvm_arm_copy_mte_tags *copy_tags)
+{
+	gpa_t guest_ipa = copy_tags->guest_ipa;
+	size_t length = copy_tags->length;
+	void __user *tags = copy_tags->addr;
+	gpa_t gfn;
+	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
+
+	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
+		return -EINVAL;
+
+	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
+		return -EINVAL;
+
+	gfn = gpa_to_gfn(guest_ipa);
+
+	while (length > 0) {
+		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
+		void *maddr;
+		unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
+
+		if (is_error_noslot_pfn(pfn))
+			return -ENOENT;
+
+		maddr = page_address(pfn_to_page(pfn));
+
+		if (!write) {
+			num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
+			kvm_release_pfn_clean(pfn);
+		} else {
+			num_tags = mte_copy_tags_from_user(maddr, tags,
+							   num_tags);
+			kvm_release_pfn_dirty(pfn);
+		}
+
+		if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
+			return -EFAULT;
+
+		gfn++;
+		tags += num_tags;
+		length -= PAGE_SIZE;
+	}
+
+	return 0;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
@@ -1333,6 +1380,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
 
 		return 0;
 	}
+	case KVM_ARM_MTE_COPY_TAGS: {
+		struct kvm_arm_copy_mte_tags copy_tags;
+
+		if (!kvm_has_mte(kvm))
+			return -EINVAL;
+
+		if (copy_from_user(&copy_tags, argp, sizeof(copy_tags)))
+			return -EFAULT;
+		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
+	}
 	default:
 		return -EINVAL;
 	}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 05618a4abf7e..b75af0f9ba55 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1423,6 +1423,7 @@ struct kvm_s390_ucas_mapping {
 /* Available with KVM_CAP_PMU_EVENT_FILTER */
 #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
 #define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
+#define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
 
 /* ioctl for vm fd */
 #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
-- 
2.20.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest

[Steven Price]

The VMM may not wish to have it's own mapping of guest memory mapped
with PROT_MTE because this causes problems if the VMM has tag checking
enabled (the guest controls the tags in physical RAM and it's unlikely
the tags are correct for the VMM).

Instead add a new ioctl which allows the VMM to easily read/write the
tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
while the VMM can still read/write the tags for the purpose of
migration.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/uapi/asm/kvm.h | 13 +++++++
 arch/arm64/kvm/arm.c              | 57 +++++++++++++++++++++++++++++++
 include/uapi/linux/kvm.h          |  1 +
 3 files changed, 71 insertions(+)

diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 24223adae150..5fc2534ac5df 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -184,6 +184,19 @@ struct kvm_vcpu_events {
 	__u32 reserved[12];
 };
 
+struct kvm_arm_copy_mte_tags {
+	__u64 guest_ipa;
+	__u64 length;
+	union {
+		void __user *addr;
+		__u64 padding;
+	};
+	__u64 flags;
+};
+
+#define KVM_ARM_TAGS_TO_GUEST		0
+#define KVM_ARM_TAGS_FROM_GUEST		1
+
 /* If you need to interpret the index values, here is the key: */
 #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
 #define KVM_REG_ARM_COPROC_SHIFT	16
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 46bf319f6cb7..01d404833e24 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1297,6 +1297,53 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
 	}
 }
 
+static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
+				      struct kvm_arm_copy_mte_tags *copy_tags)
+{
+	gpa_t guest_ipa = copy_tags->guest_ipa;
+	size_t length = copy_tags->length;
+	void __user *tags = copy_tags->addr;
+	gpa_t gfn;
+	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
+
+	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
+		return -EINVAL;
+
+	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
+		return -EINVAL;
+
+	gfn = gpa_to_gfn(guest_ipa);
+
+	while (length > 0) {
+		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
+		void *maddr;
+		unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
+
+		if (is_error_noslot_pfn(pfn))
+			return -ENOENT;
+
+		maddr = page_address(pfn_to_page(pfn));
+
+		if (!write) {
+			num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
+			kvm_release_pfn_clean(pfn);
+		} else {
+			num_tags = mte_copy_tags_from_user(maddr, tags,
+							   num_tags);
+			kvm_release_pfn_dirty(pfn);
+		}
+
+		if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
+			return -EFAULT;
+
+		gfn++;
+		tags += num_tags;
+		length -= PAGE_SIZE;
+	}
+
+	return 0;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
@@ -1333,6 +1380,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
 
 		return 0;
 	}
+	case KVM_ARM_MTE_COPY_TAGS: {
+		struct kvm_arm_copy_mte_tags copy_tags;
+
+		if (!kvm_has_mte(kvm))
+			return -EINVAL;
+
+		if (copy_from_user(&copy_tags, argp, sizeof(copy_tags)))
+			return -EFAULT;
+		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
+	}
 	default:
 		return -EINVAL;
 	}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 05618a4abf7e..b75af0f9ba55 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1423,6 +1423,7 @@ struct kvm_s390_ucas_mapping {
 /* Available with KVM_CAP_PMU_EVENT_FILTER */
 #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
 #define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
+#define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
 
 /* ioctl for vm fd */
 #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
-- 
2.20.1

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

[PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest

[Steven Price]

The VMM may not wish to have it's own mapping of guest memory mapped
with PROT_MTE because this causes problems if the VMM has tag checking
enabled (the guest controls the tags in physical RAM and it's unlikely
the tags are correct for the VMM).

Instead add a new ioctl which allows the VMM to easily read/write the
tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
while the VMM can still read/write the tags for the purpose of
migration.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/uapi/asm/kvm.h | 13 +++++++
 arch/arm64/kvm/arm.c              | 57 +++++++++++++++++++++++++++++++
 include/uapi/linux/kvm.h          |  1 +
 3 files changed, 71 insertions(+)

diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 24223adae150..5fc2534ac5df 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -184,6 +184,19 @@ struct kvm_vcpu_events {
 	__u32 reserved[12];
 };
 
+struct kvm_arm_copy_mte_tags {
+	__u64 guest_ipa;
+	__u64 length;
+	union {
+		void __user *addr;
+		__u64 padding;
+	};
+	__u64 flags;
+};
+
+#define KVM_ARM_TAGS_TO_GUEST		0
+#define KVM_ARM_TAGS_FROM_GUEST		1
+
 /* If you need to interpret the index values, here is the key: */
 #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
 #define KVM_REG_ARM_COPROC_SHIFT	16
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 46bf319f6cb7..01d404833e24 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1297,6 +1297,53 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
 	}
 }
 
+static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
+				      struct kvm_arm_copy_mte_tags *copy_tags)
+{
+	gpa_t guest_ipa = copy_tags->guest_ipa;
+	size_t length = copy_tags->length;
+	void __user *tags = copy_tags->addr;
+	gpa_t gfn;
+	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
+
+	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
+		return -EINVAL;
+
+	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
+		return -EINVAL;
+
+	gfn = gpa_to_gfn(guest_ipa);
+
+	while (length > 0) {
+		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
+		void *maddr;
+		unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
+
+		if (is_error_noslot_pfn(pfn))
+			return -ENOENT;
+
+		maddr = page_address(pfn_to_page(pfn));
+
+		if (!write) {
+			num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
+			kvm_release_pfn_clean(pfn);
+		} else {
+			num_tags = mte_copy_tags_from_user(maddr, tags,
+							   num_tags);
+			kvm_release_pfn_dirty(pfn);
+		}
+
+		if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
+			return -EFAULT;
+
+		gfn++;
+		tags += num_tags;
+		length -= PAGE_SIZE;
+	}
+
+	return 0;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
@@ -1333,6 +1380,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
 
 		return 0;
 	}
+	case KVM_ARM_MTE_COPY_TAGS: {
+		struct kvm_arm_copy_mte_tags copy_tags;
+
+		if (!kvm_has_mte(kvm))
+			return -EINVAL;
+
+		if (copy_from_user(&copy_tags, argp, sizeof(copy_tags)))
+			return -EFAULT;
+		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
+	}
 	default:
 		return -EINVAL;
 	}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 05618a4abf7e..b75af0f9ba55 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1423,6 +1423,7 @@ struct kvm_s390_ucas_mapping {
 /* Available with KVM_CAP_PMU_EVENT_FILTER */
 #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
 #define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
+#define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
 
 /* ioctl for vm fd */
 #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
-- 
2.20.1

Re: [PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest

[Marc Zyngier]

On Mon, 01 Mar 2021 14:23:14 +0000,
Steven Price <steven.price@arm.com> wrote:
> 
> The VMM may not wish to have it's own mapping of guest memory mapped
> with PROT_MTE because this causes problems if the VMM has tag checking
> enabled (the guest controls the tags in physical RAM and it's unlikely
> the tags are correct for the VMM).
> 
> Instead add a new ioctl which allows the VMM to easily read/write the
> tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
> while the VMM can still read/write the tags for the purpose of
> migration.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/uapi/asm/kvm.h | 13 +++++++
>  arch/arm64/kvm/arm.c              | 57 +++++++++++++++++++++++++++++++
>  include/uapi/linux/kvm.h          |  1 +
>  3 files changed, 71 insertions(+)
> 
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 24223adae150..5fc2534ac5df 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -184,6 +184,19 @@ struct kvm_vcpu_events {
>  	__u32 reserved[12];
>  };
>  
> +struct kvm_arm_copy_mte_tags {
> +	__u64 guest_ipa;
> +	__u64 length;
> +	union {
> +		void __user *addr;
> +		__u64 padding;
> +	};
> +	__u64 flags;

I'd be keen on a couple of reserved __64s. Just in case...

> +};
> +
> +#define KVM_ARM_TAGS_TO_GUEST		0
> +#define KVM_ARM_TAGS_FROM_GUEST		1
> +
>  /* If you need to interpret the index values, here is the key: */
>  #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
>  #define KVM_REG_ARM_COPROC_SHIFT	16
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 46bf319f6cb7..01d404833e24 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1297,6 +1297,53 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
>  	}
>  }
>  
> +static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
> +				      struct kvm_arm_copy_mte_tags *copy_tags)
> +{
> +	gpa_t guest_ipa = copy_tags->guest_ipa;
> +	size_t length = copy_tags->length;
> +	void __user *tags = copy_tags->addr;
> +	gpa_t gfn;
> +	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
> +
> +	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
> +		return -EINVAL;
> +
> +	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
> +		return -EINVAL;

It is a bit odd to require userspace to provide a page-aligned
addr/size, as it now has to find out about the kernel's page
size. MTE_GRANULE_SIZE-aligned values would make more sense. Is there
an underlying reason for this?

> +
> +	gfn = gpa_to_gfn(guest_ipa);
> +
> +	while (length > 0) {
> +		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
> +		void *maddr;
> +		unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
> +
> +		if (is_error_noslot_pfn(pfn))
> +			return -ENOENT;
> +
> +		maddr = page_address(pfn_to_page(pfn));
> +
> +		if (!write) {
> +			num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
> +			kvm_release_pfn_clean(pfn);
> +		} else {
> +			num_tags = mte_copy_tags_from_user(maddr, tags,
> +							   num_tags);
> +			kvm_release_pfn_dirty(pfn);
> +		}
> +

Is it actually safe to do this without holding any lock, without
checking anything against the mmu_notifier_seq? What if the pages are
being swapped out? Or the memslot removed from under your feet?

It looks... dangerous. Do you even want to allow this while vcpus are
actually running?

> +		if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
> +			return -EFAULT;
> +
> +		gfn++;
> +		tags += num_tags;
> +		length -= PAGE_SIZE;
> +	}
> +
> +	return 0;
> +}
> +
>  long kvm_arch_vm_ioctl(struct file *filp,
>  		       unsigned int ioctl, unsigned long arg)
>  {
> @@ -1333,6 +1380,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
>  
>  		return 0;
>  	}
> +	case KVM_ARM_MTE_COPY_TAGS: {
> +		struct kvm_arm_copy_mte_tags copy_tags;
> +
> +		if (!kvm_has_mte(kvm))
> +			return -EINVAL;
> +
> +		if (copy_from_user(&copy_tags, argp, sizeof(copy_tags)))
> +			return -EFAULT;
> +		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
> +	}
>  	default:
>  		return -EINVAL;
>  	}
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 05618a4abf7e..b75af0f9ba55 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1423,6 +1423,7 @@ struct kvm_s390_ucas_mapping {
>  /* Available with KVM_CAP_PMU_EVENT_FILTER */
>  #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
>  #define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
> +#define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
>  
>  /* ioctl for vm fd */
>  #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
> -- 
> 2.20.1
> 
> 

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

Re: [PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest

[Marc Zyngier]

On Mon, 01 Mar 2021 14:23:14 +0000,
Steven Price <steven.price@arm.com> wrote:
> 
> The VMM may not wish to have it's own mapping of guest memory mapped
> with PROT_MTE because this causes problems if the VMM has tag checking
> enabled (the guest controls the tags in physical RAM and it's unlikely
> the tags are correct for the VMM).
> 
> Instead add a new ioctl which allows the VMM to easily read/write the
> tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
> while the VMM can still read/write the tags for the purpose of
> migration.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/uapi/asm/kvm.h | 13 +++++++
>  arch/arm64/kvm/arm.c              | 57 +++++++++++++++++++++++++++++++
>  include/uapi/linux/kvm.h          |  1 +
>  3 files changed, 71 insertions(+)
> 
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 24223adae150..5fc2534ac5df 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -184,6 +184,19 @@ struct kvm_vcpu_events {
>  	__u32 reserved[12];
>  };
>  
> +struct kvm_arm_copy_mte_tags {
> +	__u64 guest_ipa;
> +	__u64 length;
> +	union {
> +		void __user *addr;
> +		__u64 padding;
> +	};
> +	__u64 flags;

I'd be keen on a couple of reserved __64s. Just in case...

> +};
> +
> +#define KVM_ARM_TAGS_TO_GUEST		0
> +#define KVM_ARM_TAGS_FROM_GUEST		1
> +
>  /* If you need to interpret the index values, here is the key: */
>  #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
>  #define KVM_REG_ARM_COPROC_SHIFT	16
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 46bf319f6cb7..01d404833e24 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1297,6 +1297,53 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
>  	}
>  }
>  
> +static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
> +				      struct kvm_arm_copy_mte_tags *copy_tags)
> +{
> +	gpa_t guest_ipa = copy_tags->guest_ipa;
> +	size_t length = copy_tags->length;
> +	void __user *tags = copy_tags->addr;
> +	gpa_t gfn;
> +	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
> +
> +	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
> +		return -EINVAL;
> +
> +	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
> +		return -EINVAL;

It is a bit odd to require userspace to provide a page-aligned
addr/size, as it now has to find out about the kernel's page
size. MTE_GRANULE_SIZE-aligned values would make more sense. Is there
an underlying reason for this?

> +
> +	gfn = gpa_to_gfn(guest_ipa);
> +
> +	while (length > 0) {
> +		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
> +		void *maddr;
> +		unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
> +
> +		if (is_error_noslot_pfn(pfn))
> +			return -ENOENT;
> +
> +		maddr = page_address(pfn_to_page(pfn));
> +
> +		if (!write) {
> +			num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
> +			kvm_release_pfn_clean(pfn);
> +		} else {
> +			num_tags = mte_copy_tags_from_user(maddr, tags,
> +							   num_tags);
> +			kvm_release_pfn_dirty(pfn);
> +		}
> +

Is it actually safe to do this without holding any lock, without
checking anything against the mmu_notifier_seq? What if the pages are
being swapped out? Or the memslot removed from under your feet?

It looks... dangerous. Do you even want to allow this while vcpus are
actually running?

> +		if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
> +			return -EFAULT;
> +
> +		gfn++;
> +		tags += num_tags;
> +		length -= PAGE_SIZE;
> +	}
> +
> +	return 0;
> +}
> +
>  long kvm_arch_vm_ioctl(struct file *filp,
>  		       unsigned int ioctl, unsigned long arg)
>  {
> @@ -1333,6 +1380,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
>  
>  		return 0;
>  	}
> +	case KVM_ARM_MTE_COPY_TAGS: {
> +		struct kvm_arm_copy_mte_tags copy_tags;
> +
> +		if (!kvm_has_mte(kvm))
> +			return -EINVAL;
> +
> +		if (copy_from_user(&copy_tags, argp, sizeof(copy_tags)))
> +			return -EFAULT;
> +		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
> +	}
>  	default:
>  		return -EINVAL;
>  	}
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 05618a4abf7e..b75af0f9ba55 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1423,6 +1423,7 @@ struct kvm_s390_ucas_mapping {
>  /* Available with KVM_CAP_PMU_EVENT_FILTER */
>  #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
>  #define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
> +#define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
>  
>  /* ioctl for vm fd */
>  #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
> -- 
> 2.20.1
> 
> 

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest

[Marc Zyngier]

On Mon, 01 Mar 2021 14:23:14 +0000,
Steven Price <steven.price@arm.com> wrote:
> 
> The VMM may not wish to have it's own mapping of guest memory mapped
> with PROT_MTE because this causes problems if the VMM has tag checking
> enabled (the guest controls the tags in physical RAM and it's unlikely
> the tags are correct for the VMM).
> 
> Instead add a new ioctl which allows the VMM to easily read/write the
> tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
> while the VMM can still read/write the tags for the purpose of
> migration.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/uapi/asm/kvm.h | 13 +++++++
>  arch/arm64/kvm/arm.c              | 57 +++++++++++++++++++++++++++++++
>  include/uapi/linux/kvm.h          |  1 +
>  3 files changed, 71 insertions(+)
> 
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 24223adae150..5fc2534ac5df 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -184,6 +184,19 @@ struct kvm_vcpu_events {
>  	__u32 reserved[12];
>  };
>  
> +struct kvm_arm_copy_mte_tags {
> +	__u64 guest_ipa;
> +	__u64 length;
> +	union {
> +		void __user *addr;
> +		__u64 padding;
> +	};
> +	__u64 flags;

I'd be keen on a couple of reserved __64s. Just in case...

> +};
> +
> +#define KVM_ARM_TAGS_TO_GUEST		0
> +#define KVM_ARM_TAGS_FROM_GUEST		1
> +
>  /* If you need to interpret the index values, here is the key: */
>  #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
>  #define KVM_REG_ARM_COPROC_SHIFT	16
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 46bf319f6cb7..01d404833e24 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1297,6 +1297,53 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
>  	}
>  }
>  
> +static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
> +				      struct kvm_arm_copy_mte_tags *copy_tags)
> +{
> +	gpa_t guest_ipa = copy_tags->guest_ipa;
> +	size_t length = copy_tags->length;
> +	void __user *tags = copy_tags->addr;
> +	gpa_t gfn;
> +	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
> +
> +	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
> +		return -EINVAL;
> +
> +	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
> +		return -EINVAL;

It is a bit odd to require userspace to provide a page-aligned
addr/size, as it now has to find out about the kernel's page
size. MTE_GRANULE_SIZE-aligned values would make more sense. Is there
an underlying reason for this?

> +
> +	gfn = gpa_to_gfn(guest_ipa);
> +
> +	while (length > 0) {
> +		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
> +		void *maddr;
> +		unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
> +
> +		if (is_error_noslot_pfn(pfn))
> +			return -ENOENT;
> +
> +		maddr = page_address(pfn_to_page(pfn));
> +
> +		if (!write) {
> +			num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
> +			kvm_release_pfn_clean(pfn);
> +		} else {
> +			num_tags = mte_copy_tags_from_user(maddr, tags,
> +							   num_tags);
> +			kvm_release_pfn_dirty(pfn);
> +		}
> +

Is it actually safe to do this without holding any lock, without
checking anything against the mmu_notifier_seq? What if the pages are
being swapped out? Or the memslot removed from under your feet?

It looks... dangerous. Do you even want to allow this while vcpus are
actually running?

> +		if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
> +			return -EFAULT;
> +
> +		gfn++;
> +		tags += num_tags;
> +		length -= PAGE_SIZE;
> +	}
> +
> +	return 0;
> +}
> +
>  long kvm_arch_vm_ioctl(struct file *filp,
>  		       unsigned int ioctl, unsigned long arg)
>  {
> @@ -1333,6 +1380,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
>  
>  		return 0;
>  	}
> +	case KVM_ARM_MTE_COPY_TAGS: {
> +		struct kvm_arm_copy_mte_tags copy_tags;
> +
> +		if (!kvm_has_mte(kvm))
> +			return -EINVAL;
> +
> +		if (copy_from_user(&copy_tags, argp, sizeof(copy_tags)))
> +			return -EFAULT;
> +		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
> +	}
>  	default:
>  		return -EINVAL;
>  	}
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 05618a4abf7e..b75af0f9ba55 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1423,6 +1423,7 @@ struct kvm_s390_ucas_mapping {
>  /* Available with KVM_CAP_PMU_EVENT_FILTER */
>  #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
>  #define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
> +#define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
>  
>  /* ioctl for vm fd */
>  #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
> -- 
> 2.20.1
> 
> 

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.
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kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

Re: [PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest

[Marc Zyngier]

On Mon, 01 Mar 2021 14:23:14 +0000,
Steven Price <steven.price@arm.com> wrote:
> 
> The VMM may not wish to have it's own mapping of guest memory mapped
> with PROT_MTE because this causes problems if the VMM has tag checking
> enabled (the guest controls the tags in physical RAM and it's unlikely
> the tags are correct for the VMM).
> 
> Instead add a new ioctl which allows the VMM to easily read/write the
> tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
> while the VMM can still read/write the tags for the purpose of
> migration.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/uapi/asm/kvm.h | 13 +++++++
>  arch/arm64/kvm/arm.c              | 57 +++++++++++++++++++++++++++++++
>  include/uapi/linux/kvm.h          |  1 +
>  3 files changed, 71 insertions(+)
> 
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 24223adae150..5fc2534ac5df 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -184,6 +184,19 @@ struct kvm_vcpu_events {
>  	__u32 reserved[12];
>  };
>  
> +struct kvm_arm_copy_mte_tags {
> +	__u64 guest_ipa;
> +	__u64 length;
> +	union {
> +		void __user *addr;
> +		__u64 padding;
> +	};
> +	__u64 flags;

I'd be keen on a couple of reserved __64s. Just in case...

> +};
> +
> +#define KVM_ARM_TAGS_TO_GUEST		0
> +#define KVM_ARM_TAGS_FROM_GUEST		1
> +
>  /* If you need to interpret the index values, here is the key: */
>  #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
>  #define KVM_REG_ARM_COPROC_SHIFT	16
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 46bf319f6cb7..01d404833e24 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1297,6 +1297,53 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
>  	}
>  }
>  
> +static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
> +				      struct kvm_arm_copy_mte_tags *copy_tags)
> +{
> +	gpa_t guest_ipa = copy_tags->guest_ipa;
> +	size_t length = copy_tags->length;
> +	void __user *tags = copy_tags->addr;
> +	gpa_t gfn;
> +	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
> +
> +	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
> +		return -EINVAL;
> +
> +	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
> +		return -EINVAL;

It is a bit odd to require userspace to provide a page-aligned
addr/size, as it now has to find out about the kernel's page
size. MTE_GRANULE_SIZE-aligned values would make more sense. Is there
an underlying reason for this?

> +
> +	gfn = gpa_to_gfn(guest_ipa);
> +
> +	while (length > 0) {
> +		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
> +		void *maddr;
> +		unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
> +
> +		if (is_error_noslot_pfn(pfn))
> +			return -ENOENT;
> +
> +		maddr = page_address(pfn_to_page(pfn));
> +
> +		if (!write) {
> +			num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
> +			kvm_release_pfn_clean(pfn);
> +		} else {
> +			num_tags = mte_copy_tags_from_user(maddr, tags,
> +							   num_tags);
> +			kvm_release_pfn_dirty(pfn);
> +		}
> +

Is it actually safe to do this without holding any lock, without
checking anything against the mmu_notifier_seq? What if the pages are
being swapped out? Or the memslot removed from under your feet?

It looks... dangerous. Do you even want to allow this while vcpus are
actually running?

> +		if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
> +			return -EFAULT;
> +
> +		gfn++;
> +		tags += num_tags;
> +		length -= PAGE_SIZE;
> +	}
> +
> +	return 0;
> +}
> +
>  long kvm_arch_vm_ioctl(struct file *filp,
>  		       unsigned int ioctl, unsigned long arg)
>  {
> @@ -1333,6 +1380,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
>  
>  		return 0;
>  	}
> +	case KVM_ARM_MTE_COPY_TAGS: {
> +		struct kvm_arm_copy_mte_tags copy_tags;
> +
> +		if (!kvm_has_mte(kvm))
> +			return -EINVAL;
> +
> +		if (copy_from_user(&copy_tags, argp, sizeof(copy_tags)))
> +			return -EFAULT;
> +		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
> +	}
>  	default:
>  		return -EINVAL;
>  	}
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 05618a4abf7e..b75af0f9ba55 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1423,6 +1423,7 @@ struct kvm_s390_ucas_mapping {
>  /* Available with KVM_CAP_PMU_EVENT_FILTER */
>  #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
>  #define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
> +#define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
>  
>  /* ioctl for vm fd */
>  #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
> -- 
> 2.20.1
> 
> 

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

Re: [PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest

[Steven Price]

On 09/03/2021 17:57, Marc Zyngier wrote:
> On Mon, 01 Mar 2021 14:23:14 +0000,
> Steven Price <steven.price@arm.com> wrote:
>>
>> The VMM may not wish to have it's own mapping of guest memory mapped
>> with PROT_MTE because this causes problems if the VMM has tag checking
>> enabled (the guest controls the tags in physical RAM and it's unlikely
>> the tags are correct for the VMM).
>>
>> Instead add a new ioctl which allows the VMM to easily read/write the
>> tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
>> while the VMM can still read/write the tags for the purpose of
>> migration.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/uapi/asm/kvm.h | 13 +++++++
>>   arch/arm64/kvm/arm.c              | 57 +++++++++++++++++++++++++++++++
>>   include/uapi/linux/kvm.h          |  1 +
>>   3 files changed, 71 insertions(+)
>>
>> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
>> index 24223adae150..5fc2534ac5df 100644
>> --- a/arch/arm64/include/uapi/asm/kvm.h
>> +++ b/arch/arm64/include/uapi/asm/kvm.h
>> @@ -184,6 +184,19 @@ struct kvm_vcpu_events {
>>   	__u32 reserved[12];
>>   };
>>   
>> +struct kvm_arm_copy_mte_tags {
>> +	__u64 guest_ipa;
>> +	__u64 length;
>> +	union {
>> +		void __user *addr;
>> +		__u64 padding;
>> +	};
>> +	__u64 flags;
> 
> I'd be keen on a couple of reserved __64s. Just in case...

Fair enough, I'll add a __u64 reserved[2];

>> +};
>> +
>> +#define KVM_ARM_TAGS_TO_GUEST		0
>> +#define KVM_ARM_TAGS_FROM_GUEST		1
>> +
>>   /* If you need to interpret the index values, here is the key: */
>>   #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
>>   #define KVM_REG_ARM_COPROC_SHIFT	16
>> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
>> index 46bf319f6cb7..01d404833e24 100644
>> --- a/arch/arm64/kvm/arm.c
>> +++ b/arch/arm64/kvm/arm.c
>> @@ -1297,6 +1297,53 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
>>   	}
>>   }
>>   
>> +static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
>> +				      struct kvm_arm_copy_mte_tags *copy_tags)
>> +{
>> +	gpa_t guest_ipa = copy_tags->guest_ipa;
>> +	size_t length = copy_tags->length;
>> +	void __user *tags = copy_tags->addr;
>> +	gpa_t gfn;
>> +	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
>> +
>> +	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
>> +		return -EINVAL;
>> +
>> +	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
>> +		return -EINVAL;
> 
> It is a bit odd to require userspace to provide a page-aligned
> addr/size, as it now has to find out about the kernel's page
> size. MTE_GRANULE_SIZE-aligned values would make more sense. Is there
> an underlying reason for this?

No fundamental reason, my thoughts were:

  * It's likely user space is naturally going to be using page-aligned 
quantities during migration, so it already has to care about this.

  * It makes the loop below easier.

  * It's easy to relax the restriction in the future if it becomes a 
problem, much harder to tighten it without breaking anything.

But I can switch to MTE_GRANULE_SIZE if you'd prefer, let me know.

>> +
>> +	gfn = gpa_to_gfn(guest_ipa);
>> +
>> +	while (length > 0) {
>> +		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
>> +		void *maddr;
>> +		unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
>> +
>> +		if (is_error_noslot_pfn(pfn))
>> +			return -ENOENT;
>> +
>> +		maddr = page_address(pfn_to_page(pfn));
>> +
>> +		if (!write) {
>> +			num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
>> +			kvm_release_pfn_clean(pfn);
>> +		} else {
>> +			num_tags = mte_copy_tags_from_user(maddr, tags,
>> +							   num_tags);
>> +			kvm_release_pfn_dirty(pfn);
>> +		}
>> +
> 
> Is it actually safe to do this without holding any lock, without
> checking anything against the mmu_notifier_seq? What if the pages are
> being swapped out? Or the memslot removed from under your feet?
> 
> It looks... dangerous. Do you even want to allow this while vcpus are
> actually running?

Umm... yeah I'm not sure how I managed to forgot the locks. This should 
be holding kvm->slots_lock to prevent the slot going under our feet. I 
was surprised that lockdep didn't catch that, until I noticed I'd 
disabled it and discovered why (the model makes it incredibly slow). 
However I've done a run with it enabled now - and with the 
kvm->slots_lock taken it's happy.

gfn_to_pfn_prot() internally calls a variant of get_user_pages() - so 
swapping out shouldn't be a problem.

In terms of running with the vcpus running - given this is going to be 
used for migration I think that's pretty much a requirement. We want to 
be able to dump the tags while executing to enable early transfer of the 
memory.

Steve

>> +		if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
>> +			return -EFAULT;
>> +
>> +		gfn++;
>> +		tags += num_tags;
>> +		length -= PAGE_SIZE;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>   long kvm_arch_vm_ioctl(struct file *filp,
>>   		       unsigned int ioctl, unsigned long arg)
>>   {
>> @@ -1333,6 +1380,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
>>   
>>   		return 0;
>>   	}
>> +	case KVM_ARM_MTE_COPY_TAGS: {
>> +		struct kvm_arm_copy_mte_tags copy_tags;
>> +
>> +		if (!kvm_has_mte(kvm))
>> +			return -EINVAL;
>> +
>> +		if (copy_from_user(&copy_tags, argp, sizeof(copy_tags)))
>> +			return -EFAULT;
>> +		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
>> +	}
>>   	default:
>>   		return -EINVAL;
>>   	}
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 05618a4abf7e..b75af0f9ba55 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1423,6 +1423,7 @@ struct kvm_s390_ucas_mapping {
>>   /* Available with KVM_CAP_PMU_EVENT_FILTER */
>>   #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
>>   #define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
>> +#define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
>>   
>>   /* ioctl for vm fd */
>>   #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
>> -- 
>> 2.20.1
>>
>>
> 
> Thanks,
> 
> 	M.
> 

Re: [PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest

[Steven Price]

On 09/03/2021 17:57, Marc Zyngier wrote:
> On Mon, 01 Mar 2021 14:23:14 +0000,
> Steven Price <steven.price@arm.com> wrote:
>>
>> The VMM may not wish to have it's own mapping of guest memory mapped
>> with PROT_MTE because this causes problems if the VMM has tag checking
>> enabled (the guest controls the tags in physical RAM and it's unlikely
>> the tags are correct for the VMM).
>>
>> Instead add a new ioctl which allows the VMM to easily read/write the
>> tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
>> while the VMM can still read/write the tags for the purpose of
>> migration.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/uapi/asm/kvm.h | 13 +++++++
>>   arch/arm64/kvm/arm.c              | 57 +++++++++++++++++++++++++++++++
>>   include/uapi/linux/kvm.h          |  1 +
>>   3 files changed, 71 insertions(+)
>>
>> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
>> index 24223adae150..5fc2534ac5df 100644
>> --- a/arch/arm64/include/uapi/asm/kvm.h
>> +++ b/arch/arm64/include/uapi/asm/kvm.h
>> @@ -184,6 +184,19 @@ struct kvm_vcpu_events {
>>   	__u32 reserved[12];
>>   };
>>   
>> +struct kvm_arm_copy_mte_tags {
>> +	__u64 guest_ipa;
>> +	__u64 length;
>> +	union {
>> +		void __user *addr;
>> +		__u64 padding;
>> +	};
>> +	__u64 flags;
> 
> I'd be keen on a couple of reserved __64s. Just in case...

Fair enough, I'll add a __u64 reserved[2];

>> +};
>> +
>> +#define KVM_ARM_TAGS_TO_GUEST		0
>> +#define KVM_ARM_TAGS_FROM_GUEST		1
>> +
>>   /* If you need to interpret the index values, here is the key: */
>>   #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
>>   #define KVM_REG_ARM_COPROC_SHIFT	16
>> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
>> index 46bf319f6cb7..01d404833e24 100644
>> --- a/arch/arm64/kvm/arm.c
>> +++ b/arch/arm64/kvm/arm.c
>> @@ -1297,6 +1297,53 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
>>   	}
>>   }
>>   
>> +static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
>> +				      struct kvm_arm_copy_mte_tags *copy_tags)
>> +{
>> +	gpa_t guest_ipa = copy_tags->guest_ipa;
>> +	size_t length = copy_tags->length;
>> +	void __user *tags = copy_tags->addr;
>> +	gpa_t gfn;
>> +	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
>> +
>> +	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
>> +		return -EINVAL;
>> +
>> +	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
>> +		return -EINVAL;
> 
> It is a bit odd to require userspace to provide a page-aligned
> addr/size, as it now has to find out about the kernel's page
> size. MTE_GRANULE_SIZE-aligned values would make more sense. Is there
> an underlying reason for this?

No fundamental reason, my thoughts were:

  * It's likely user space is naturally going to be using page-aligned 
quantities during migration, so it already has to care about this.

  * It makes the loop below easier.

  * It's easy to relax the restriction in the future if it becomes a 
problem, much harder to tighten it without breaking anything.

But I can switch to MTE_GRANULE_SIZE if you'd prefer, let me know.

>> +
>> +	gfn = gpa_to_gfn(guest_ipa);
>> +
>> +	while (length > 0) {
>> +		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
>> +		void *maddr;
>> +		unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
>> +
>> +		if (is_error_noslot_pfn(pfn))
>> +			return -ENOENT;
>> +
>> +		maddr = page_address(pfn_to_page(pfn));
>> +
>> +		if (!write) {
>> +			num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
>> +			kvm_release_pfn_clean(pfn);
>> +		} else {
>> +			num_tags = mte_copy_tags_from_user(maddr, tags,
>> +							   num_tags);
>> +			kvm_release_pfn_dirty(pfn);
>> +		}
>> +
> 
> Is it actually safe to do this without holding any lock, without
> checking anything against the mmu_notifier_seq? What if the pages are
> being swapped out? Or the memslot removed from under your feet?
> 
> It looks... dangerous. Do you even want to allow this while vcpus are
> actually running?

Umm... yeah I'm not sure how I managed to forgot the locks. This should 
be holding kvm->slots_lock to prevent the slot going under our feet. I 
was surprised that lockdep didn't catch that, until I noticed I'd 
disabled it and discovered why (the model makes it incredibly slow). 
However I've done a run with it enabled now - and with the 
kvm->slots_lock taken it's happy.

gfn_to_pfn_prot() internally calls a variant of get_user_pages() - so 
swapping out shouldn't be a problem.

In terms of running with the vcpus running - given this is going to be 
used for migration I think that's pretty much a requirement. We want to 
be able to dump the tags while executing to enable early transfer of the 
memory.

Steve

>> +		if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
>> +			return -EFAULT;
>> +
>> +		gfn++;
>> +		tags += num_tags;
>> +		length -= PAGE_SIZE;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>   long kvm_arch_vm_ioctl(struct file *filp,
>>   		       unsigned int ioctl, unsigned long arg)
>>   {
>> @@ -1333,6 +1380,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
>>   
>>   		return 0;
>>   	}
>> +	case KVM_ARM_MTE_COPY_TAGS: {
>> +		struct kvm_arm_copy_mte_tags copy_tags;
>> +
>> +		if (!kvm_has_mte(kvm))
>> +			return -EINVAL;
>> +
>> +		if (copy_from_user(&copy_tags, argp, sizeof(copy_tags)))
>> +			return -EFAULT;
>> +		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
>> +	}
>>   	default:
>>   		return -EINVAL;
>>   	}
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 05618a4abf7e..b75af0f9ba55 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1423,6 +1423,7 @@ struct kvm_s390_ucas_mapping {
>>   /* Available with KVM_CAP_PMU_EVENT_FILTER */
>>   #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
>>   #define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
>> +#define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
>>   
>>   /* ioctl for vm fd */
>>   #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
>> -- 
>> 2.20.1
>>
>>
> 
> Thanks,
> 
> 	M.
> 


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest

[Steven Price]

On 09/03/2021 17:57, Marc Zyngier wrote:
> On Mon, 01 Mar 2021 14:23:14 +0000,
> Steven Price <steven.price@arm.com> wrote:
>>
>> The VMM may not wish to have it's own mapping of guest memory mapped
>> with PROT_MTE because this causes problems if the VMM has tag checking
>> enabled (the guest controls the tags in physical RAM and it's unlikely
>> the tags are correct for the VMM).
>>
>> Instead add a new ioctl which allows the VMM to easily read/write the
>> tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
>> while the VMM can still read/write the tags for the purpose of
>> migration.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/uapi/asm/kvm.h | 13 +++++++
>>   arch/arm64/kvm/arm.c              | 57 +++++++++++++++++++++++++++++++
>>   include/uapi/linux/kvm.h          |  1 +
>>   3 files changed, 71 insertions(+)
>>
>> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
>> index 24223adae150..5fc2534ac5df 100644
>> --- a/arch/arm64/include/uapi/asm/kvm.h
>> +++ b/arch/arm64/include/uapi/asm/kvm.h
>> @@ -184,6 +184,19 @@ struct kvm_vcpu_events {
>>   	__u32 reserved[12];
>>   };
>>   
>> +struct kvm_arm_copy_mte_tags {
>> +	__u64 guest_ipa;
>> +	__u64 length;
>> +	union {
>> +		void __user *addr;
>> +		__u64 padding;
>> +	};
>> +	__u64 flags;
> 
> I'd be keen on a couple of reserved __64s. Just in case...

Fair enough, I'll add a __u64 reserved[2];

>> +};
>> +
>> +#define KVM_ARM_TAGS_TO_GUEST		0
>> +#define KVM_ARM_TAGS_FROM_GUEST		1
>> +
>>   /* If you need to interpret the index values, here is the key: */
>>   #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
>>   #define KVM_REG_ARM_COPROC_SHIFT	16
>> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
>> index 46bf319f6cb7..01d404833e24 100644
>> --- a/arch/arm64/kvm/arm.c
>> +++ b/arch/arm64/kvm/arm.c
>> @@ -1297,6 +1297,53 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
>>   	}
>>   }
>>   
>> +static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
>> +				      struct kvm_arm_copy_mte_tags *copy_tags)
>> +{
>> +	gpa_t guest_ipa = copy_tags->guest_ipa;
>> +	size_t length = copy_tags->length;
>> +	void __user *tags = copy_tags->addr;
>> +	gpa_t gfn;
>> +	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
>> +
>> +	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
>> +		return -EINVAL;
>> +
>> +	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
>> +		return -EINVAL;
> 
> It is a bit odd to require userspace to provide a page-aligned
> addr/size, as it now has to find out about the kernel's page
> size. MTE_GRANULE_SIZE-aligned values would make more sense. Is there
> an underlying reason for this?

No fundamental reason, my thoughts were:

  * It's likely user space is naturally going to be using page-aligned 
quantities during migration, so it already has to care about this.

  * It makes the loop below easier.

  * It's easy to relax the restriction in the future if it becomes a 
problem, much harder to tighten it without breaking anything.

But I can switch to MTE_GRANULE_SIZE if you'd prefer, let me know.

>> +
>> +	gfn = gpa_to_gfn(guest_ipa);
>> +
>> +	while (length > 0) {
>> +		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
>> +		void *maddr;
>> +		unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
>> +
>> +		if (is_error_noslot_pfn(pfn))
>> +			return -ENOENT;
>> +
>> +		maddr = page_address(pfn_to_page(pfn));
>> +
>> +		if (!write) {
>> +			num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
>> +			kvm_release_pfn_clean(pfn);
>> +		} else {
>> +			num_tags = mte_copy_tags_from_user(maddr, tags,
>> +							   num_tags);
>> +			kvm_release_pfn_dirty(pfn);
>> +		}
>> +
> 
> Is it actually safe to do this without holding any lock, without
> checking anything against the mmu_notifier_seq? What if the pages are
> being swapped out? Or the memslot removed from under your feet?
> 
> It looks... dangerous. Do you even want to allow this while vcpus are
> actually running?

Umm... yeah I'm not sure how I managed to forgot the locks. This should 
be holding kvm->slots_lock to prevent the slot going under our feet. I 
was surprised that lockdep didn't catch that, until I noticed I'd 
disabled it and discovered why (the model makes it incredibly slow). 
However I've done a run with it enabled now - and with the 
kvm->slots_lock taken it's happy.

gfn_to_pfn_prot() internally calls a variant of get_user_pages() - so 
swapping out shouldn't be a problem.

In terms of running with the vcpus running - given this is going to be 
used for migration I think that's pretty much a requirement. We want to 
be able to dump the tags while executing to enable early transfer of the 
memory.

Steve

>> +		if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
>> +			return -EFAULT;
>> +
>> +		gfn++;
>> +		tags += num_tags;
>> +		length -= PAGE_SIZE;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>   long kvm_arch_vm_ioctl(struct file *filp,
>>   		       unsigned int ioctl, unsigned long arg)
>>   {
>> @@ -1333,6 +1380,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
>>   
>>   		return 0;
>>   	}
>> +	case KVM_ARM_MTE_COPY_TAGS: {
>> +		struct kvm_arm_copy_mte_tags copy_tags;
>> +
>> +		if (!kvm_has_mte(kvm))
>> +			return -EINVAL;
>> +
>> +		if (copy_from_user(&copy_tags, argp, sizeof(copy_tags)))
>> +			return -EFAULT;
>> +		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
>> +	}
>>   	default:
>>   		return -EINVAL;
>>   	}
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 05618a4abf7e..b75af0f9ba55 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1423,6 +1423,7 @@ struct kvm_s390_ucas_mapping {
>>   /* Available with KVM_CAP_PMU_EVENT_FILTER */
>>   #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
>>   #define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
>> +#define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
>>   
>>   /* ioctl for vm fd */
>>   #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
>> -- 
>> 2.20.1
>>
>>
> 
> Thanks,
> 
> 	M.
> 

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

Re: [PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest

[Steven Price]

On 09/03/2021 17:57, Marc Zyngier wrote:
> On Mon, 01 Mar 2021 14:23:14 +0000,
> Steven Price <steven.price@arm.com> wrote:
>>
>> The VMM may not wish to have it's own mapping of guest memory mapped
>> with PROT_MTE because this causes problems if the VMM has tag checking
>> enabled (the guest controls the tags in physical RAM and it's unlikely
>> the tags are correct for the VMM).
>>
>> Instead add a new ioctl which allows the VMM to easily read/write the
>> tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
>> while the VMM can still read/write the tags for the purpose of
>> migration.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   arch/arm64/include/uapi/asm/kvm.h | 13 +++++++
>>   arch/arm64/kvm/arm.c              | 57 +++++++++++++++++++++++++++++++
>>   include/uapi/linux/kvm.h          |  1 +
>>   3 files changed, 71 insertions(+)
>>
>> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
>> index 24223adae150..5fc2534ac5df 100644
>> --- a/arch/arm64/include/uapi/asm/kvm.h
>> +++ b/arch/arm64/include/uapi/asm/kvm.h
>> @@ -184,6 +184,19 @@ struct kvm_vcpu_events {
>>   	__u32 reserved[12];
>>   };
>>   
>> +struct kvm_arm_copy_mte_tags {
>> +	__u64 guest_ipa;
>> +	__u64 length;
>> +	union {
>> +		void __user *addr;
>> +		__u64 padding;
>> +	};
>> +	__u64 flags;
> 
> I'd be keen on a couple of reserved __64s. Just in case...

Fair enough, I'll add a __u64 reserved[2];

>> +};
>> +
>> +#define KVM_ARM_TAGS_TO_GUEST		0
>> +#define KVM_ARM_TAGS_FROM_GUEST		1
>> +
>>   /* If you need to interpret the index values, here is the key: */
>>   #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
>>   #define KVM_REG_ARM_COPROC_SHIFT	16
>> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
>> index 46bf319f6cb7..01d404833e24 100644
>> --- a/arch/arm64/kvm/arm.c
>> +++ b/arch/arm64/kvm/arm.c
>> @@ -1297,6 +1297,53 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
>>   	}
>>   }
>>   
>> +static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
>> +				      struct kvm_arm_copy_mte_tags *copy_tags)
>> +{
>> +	gpa_t guest_ipa = copy_tags->guest_ipa;
>> +	size_t length = copy_tags->length;
>> +	void __user *tags = copy_tags->addr;
>> +	gpa_t gfn;
>> +	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
>> +
>> +	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
>> +		return -EINVAL;
>> +
>> +	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
>> +		return -EINVAL;
> 
> It is a bit odd to require userspace to provide a page-aligned
> addr/size, as it now has to find out about the kernel's page
> size. MTE_GRANULE_SIZE-aligned values would make more sense. Is there
> an underlying reason for this?

No fundamental reason, my thoughts were:

  * It's likely user space is naturally going to be using page-aligned 
quantities during migration, so it already has to care about this.

  * It makes the loop below easier.

  * It's easy to relax the restriction in the future if it becomes a 
problem, much harder to tighten it without breaking anything.

But I can switch to MTE_GRANULE_SIZE if you'd prefer, let me know.

>> +
>> +	gfn = gpa_to_gfn(guest_ipa);
>> +
>> +	while (length > 0) {
>> +		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
>> +		void *maddr;
>> +		unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
>> +
>> +		if (is_error_noslot_pfn(pfn))
>> +			return -ENOENT;
>> +
>> +		maddr = page_address(pfn_to_page(pfn));
>> +
>> +		if (!write) {
>> +			num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
>> +			kvm_release_pfn_clean(pfn);
>> +		} else {
>> +			num_tags = mte_copy_tags_from_user(maddr, tags,
>> +							   num_tags);
>> +			kvm_release_pfn_dirty(pfn);
>> +		}
>> +
> 
> Is it actually safe to do this without holding any lock, without
> checking anything against the mmu_notifier_seq? What if the pages are
> being swapped out? Or the memslot removed from under your feet?
> 
> It looks... dangerous. Do you even want to allow this while vcpus are
> actually running?

Umm... yeah I'm not sure how I managed to forgot the locks. This should 
be holding kvm->slots_lock to prevent the slot going under our feet. I 
was surprised that lockdep didn't catch that, until I noticed I'd 
disabled it and discovered why (the model makes it incredibly slow). 
However I've done a run with it enabled now - and with the 
kvm->slots_lock taken it's happy.

gfn_to_pfn_prot() internally calls a variant of get_user_pages() - so 
swapping out shouldn't be a problem.

In terms of running with the vcpus running - given this is going to be 
used for migration I think that's pretty much a requirement. We want to 
be able to dump the tags while executing to enable early transfer of the 
memory.

Steve

>> +		if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
>> +			return -EFAULT;
>> +
>> +		gfn++;
>> +		tags += num_tags;
>> +		length -= PAGE_SIZE;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>   long kvm_arch_vm_ioctl(struct file *filp,
>>   		       unsigned int ioctl, unsigned long arg)
>>   {
>> @@ -1333,6 +1380,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
>>   
>>   		return 0;
>>   	}
>> +	case KVM_ARM_MTE_COPY_TAGS: {
>> +		struct kvm_arm_copy_mte_tags copy_tags;
>> +
>> +		if (!kvm_has_mte(kvm))
>> +			return -EINVAL;
>> +
>> +		if (copy_from_user(&copy_tags, argp, sizeof(copy_tags)))
>> +			return -EFAULT;
>> +		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
>> +	}
>>   	default:
>>   		return -EINVAL;
>>   	}
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 05618a4abf7e..b75af0f9ba55 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1423,6 +1423,7 @@ struct kvm_s390_ucas_mapping {
>>   /* Available with KVM_CAP_PMU_EVENT_FILTER */
>>   #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
>>   #define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
>> +#define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
>>   
>>   /* ioctl for vm fd */
>>   #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
>> -- 
>> 2.20.1
>>
>>
> 
> Thanks,
> 
> 	M.
> 

[PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl

[Steven Price]

A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports
granting a guest access to the tags, and provides a mechanism for the
VMM to enable it.

A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to
access the tags of a guest without having to maintain a PROT_MTE mapping
in userspace. The above capability gates access to the ioctl.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index aed52b0fc16e..1406ea138127 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
 Allows Xen vCPU attributes to be read. For the structure and types,
 see KVM_XEN_VCPU_SET_ATTR above.
 
+4.131 KVM_ARM_MTE_COPY_TAGS
+---------------------------
+
+:Capability: KVM_CAP_ARM_MTE
+:Architectures: arm64
+:Type: vm ioctl
+:Parameters: struct kvm_arm_copy_mte_tags
+:Returns: 0 on success, < 0 on error
+
+Copies Memory Tagging Extension (MTE) tags to/from guest tag memory. The
+starting address and length of guest memory must be ``PAGE_SIZE`` aligned.
+
+The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)``
+bytes (i.e. 1/16th of the corresponding size). Each byte contains a single tag
+value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
+``PTRACE_POKEMTETAGS``.
+
 5. The kvm_run structure
 ========================
 
@@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
 This capability can be used to check / enable 2nd DAWR feature provided
 by POWER10 processor.
 
+7.23 KVM_CAP_ARM_MTE
+--------------------
+
+:Architectures: arm64
+:Parameters: none
+
+This capability indicates that KVM (and the hardware) supports exposing the
+Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the
+VMM before the guest will be granted access.
+
+When enabled the guest is able to access tags associated with any memory given
+to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so
+that the tags are maintained during swap or hibernation of the host, however
+the VMM needs to manually save/restore the tags as appropriate if the VM is
+migrated.
+
+When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
+perform a bulk copy of tags to/from the guest
+
 8. Other capabilities.
 ======================
 
@@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
 KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
 for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
 vcpu_info is set.
+
-- 
2.20.1

[PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl

[Steven Price]

A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports
granting a guest access to the tags, and provides a mechanism for the
VMM to enable it.

A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to
access the tags of a guest without having to maintain a PROT_MTE mapping
in userspace. The above capability gates access to the ioctl.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index aed52b0fc16e..1406ea138127 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
 Allows Xen vCPU attributes to be read. For the structure and types,
 see KVM_XEN_VCPU_SET_ATTR above.
 
+4.131 KVM_ARM_MTE_COPY_TAGS
+---------------------------
+
+:Capability: KVM_CAP_ARM_MTE
+:Architectures: arm64
+:Type: vm ioctl
+:Parameters: struct kvm_arm_copy_mte_tags
+:Returns: 0 on success, < 0 on error
+
+Copies Memory Tagging Extension (MTE) tags to/from guest tag memory. The
+starting address and length of guest memory must be ``PAGE_SIZE`` aligned.
+
+The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)``
+bytes (i.e. 1/16th of the corresponding size). Each byte contains a single tag
+value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
+``PTRACE_POKEMTETAGS``.
+
 5. The kvm_run structure
 ========================
 
@@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
 This capability can be used to check / enable 2nd DAWR feature provided
 by POWER10 processor.
 
+7.23 KVM_CAP_ARM_MTE
+--------------------
+
+:Architectures: arm64
+:Parameters: none
+
+This capability indicates that KVM (and the hardware) supports exposing the
+Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the
+VMM before the guest will be granted access.
+
+When enabled the guest is able to access tags associated with any memory given
+to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so
+that the tags are maintained during swap or hibernation of the host, however
+the VMM needs to manually save/restore the tags as appropriate if the VM is
+migrated.
+
+When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
+perform a bulk copy of tags to/from the guest
+
 8. Other capabilities.
 ======================
 
@@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
 KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
 for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
 vcpu_info is set.
+
-- 
2.20.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl

[Steven Price]

A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports
granting a guest access to the tags, and provides a mechanism for the
VMM to enable it.

A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to
access the tags of a guest without having to maintain a PROT_MTE mapping
in userspace. The above capability gates access to the ioctl.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index aed52b0fc16e..1406ea138127 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
 Allows Xen vCPU attributes to be read. For the structure and types,
 see KVM_XEN_VCPU_SET_ATTR above.
 
+4.131 KVM_ARM_MTE_COPY_TAGS
+---------------------------
+
+:Capability: KVM_CAP_ARM_MTE
+:Architectures: arm64
+:Type: vm ioctl
+:Parameters: struct kvm_arm_copy_mte_tags
+:Returns: 0 on success, < 0 on error
+
+Copies Memory Tagging Extension (MTE) tags to/from guest tag memory. The
+starting address and length of guest memory must be ``PAGE_SIZE`` aligned.
+
+The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)``
+bytes (i.e. 1/16th of the corresponding size). Each byte contains a single tag
+value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
+``PTRACE_POKEMTETAGS``.
+
 5. The kvm_run structure
 ========================
 
@@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
 This capability can be used to check / enable 2nd DAWR feature provided
 by POWER10 processor.
 
+7.23 KVM_CAP_ARM_MTE
+--------------------
+
+:Architectures: arm64
+:Parameters: none
+
+This capability indicates that KVM (and the hardware) supports exposing the
+Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the
+VMM before the guest will be granted access.
+
+When enabled the guest is able to access tags associated with any memory given
+to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so
+that the tags are maintained during swap or hibernation of the host, however
+the VMM needs to manually save/restore the tags as appropriate if the VM is
+migrated.
+
+When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
+perform a bulk copy of tags to/from the guest
+
 8. Other capabilities.
 ======================
 
@@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
 KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
 for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
 vcpu_info is set.
+
-- 
2.20.1

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

[PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl

[Steven Price]

A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports
granting a guest access to the tags, and provides a mechanism for the
VMM to enable it.

A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to
access the tags of a guest without having to maintain a PROT_MTE mapping
in userspace. The above capability gates access to the ioctl.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index aed52b0fc16e..1406ea138127 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
 Allows Xen vCPU attributes to be read. For the structure and types,
 see KVM_XEN_VCPU_SET_ATTR above.
 
+4.131 KVM_ARM_MTE_COPY_TAGS
+---------------------------
+
+:Capability: KVM_CAP_ARM_MTE
+:Architectures: arm64
+:Type: vm ioctl
+:Parameters: struct kvm_arm_copy_mte_tags
+:Returns: 0 on success, < 0 on error
+
+Copies Memory Tagging Extension (MTE) tags to/from guest tag memory. The
+starting address and length of guest memory must be ``PAGE_SIZE`` aligned.
+
+The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)``
+bytes (i.e. 1/16th of the corresponding size). Each byte contains a single tag
+value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
+``PTRACE_POKEMTETAGS``.
+
 5. The kvm_run structure
 ========================
 
@@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
 This capability can be used to check / enable 2nd DAWR feature provided
 by POWER10 processor.
 
+7.23 KVM_CAP_ARM_MTE
+--------------------
+
+:Architectures: arm64
+:Parameters: none
+
+This capability indicates that KVM (and the hardware) supports exposing the
+Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the
+VMM before the guest will be granted access.
+
+When enabled the guest is able to access tags associated with any memory given
+to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so
+that the tags are maintained during swap or hibernation of the host, however
+the VMM needs to manually save/restore the tags as appropriate if the VM is
+migrated.
+
+When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
+perform a bulk copy of tags to/from the guest
+
 8. Other capabilities.
 ======================
 
@@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
 KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
 for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
 vcpu_info is set.
+
-- 
2.20.1

Re: [PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl

[Peter Maydell]

On Mon, 1 Mar 2021 at 14:23, Steven Price <steven.price@arm.com> wrote:
>
> A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports
> granting a guest access to the tags, and provides a mechanism for the
> VMM to enable it.
>
> A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to
> access the tags of a guest without having to maintain a PROT_MTE mapping
> in userspace. The above capability gates access to the ioctl.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index aed52b0fc16e..1406ea138127 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
>  Allows Xen vCPU attributes to be read. For the structure and types,
>  see KVM_XEN_VCPU_SET_ATTR above.
>
> +4.131 KVM_ARM_MTE_COPY_TAGS
> +---------------------------
> +
> +:Capability: KVM_CAP_ARM_MTE
> +:Architectures: arm64
> +:Type: vm ioctl
> +:Parameters: struct kvm_arm_copy_mte_tags
> +:Returns: 0 on success, < 0 on error
> +
> +Copies Memory Tagging Extension (MTE) tags to/from guest tag memory.

Mostly virt/kvm/api.rst seems to include documentation of the
associated structs, something like:

::

  struct kvm_arm_copy_mte_tags {
         __u64 guest_ipa;
         __u64 length;
         union {
                 void __user *addr;
                 __u64 padding;
         };
         __u64 flags;
  };


which saves the reader having to cross-reference against the header file.
It also means you can more naturally use the actual field names in the doc,
eg:

> +The
> +starting address and length of guest memory must be ``PAGE_SIZE`` aligned.

you could say "The guest_ipa and length fields" here.

Also "The addr field must point to a buffer which the tags will
be copied to or from." I assume.

> +The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)``
> +bytes (i.e. 1/16th of the corresponding size).

> + Each byte contains a single tag
> +value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
> +``PTRACE_POKEMTETAGS``.

What are the valid values for 'flags' ? It looks like they specify which
direction the copy is, which we definitely need to document here.

What happens if the caller requests a tag copy for an area of guest
address space which doesn't have tags (eg it has nothing mapped),
or for an area of guest addres space which has tags in some parts
but not in others ?

> +
>  5. The kvm_run structure
>  ========================
>
> @@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
>  This capability can be used to check / enable 2nd DAWR feature provided
>  by POWER10 processor.
>
> +7.23 KVM_CAP_ARM_MTE
> +--------------------
> +
> +:Architectures: arm64
> +:Parameters: none
> +
> +This capability indicates that KVM (and the hardware) supports exposing the
> +Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the
> +VMM before the guest will be granted access.
> +
> +When enabled the guest is able to access tags associated with any memory given
> +to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so
> +that the tags are maintained during swap or hibernation of the host, however

s/,/;/

> +the VMM needs to manually save/restore the tags as appropriate if the VM is
> +migrated.
> +
> +When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
> +perform a bulk copy of tags to/from the guest

"guest."

> +
>  8. Other capabilities.
>  ======================
>
> @@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
>  KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
>  for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
>  vcpu_info is set.
> +
> --
> 2.20.1


Stray whitespace change ?

thanks
-- PMM

Re: [PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl

[Peter Maydell]

On Mon, 1 Mar 2021 at 14:23, Steven Price <steven.price@arm.com> wrote:
>
> A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports
> granting a guest access to the tags, and provides a mechanism for the
> VMM to enable it.
>
> A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to
> access the tags of a guest without having to maintain a PROT_MTE mapping
> in userspace. The above capability gates access to the ioctl.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index aed52b0fc16e..1406ea138127 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
>  Allows Xen vCPU attributes to be read. For the structure and types,
>  see KVM_XEN_VCPU_SET_ATTR above.
>
> +4.131 KVM_ARM_MTE_COPY_TAGS
> +---------------------------
> +
> +:Capability: KVM_CAP_ARM_MTE
> +:Architectures: arm64
> +:Type: vm ioctl
> +:Parameters: struct kvm_arm_copy_mte_tags
> +:Returns: 0 on success, < 0 on error
> +
> +Copies Memory Tagging Extension (MTE) tags to/from guest tag memory.

Mostly virt/kvm/api.rst seems to include documentation of the
associated structs, something like:

::

  struct kvm_arm_copy_mte_tags {
         __u64 guest_ipa;
         __u64 length;
         union {
                 void __user *addr;
                 __u64 padding;
         };
         __u64 flags;
  };


which saves the reader having to cross-reference against the header file.
It also means you can more naturally use the actual field names in the doc,
eg:

> +The
> +starting address and length of guest memory must be ``PAGE_SIZE`` aligned.

you could say "The guest_ipa and length fields" here.

Also "The addr field must point to a buffer which the tags will
be copied to or from." I assume.

> +The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)``
> +bytes (i.e. 1/16th of the corresponding size).

> + Each byte contains a single tag
> +value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
> +``PTRACE_POKEMTETAGS``.

What are the valid values for 'flags' ? It looks like they specify which
direction the copy is, which we definitely need to document here.

What happens if the caller requests a tag copy for an area of guest
address space which doesn't have tags (eg it has nothing mapped),
or for an area of guest addres space which has tags in some parts
but not in others ?

> +
>  5. The kvm_run structure
>  ========================
>
> @@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
>  This capability can be used to check / enable 2nd DAWR feature provided
>  by POWER10 processor.
>
> +7.23 KVM_CAP_ARM_MTE
> +--------------------
> +
> +:Architectures: arm64
> +:Parameters: none
> +
> +This capability indicates that KVM (and the hardware) supports exposing the
> +Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the
> +VMM before the guest will be granted access.
> +
> +When enabled the guest is able to access tags associated with any memory given
> +to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so
> +that the tags are maintained during swap or hibernation of the host, however

s/,/;/

> +the VMM needs to manually save/restore the tags as appropriate if the VM is
> +migrated.
> +
> +When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
> +perform a bulk copy of tags to/from the guest

"guest."

> +
>  8. Other capabilities.
>  ======================
>
> @@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
>  KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
>  for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
>  vcpu_info is set.
> +
> --
> 2.20.1


Stray whitespace change ?

thanks
-- PMM

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl

[Peter Maydell]

On Mon, 1 Mar 2021 at 14:23, Steven Price <steven.price@arm.com> wrote:
>
> A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports
> granting a guest access to the tags, and provides a mechanism for the
> VMM to enable it.
>
> A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to
> access the tags of a guest without having to maintain a PROT_MTE mapping
> in userspace. The above capability gates access to the ioctl.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index aed52b0fc16e..1406ea138127 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
>  Allows Xen vCPU attributes to be read. For the structure and types,
>  see KVM_XEN_VCPU_SET_ATTR above.
>
> +4.131 KVM_ARM_MTE_COPY_TAGS
> +---------------------------
> +
> +:Capability: KVM_CAP_ARM_MTE
> +:Architectures: arm64
> +:Type: vm ioctl
> +:Parameters: struct kvm_arm_copy_mte_tags
> +:Returns: 0 on success, < 0 on error
> +
> +Copies Memory Tagging Extension (MTE) tags to/from guest tag memory.

Mostly virt/kvm/api.rst seems to include documentation of the
associated structs, something like:

::

  struct kvm_arm_copy_mte_tags {
         __u64 guest_ipa;
         __u64 length;
         union {
                 void __user *addr;
                 __u64 padding;
         };
         __u64 flags;
  };


which saves the reader having to cross-reference against the header file.
It also means you can more naturally use the actual field names in the doc,
eg:

> +The
> +starting address and length of guest memory must be ``PAGE_SIZE`` aligned.

you could say "The guest_ipa and length fields" here.

Also "The addr field must point to a buffer which the tags will
be copied to or from." I assume.

> +The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)``
> +bytes (i.e. 1/16th of the corresponding size).

> + Each byte contains a single tag
> +value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
> +``PTRACE_POKEMTETAGS``.

What are the valid values for 'flags' ? It looks like they specify which
direction the copy is, which we definitely need to document here.

What happens if the caller requests a tag copy for an area of guest
address space which doesn't have tags (eg it has nothing mapped),
or for an area of guest addres space which has tags in some parts
but not in others ?

> +
>  5. The kvm_run structure
>  ========================
>
> @@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
>  This capability can be used to check / enable 2nd DAWR feature provided
>  by POWER10 processor.
>
> +7.23 KVM_CAP_ARM_MTE
> +--------------------
> +
> +:Architectures: arm64
> +:Parameters: none
> +
> +This capability indicates that KVM (and the hardware) supports exposing the
> +Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the
> +VMM before the guest will be granted access.
> +
> +When enabled the guest is able to access tags associated with any memory given
> +to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so
> +that the tags are maintained during swap or hibernation of the host, however

s/,/;/

> +the VMM needs to manually save/restore the tags as appropriate if the VM is
> +migrated.
> +
> +When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
> +perform a bulk copy of tags to/from the guest

"guest."

> +
>  8. Other capabilities.
>  ======================
>
> @@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
>  KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
>  for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
>  vcpu_info is set.
> +
> --
> 2.20.1


Stray whitespace change ?

thanks
-- PMM
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

Re: [PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl

[Peter Maydell]

On Mon, 1 Mar 2021 at 14:23, Steven Price <steven.price@arm.com> wrote:
>
> A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports
> granting a guest access to the tags, and provides a mechanism for the
> VMM to enable it.
>
> A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to
> access the tags of a guest without having to maintain a PROT_MTE mapping
> in userspace. The above capability gates access to the ioctl.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index aed52b0fc16e..1406ea138127 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
>  Allows Xen vCPU attributes to be read. For the structure and types,
>  see KVM_XEN_VCPU_SET_ATTR above.
>
> +4.131 KVM_ARM_MTE_COPY_TAGS
> +---------------------------
> +
> +:Capability: KVM_CAP_ARM_MTE
> +:Architectures: arm64
> +:Type: vm ioctl
> +:Parameters: struct kvm_arm_copy_mte_tags
> +:Returns: 0 on success, < 0 on error
> +
> +Copies Memory Tagging Extension (MTE) tags to/from guest tag memory.

Mostly virt/kvm/api.rst seems to include documentation of the
associated structs, something like:

::

  struct kvm_arm_copy_mte_tags {
         __u64 guest_ipa;
         __u64 length;
         union {
                 void __user *addr;
                 __u64 padding;
         };
         __u64 flags;
  };


which saves the reader having to cross-reference against the header file.
It also means you can more naturally use the actual field names in the doc,
eg:

> +The
> +starting address and length of guest memory must be ``PAGE_SIZE`` aligned.

you could say "The guest_ipa and length fields" here.

Also "The addr field must point to a buffer which the tags will
be copied to or from." I assume.

> +The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)``
> +bytes (i.e. 1/16th of the corresponding size).

> + Each byte contains a single tag
> +value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
> +``PTRACE_POKEMTETAGS``.

What are the valid values for 'flags' ? It looks like they specify which
direction the copy is, which we definitely need to document here.

What happens if the caller requests a tag copy for an area of guest
address space which doesn't have tags (eg it has nothing mapped),
or for an area of guest addres space which has tags in some parts
but not in others ?

> +
>  5. The kvm_run structure
>  ========================
>
> @@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
>  This capability can be used to check / enable 2nd DAWR feature provided
>  by POWER10 processor.
>
> +7.23 KVM_CAP_ARM_MTE
> +--------------------
> +
> +:Architectures: arm64
> +:Parameters: none
> +
> +This capability indicates that KVM (and the hardware) supports exposing the
> +Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the
> +VMM before the guest will be granted access.
> +
> +When enabled the guest is able to access tags associated with any memory given
> +to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so
> +that the tags are maintained during swap or hibernation of the host, however

s/,/;/

> +the VMM needs to manually save/restore the tags as appropriate if the VM is
> +migrated.
> +
> +When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
> +perform a bulk copy of tags to/from the guest

"guest."

> +
>  8. Other capabilities.
>  ======================
>
> @@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
>  KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
>  for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
>  vcpu_info is set.
> +
> --
> 2.20.1


Stray whitespace change ?

thanks
-- PMM

Re: [PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl

[Steven Price]

On 09/03/2021 11:01, Peter Maydell wrote:
> On Mon, 1 Mar 2021 at 14:23, Steven Price <steven.price@arm.com> wrote:
>>
>> A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports
>> granting a guest access to the tags, and provides a mechanism for the
>> VMM to enable it.
>>
>> A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to
>> access the tags of a guest without having to maintain a PROT_MTE mapping
>> in userspace. The above capability gates access to the ioctl.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++
>>   1 file changed, 37 insertions(+)
>>
>> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
>> index aed52b0fc16e..1406ea138127 100644
>> --- a/Documentation/virt/kvm/api.rst
>> +++ b/Documentation/virt/kvm/api.rst
>> @@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
>>   Allows Xen vCPU attributes to be read. For the structure and types,
>>   see KVM_XEN_VCPU_SET_ATTR above.
>>
>> +4.131 KVM_ARM_MTE_COPY_TAGS
>> +---------------------------
>> +
>> +:Capability: KVM_CAP_ARM_MTE
>> +:Architectures: arm64
>> +:Type: vm ioctl
>> +:Parameters: struct kvm_arm_copy_mte_tags
>> +:Returns: 0 on success, < 0 on error
>> +
>> +Copies Memory Tagging Extension (MTE) tags to/from guest tag memory.
> 
> Mostly virt/kvm/api.rst seems to include documentation of the
> associated structs, something like:
> 
> ::
> 
>    struct kvm_arm_copy_mte_tags {
>           __u64 guest_ipa;
>           __u64 length;
>           union {
>                   void __user *addr;
>                   __u64 padding;
>           };
>           __u64 flags;
>    };
> 
> 
> which saves the reader having to cross-reference against the header file.

Good point - I'll add that.

> It also means you can more naturally use the actual field names in the doc,
> eg:
> 
>> +The
>> +starting address and length of guest memory must be ``PAGE_SIZE`` aligned.
> 
> you could say "The guest_ipa and length fields" here.
> 
> Also "The addr field must point to a buffer which the tags will
> be copied to or from." I assume.

Indeed - I'll add the clarification.

>> +The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)``
>> +bytes (i.e. 1/16th of the corresponding size).
> 
>> + Each byte contains a single tag
>> +value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
>> +``PTRACE_POKEMTETAGS``.
> 
> What are the valid values for 'flags' ? It looks like they specify which
> direction the copy is, which we definitely need to document here.

Yes either KVM_ARM_TAGS_TO_GUEST or KVM_ARM_TAGS_FROM_GUEST - again I'll 
clarify that.

> What happens if the caller requests a tag copy for an area of guest
> address space which doesn't have tags (eg it has nothing mapped),
> or for an area of guest addres space which has tags in some parts
> but not in others ?

Guest memory either exists (and has tags) or doesn't exist (assuming MTE 
is enabled for the guest). So the cases this can fail are:

  * The region isn't completely covered with memslots
  * The region isn't completely writable (and KVM_ARM_TAGS_TO_GUEST is 
specified).
  * User space doesn't have access to the memory (i.e. the memory would 
SIGSEGV or similar if the VMM accessed it).

Currently all the above produce the error -ENOENT, which now I come to 
enumerate the cases doesn't seem like a great error code (it's really 
only appropriate for the first)! Perhaps -EFAULT would be better.

>> +
>>   5. The kvm_run structure
>>   ========================
>>
>> @@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
>>   This capability can be used to check / enable 2nd DAWR feature provided
>>   by POWER10 processor.
>>
>> +7.23 KVM_CAP_ARM_MTE
>> +--------------------
>> +
>> +:Architectures: arm64
>> +:Parameters: none
>> +
>> +This capability indicates that KVM (and the hardware) supports exposing the
>> +Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the
>> +VMM before the guest will be granted access.
>> +
>> +When enabled the guest is able to access tags associated with any memory given
>> +to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so
>> +that the tags are maintained during swap or hibernation of the host, however
> 
> s/,/;/

Yep

>> +the VMM needs to manually save/restore the tags as appropriate if the VM is
>> +migrated.
>> +
>> +When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
>> +perform a bulk copy of tags to/from the guest
> 
> "guest."

Good spot.

>> +
>>   8. Other capabilities.
>>   ======================
>>
>> @@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
>>   KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
>>   for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
>>   vcpu_info is set.
>> +
>> --
>> 2.20.1
> 
> 
> Stray whitespace change ?

Not sure how that got there - but will remove.

Thanks,

Steve

Re: [PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl

[Steven Price]

On 09/03/2021 11:01, Peter Maydell wrote:
> On Mon, 1 Mar 2021 at 14:23, Steven Price <steven.price@arm.com> wrote:
>>
>> A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports
>> granting a guest access to the tags, and provides a mechanism for the
>> VMM to enable it.
>>
>> A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to
>> access the tags of a guest without having to maintain a PROT_MTE mapping
>> in userspace. The above capability gates access to the ioctl.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++
>>   1 file changed, 37 insertions(+)
>>
>> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
>> index aed52b0fc16e..1406ea138127 100644
>> --- a/Documentation/virt/kvm/api.rst
>> +++ b/Documentation/virt/kvm/api.rst
>> @@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
>>   Allows Xen vCPU attributes to be read. For the structure and types,
>>   see KVM_XEN_VCPU_SET_ATTR above.
>>
>> +4.131 KVM_ARM_MTE_COPY_TAGS
>> +---------------------------
>> +
>> +:Capability: KVM_CAP_ARM_MTE
>> +:Architectures: arm64
>> +:Type: vm ioctl
>> +:Parameters: struct kvm_arm_copy_mte_tags
>> +:Returns: 0 on success, < 0 on error
>> +
>> +Copies Memory Tagging Extension (MTE) tags to/from guest tag memory.
> 
> Mostly virt/kvm/api.rst seems to include documentation of the
> associated structs, something like:
> 
> ::
> 
>    struct kvm_arm_copy_mte_tags {
>           __u64 guest_ipa;
>           __u64 length;
>           union {
>                   void __user *addr;
>                   __u64 padding;
>           };
>           __u64 flags;
>    };
> 
> 
> which saves the reader having to cross-reference against the header file.

Good point - I'll add that.

> It also means you can more naturally use the actual field names in the doc,
> eg:
> 
>> +The
>> +starting address and length of guest memory must be ``PAGE_SIZE`` aligned.
> 
> you could say "The guest_ipa and length fields" here.
> 
> Also "The addr field must point to a buffer which the tags will
> be copied to or from." I assume.

Indeed - I'll add the clarification.

>> +The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)``
>> +bytes (i.e. 1/16th of the corresponding size).
> 
>> + Each byte contains a single tag
>> +value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
>> +``PTRACE_POKEMTETAGS``.
> 
> What are the valid values for 'flags' ? It looks like they specify which
> direction the copy is, which we definitely need to document here.

Yes either KVM_ARM_TAGS_TO_GUEST or KVM_ARM_TAGS_FROM_GUEST - again I'll 
clarify that.

> What happens if the caller requests a tag copy for an area of guest
> address space which doesn't have tags (eg it has nothing mapped),
> or for an area of guest addres space which has tags in some parts
> but not in others ?

Guest memory either exists (and has tags) or doesn't exist (assuming MTE 
is enabled for the guest). So the cases this can fail are:

  * The region isn't completely covered with memslots
  * The region isn't completely writable (and KVM_ARM_TAGS_TO_GUEST is 
specified).
  * User space doesn't have access to the memory (i.e. the memory would 
SIGSEGV or similar if the VMM accessed it).

Currently all the above produce the error -ENOENT, which now I come to 
enumerate the cases doesn't seem like a great error code (it's really 
only appropriate for the first)! Perhaps -EFAULT would be better.

>> +
>>   5. The kvm_run structure
>>   ========================
>>
>> @@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
>>   This capability can be used to check / enable 2nd DAWR feature provided
>>   by POWER10 processor.
>>
>> +7.23 KVM_CAP_ARM_MTE
>> +--------------------
>> +
>> +:Architectures: arm64
>> +:Parameters: none
>> +
>> +This capability indicates that KVM (and the hardware) supports exposing the
>> +Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the
>> +VMM before the guest will be granted access.
>> +
>> +When enabled the guest is able to access tags associated with any memory given
>> +to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so
>> +that the tags are maintained during swap or hibernation of the host, however
> 
> s/,/;/

Yep

>> +the VMM needs to manually save/restore the tags as appropriate if the VM is
>> +migrated.
>> +
>> +When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
>> +perform a bulk copy of tags to/from the guest
> 
> "guest."

Good spot.

>> +
>>   8. Other capabilities.
>>   ======================
>>
>> @@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
>>   KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
>>   for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
>>   vcpu_info is set.
>> +
>> --
>> 2.20.1
> 
> 
> Stray whitespace change ?

Not sure how that got there - but will remove.

Thanks,

Steve

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl

[Steven Price]

On 09/03/2021 11:01, Peter Maydell wrote:
> On Mon, 1 Mar 2021 at 14:23, Steven Price <steven.price@arm.com> wrote:
>>
>> A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports
>> granting a guest access to the tags, and provides a mechanism for the
>> VMM to enable it.
>>
>> A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to
>> access the tags of a guest without having to maintain a PROT_MTE mapping
>> in userspace. The above capability gates access to the ioctl.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++
>>   1 file changed, 37 insertions(+)
>>
>> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
>> index aed52b0fc16e..1406ea138127 100644
>> --- a/Documentation/virt/kvm/api.rst
>> +++ b/Documentation/virt/kvm/api.rst
>> @@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
>>   Allows Xen vCPU attributes to be read. For the structure and types,
>>   see KVM_XEN_VCPU_SET_ATTR above.
>>
>> +4.131 KVM_ARM_MTE_COPY_TAGS
>> +---------------------------
>> +
>> +:Capability: KVM_CAP_ARM_MTE
>> +:Architectures: arm64
>> +:Type: vm ioctl
>> +:Parameters: struct kvm_arm_copy_mte_tags
>> +:Returns: 0 on success, < 0 on error
>> +
>> +Copies Memory Tagging Extension (MTE) tags to/from guest tag memory.
> 
> Mostly virt/kvm/api.rst seems to include documentation of the
> associated structs, something like:
> 
> ::
> 
>    struct kvm_arm_copy_mte_tags {
>           __u64 guest_ipa;
>           __u64 length;
>           union {
>                   void __user *addr;
>                   __u64 padding;
>           };
>           __u64 flags;
>    };
> 
> 
> which saves the reader having to cross-reference against the header file.

Good point - I'll add that.

> It also means you can more naturally use the actual field names in the doc,
> eg:
> 
>> +The
>> +starting address and length of guest memory must be ``PAGE_SIZE`` aligned.
> 
> you could say "The guest_ipa and length fields" here.
> 
> Also "The addr field must point to a buffer which the tags will
> be copied to or from." I assume.

Indeed - I'll add the clarification.

>> +The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)``
>> +bytes (i.e. 1/16th of the corresponding size).
> 
>> + Each byte contains a single tag
>> +value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
>> +``PTRACE_POKEMTETAGS``.
> 
> What are the valid values for 'flags' ? It looks like they specify which
> direction the copy is, which we definitely need to document here.

Yes either KVM_ARM_TAGS_TO_GUEST or KVM_ARM_TAGS_FROM_GUEST - again I'll 
clarify that.

> What happens if the caller requests a tag copy for an area of guest
> address space which doesn't have tags (eg it has nothing mapped),
> or for an area of guest addres space which has tags in some parts
> but not in others ?

Guest memory either exists (and has tags) or doesn't exist (assuming MTE 
is enabled for the guest). So the cases this can fail are:

  * The region isn't completely covered with memslots
  * The region isn't completely writable (and KVM_ARM_TAGS_TO_GUEST is 
specified).
  * User space doesn't have access to the memory (i.e. the memory would 
SIGSEGV or similar if the VMM accessed it).

Currently all the above produce the error -ENOENT, which now I come to 
enumerate the cases doesn't seem like a great error code (it's really 
only appropriate for the first)! Perhaps -EFAULT would be better.

>> +
>>   5. The kvm_run structure
>>   ========================
>>
>> @@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
>>   This capability can be used to check / enable 2nd DAWR feature provided
>>   by POWER10 processor.
>>
>> +7.23 KVM_CAP_ARM_MTE
>> +--------------------
>> +
>> +:Architectures: arm64
>> +:Parameters: none
>> +
>> +This capability indicates that KVM (and the hardware) supports exposing the
>> +Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the
>> +VMM before the guest will be granted access.
>> +
>> +When enabled the guest is able to access tags associated with any memory given
>> +to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so
>> +that the tags are maintained during swap or hibernation of the host, however
> 
> s/,/;/

Yep

>> +the VMM needs to manually save/restore the tags as appropriate if the VM is
>> +migrated.
>> +
>> +When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
>> +perform a bulk copy of tags to/from the guest
> 
> "guest."

Good spot.

>> +
>>   8. Other capabilities.
>>   ======================
>>
>> @@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
>>   KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
>>   for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
>>   vcpu_info is set.
>> +
>> --
>> 2.20.1
> 
> 
> Stray whitespace change ?

Not sure how that got there - but will remove.

Thanks,

Steve
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

Re: [PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl

[Steven Price]

On 09/03/2021 11:01, Peter Maydell wrote:
> On Mon, 1 Mar 2021 at 14:23, Steven Price <steven.price@arm.com> wrote:
>>
>> A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports
>> granting a guest access to the tags, and provides a mechanism for the
>> VMM to enable it.
>>
>> A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to
>> access the tags of a guest without having to maintain a PROT_MTE mapping
>> in userspace. The above capability gates access to the ioctl.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>   Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++
>>   1 file changed, 37 insertions(+)
>>
>> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
>> index aed52b0fc16e..1406ea138127 100644
>> --- a/Documentation/virt/kvm/api.rst
>> +++ b/Documentation/virt/kvm/api.rst
>> @@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
>>   Allows Xen vCPU attributes to be read. For the structure and types,
>>   see KVM_XEN_VCPU_SET_ATTR above.
>>
>> +4.131 KVM_ARM_MTE_COPY_TAGS
>> +---------------------------
>> +
>> +:Capability: KVM_CAP_ARM_MTE
>> +:Architectures: arm64
>> +:Type: vm ioctl
>> +:Parameters: struct kvm_arm_copy_mte_tags
>> +:Returns: 0 on success, < 0 on error
>> +
>> +Copies Memory Tagging Extension (MTE) tags to/from guest tag memory.
> 
> Mostly virt/kvm/api.rst seems to include documentation of the
> associated structs, something like:
> 
> ::
> 
>    struct kvm_arm_copy_mte_tags {
>           __u64 guest_ipa;
>           __u64 length;
>           union {
>                   void __user *addr;
>                   __u64 padding;
>           };
>           __u64 flags;
>    };
> 
> 
> which saves the reader having to cross-reference against the header file.

Good point - I'll add that.

> It also means you can more naturally use the actual field names in the doc,
> eg:
> 
>> +The
>> +starting address and length of guest memory must be ``PAGE_SIZE`` aligned.
> 
> you could say "The guest_ipa and length fields" here.
> 
> Also "The addr field must point to a buffer which the tags will
> be copied to or from." I assume.

Indeed - I'll add the clarification.

>> +The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)``
>> +bytes (i.e. 1/16th of the corresponding size).
> 
>> + Each byte contains a single tag
>> +value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
>> +``PTRACE_POKEMTETAGS``.
> 
> What are the valid values for 'flags' ? It looks like they specify which
> direction the copy is, which we definitely need to document here.

Yes either KVM_ARM_TAGS_TO_GUEST or KVM_ARM_TAGS_FROM_GUEST - again I'll 
clarify that.

> What happens if the caller requests a tag copy for an area of guest
> address space which doesn't have tags (eg it has nothing mapped),
> or for an area of guest addres space which has tags in some parts
> but not in others ?

Guest memory either exists (and has tags) or doesn't exist (assuming MTE 
is enabled for the guest). So the cases this can fail are:

  * The region isn't completely covered with memslots
  * The region isn't completely writable (and KVM_ARM_TAGS_TO_GUEST is 
specified).
  * User space doesn't have access to the memory (i.e. the memory would 
SIGSEGV or similar if the VMM accessed it).

Currently all the above produce the error -ENOENT, which now I come to 
enumerate the cases doesn't seem like a great error code (it's really 
only appropriate for the first)! Perhaps -EFAULT would be better.

>> +
>>   5. The kvm_run structure
>>   ========================
>>
>> @@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
>>   This capability can be used to check / enable 2nd DAWR feature provided
>>   by POWER10 processor.
>>
>> +7.23 KVM_CAP_ARM_MTE
>> +--------------------
>> +
>> +:Architectures: arm64
>> +:Parameters: none
>> +
>> +This capability indicates that KVM (and the hardware) supports exposing the
>> +Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the
>> +VMM before the guest will be granted access.
>> +
>> +When enabled the guest is able to access tags associated with any memory given
>> +to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so
>> +that the tags are maintained during swap or hibernation of the host, however
> 
> s/,/;/

Yep

>> +the VMM needs to manually save/restore the tags as appropriate if the VM is
>> +migrated.
>> +
>> +When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
>> +perform a bulk copy of tags to/from the guest
> 
> "guest."

Good spot.

>> +
>>   8. Other capabilities.
>>   ======================
>>
>> @@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
>>   KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
>>   for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
>>   vcpu_info is set.
>> +
>> --
>> 2.20.1
> 
> 
> Stray whitespace change ?

Not sure how that got there - but will remove.

Thanks,

Steve