[PATCH v9 00/18] KVM: s390: pv: implement lazy destroy for reboot

[PATCH v9 00/18] KVM: s390: pv: implement lazy destroy for reboot

[Claudio Imbrenda]

Previously, when a protected VM was rebooted or when it was shut down,
its memory was made unprotected, and then the protected VM itself was
destroyed. Looping over the whole address space can take some time,
considering the overhead of the various Ultravisor Calls (UVCs). This
means that a reboot or a shutdown would take a potentially long amount
of time, depending on the amount of used memory.

This patchseries implements a deferred destroy mechanism for protected
guests. When a protected guest is destroyed, its memory can be cleared
in background, allowing the guest to restart or terminate significantly
faster than before.

There are 2 possibilities when a protected VM is torn down:
* it still has an address space associated (reboot case)
* it does not have an address space anymore (shutdown case)

For the reboot case, two new commands are available for the
KVM_S390_PV_COMMAND:

KVM_PV_ASYNC_DISABLE_PREPARE: prepares the current protected VM for
asynchronous teardown. The current VM will then continue immediately
as non-protected. If a protected VM had already been set aside without
starting the teardown process, this call will fail. In this case the
userspace process should issue a normal KVM_PV_DISABLE

KVM_PV_ASYNC_DISABLE: tears down the protected VM previously set aside
for asychronous teardown. This PV command should ideally be issued by
userspace from a separate thread. If a fatal signal is received (or
the process terminates naturally), the command will terminate
immediately without completing.

The idea is that userspace should first issue the
KVM_PV_ASYNC_DISABLE_PREPARE command, and in case of success, create a
new thread and issue KVM_PV_ASYNC_DISABLE from there. This also allows
for proper accounting of the CPU time needed for the asynchronous
teardown.

This means that the same address space can have memory belonging to
more than one protected guest, although only one will be running, the
others will in fact not even have any CPUs.

The shutdown case should be dealt with in userspace (e.g. using
clone(CLONE_VM)).

A module parameter is also provided to disable the new functionality,
which is otherwise enabled by default. This should not be an issue
since the new functionality is opt-in anyway. This is mainly thought to
aid debugging.

v8->v9
* rebased
* added dependency on MMU_NOTIFIER for KVM in arch/s390/kvm/Kconfig
* add support for the Destroy Secure Configuration Fast UVC
* minor fixes

v7->v8
* switched patches 8 and 9
* improved comments, documentation and patch descriptions
* remove mm notifier when the struct kvm is torn down
* removed useless locks in the mm notifier
* use _ASCE_ORIGIN instead of PAGE_MASK for ASCEs
* cleanup of some compiler warnings
* remove some harmless but useless duplicate code
* the last parameter of __s390_uv_destroy_range is now bool
* rename the KVM capability to KVM_CAP_S390_PROTECTED_ASYNC_DISABLE

v6->v7
* moved INIT_LIST_HEAD inside spinlock in patch 1
* improved commit messages in patch 2
* added missing locks in patch 3
* added and expanded some comments in patch 11
* rebased

v5->v6
* completely reworked the series
* removed kernel thread for asynchronous teardown
* added new commands to KVM_S390_PV_COMMAND ioctl

v4->v5
* fixed and improved some patch descriptions
* added some comments to better explain what's going on
* use vma_lookup instead of find_vma
* rename is_protected to protected_count since now it's used as a counter

v3->v4
* added patch 2
* split patch 3
* removed the shutdown part -- will be a separate patchseries
* moved the patch introducing the module parameter

v2->v3
* added definitions for CC return codes for the UVC instruction
* improved make_secure_pte:
  - renamed rc to cc
  - added comments to explain why returning -EAGAIN is ok
* fixed kvm_s390_pv_replace_asce and kvm_s390_pv_remove_old_asce:
  - renamed
  - added locking
  - moved to gmap.c
* do proper error management in do_secure_storage_access instead of
  trying again hoping to get a different exception
* fix outdated patch descriptions

v1->v2
* rebased on a more recent kernel
* improved/expanded some patch descriptions
* improves/expanded some comments
* added patch 1, which prevents stall notification when the system is
  under heavy load.
* rename some members of struct deferred_priv to improve readability
* avoid an use-after-free bug of the struct mm in case of shutdown
* add missing return when lazy destroy is disabled
* add support for OOM notifier

Claudio Imbrenda (18):
  KVM: s390: pv: leak the topmost page table when destroy fails
  KVM: s390: pv: handle secure storage violations for protected guests
  KVM: s390: pv: handle secure storage exceptions for normal guests
  KVM: s390: pv: refactor s390_reset_acc
  KVM: s390: pv: usage counter instead of flag
  KVM: s390: pv: add export before import
  KVM: s390: pv: module parameter to fence lazy destroy
  KVM: s390: pv: clear the state without memset
  KVM: s390: pv: Add kvm_s390_cpus_from_pv to kvm-s390.h and add
    documentation
  KVM: s390: pv: add mmu_notifier
  s390/mm: KVM: pv: when tearing down, try to destroy protected pages
  KVM: s390: pv: refactoring of kvm_s390_pv_deinit_vm
  KVM: s390: pv: cleanup leftover protected VMs if needed
  KVM: s390: pv: asynchronous destroy for reboot
  KVM: s390: pv: api documentation for asynchronous destroy
  KVM: s390: pv: add KVM_CAP_S390_PROTECTED_ASYNC_DISABLE
  KVM: s390: pv: avoid export before import if possible
  KVM: s390: pv: support for Destroy fast UVC

 Documentation/virt/kvm/api.rst      |  25 ++-
 arch/s390/include/asm/gmap.h        |  39 +++-
 arch/s390/include/asm/kvm_host.h    |   4 +
 arch/s390/include/asm/mmu.h         |   2 +-
 arch/s390/include/asm/mmu_context.h |   2 +-
 arch/s390/include/asm/pgtable.h     |  20 +-
 arch/s390/include/asm/uv.h          |  11 ++
 arch/s390/kernel/uv.c               |  64 ++++++
 arch/s390/kvm/Kconfig               |   1 +
 arch/s390/kvm/kvm-s390.c            |  64 +++++-
 arch/s390/kvm/kvm-s390.h            |   3 +
 arch/s390/kvm/pv.c                  | 297 +++++++++++++++++++++++++++-
 arch/s390/mm/fault.c                |  23 ++-
 arch/s390/mm/gmap.c                 | 158 ++++++++++++---
 include/uapi/linux/kvm.h            |   3 +
 15 files changed, 670 insertions(+), 46 deletions(-)

-- 
2.34.1

[PATCH v9 01/18] KVM: s390: pv: leak the topmost page table when destroy fails

[Claudio Imbrenda]

Each secure guest must have a unique ASCE (address space control
element); we must avoid that new guests use the same page for their
ASCE, to avoid errors.

Since the ASCE mostly consists of the address of the topmost page table
(plus some flags), we must not return that memory to the pool unless
the ASCE is no longer in use.

Only a successful Destroy Secure Configuration UVC will make the ASCE
reusable again.

If the Destroy Configuration UVC fails, the ASCE cannot be reused for a
secure guest (either for the ASCE or for other memory areas). To avoid
a collision, it must not be used again. This is a permanent error and
the page becomes in practice unusable, so we set it aside and leak it.
On failure we already leak other memory that belongs to the ultravisor
(i.e. the variable and base storage for a guest) and not leaking the
topmost page table was an oversight.

This error (and thus the leakage) should not happen unless the hardware
is broken or KVM has some unknown serious bug.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Fixes: 29b40f105ec8d55 ("KVM: s390: protvirt: Add initial vm and cpu lifecycle handling")
---
 arch/s390/include/asm/gmap.h |  2 +
 arch/s390/kvm/pv.c           |  9 +++--
 arch/s390/mm/gmap.c          | 71 ++++++++++++++++++++++++++++++++++++
 3 files changed, 79 insertions(+), 3 deletions(-)

diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
index 40264f60b0da..746e18bf8984 100644
--- a/arch/s390/include/asm/gmap.h
+++ b/arch/s390/include/asm/gmap.h
@@ -148,4 +148,6 @@ void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long dirty_bitmap[4],
 			     unsigned long gaddr, unsigned long vmaddr);
 int gmap_mark_unmergeable(void);
 void s390_reset_acc(struct mm_struct *mm);
+void s390_remove_old_asce(struct gmap *gmap);
+int s390_replace_asce(struct gmap *gmap);
 #endif /* _ASM_S390_GMAP_H */
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 7f7c0d6af2ce..3c59ef763dde 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -166,10 +166,13 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 	atomic_set(&kvm->mm->context.is_protected, 0);
 	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
 	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
-	/* Inteded memory leak on "impossible" error */
-	if (!cc)
+	/* Intended memory leak on "impossible" error */
+	if (!cc) {
 		kvm_s390_pv_dealloc_vm(kvm);
-	return cc ? -EIO : 0;
+		return 0;
+	}
+	s390_replace_asce(kvm->arch.gmap);
+	return -EIO;
 }
 
 int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index dfee0ebb2fac..3b42bf7adb77 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2714,3 +2714,74 @@ void s390_reset_acc(struct mm_struct *mm)
 	mmput(mm);
 }
 EXPORT_SYMBOL_GPL(s390_reset_acc);
+
+/**
+ * s390_remove_old_asce - Remove the topmost level of page tables from the
+ * list of page tables of the gmap.
+ * @gmap the gmap whose table is to be removed
+ *
+ * This means that it will not be freed when the VM is torn down, and needs
+ * to be handled separately by the caller, unless an intentional leak is
+ * intended. Notice that this function will only remove the page from the
+ * list, the page will still be used as a top level page table (and ASCE).
+ */
+void s390_remove_old_asce(struct gmap *gmap)
+{
+	struct page *old;
+
+	old = virt_to_page(gmap->table);
+	spin_lock(&gmap->guest_table_lock);
+	list_del(&old->lru);
+	/*
+	 * in case the ASCE needs to be "removed" multiple times, for example
+	 * if the VM is rebooted into secure mode several times
+	 * concurrently.
+	 */
+	INIT_LIST_HEAD(&old->lru);
+	spin_unlock(&gmap->guest_table_lock);
+}
+EXPORT_SYMBOL_GPL(s390_remove_old_asce);
+
+/**
+ * s390_replace_asce - Try to replace the current ASCE of a gmap with
+ * another equivalent one.
+ * @gmap the gmap
+ *
+ * If the allocation of the new top level page table fails, the ASCE is not
+ * replaced.
+ * In any case, the old ASCE is always removed from the list. Therefore the
+ * caller has to make sure to save a pointer to it beforehands, unless an
+ * intentional leak is intended.
+ */
+int s390_replace_asce(struct gmap *gmap)
+{
+	unsigned long asce;
+	struct page *page;
+	void *table;
+
+	s390_remove_old_asce(gmap);
+
+	page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
+	if (!page)
+		return -ENOMEM;
+	table = page_to_virt(page);
+	memcpy(table, gmap->table, 1UL << (CRST_ALLOC_ORDER + PAGE_SHIFT));
+
+	/*
+	 * The caller has to deal with the old ASCE, but here we make sure
+	 * the new one is properly added to the list of page tables, so that
+	 * it will be freed when the VM is torn down.
+	 */
+	spin_lock(&gmap->guest_table_lock);
+	list_add(&page->lru, &gmap->crst_list);
+	spin_unlock(&gmap->guest_table_lock);
+
+	/* Set new table origin while preserving existing ASCE control bits */
+	asce = (gmap->asce & ~_ASCE_ORIGIN) | __pa(table);
+	WRITE_ONCE(gmap->asce, asce);
+	WRITE_ONCE(gmap->mm->context.gmap_asce, asce);
+	WRITE_ONCE(gmap->table, table);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(s390_replace_asce);
-- 
2.34.1

[PATCH v9 02/18] KVM: s390: pv: handle secure storage violations for protected guests

[Claudio Imbrenda]

With upcoming patches, protected guests will be able to trigger secure
storage violations in normal operation.

A secure storage violation is triggered when a protected guest tries to
access secure memory that has been mapped erroneously, or that belongs
to a different protected guest or to the ultravisor.

With upcoming patches, protected guests will be able to trigger secure
storage violations in normal operation. This happens for example if a
protected guest is rebooted with lazy destroy enabled and the new guest
is also protected.

When the new protected guest touches pages that have not yet been
destroyed, and thus are accounted to the previous protected guest, a
secure storage violation is raised.

This patch adds handling of secure storage violations for protected
guests.

This exception is handled by first trying to destroy the page, because
it is expected to belong to a defunct protected guest where a destroy
should be possible. If that fails, a normal export of the page is
attempted.

Therefore, pages that trigger the exception will be made non-secure
before attempting to use them again for a different secure guest.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
---
 arch/s390/include/asm/uv.h |  1 +
 arch/s390/kernel/uv.c      | 55 ++++++++++++++++++++++++++++++++++++++
 arch/s390/mm/fault.c       | 10 +++++++
 3 files changed, 66 insertions(+)

diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
index 86218382d29c..6b2b33f19abe 100644
--- a/arch/s390/include/asm/uv.h
+++ b/arch/s390/include/asm/uv.h
@@ -356,6 +356,7 @@ static inline int is_prot_virt_host(void)
 }
 
 int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb);
+int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr);
 int uv_destroy_owned_page(unsigned long paddr);
 int uv_convert_from_secure(unsigned long paddr);
 int uv_convert_owned_from_secure(unsigned long paddr);
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index a5425075dd25..2754471cc789 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -334,6 +334,61 @@ int gmap_convert_to_secure(struct gmap *gmap, unsigned long gaddr)
 }
 EXPORT_SYMBOL_GPL(gmap_convert_to_secure);
 
+/**
+ * gmap_destroy_page - Destroy a guest page.
+ * @gmap the gmap of the guest
+ * @gaddr the guest address to destroy
+ *
+ * An attempt will be made to destroy the given guest page. If the attempt
+ * fails, an attempt is made to export the page. If both attempts fail, an
+ * appropriate error is returned.
+ */
+int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr)
+{
+	struct vm_area_struct *vma;
+	unsigned long uaddr;
+	struct page *page;
+	int rc;
+
+	rc = -EFAULT;
+	mmap_read_lock(gmap->mm);
+
+	uaddr = __gmap_translate(gmap, gaddr);
+	if (IS_ERR_VALUE(uaddr))
+		goto out;
+	vma = vma_lookup(gmap->mm, uaddr);
+	if (!vma)
+		goto out;
+	/*
+	 * Huge pages should not be able to become secure
+	 */
+	if (is_vm_hugetlb_page(vma))
+		goto out;
+
+	rc = 0;
+	/* we take an extra reference here */
+	page = follow_page(vma, uaddr, FOLL_WRITE | FOLL_GET);
+	if (IS_ERR_OR_NULL(page))
+		goto out;
+	rc = uv_destroy_owned_page(page_to_phys(page));
+	/*
+	 * Fault handlers can race; it is possible that two CPUs will fault
+	 * on the same secure page. One CPU can destroy the page, reboot,
+	 * re-enter secure mode and import it, while the second CPU was
+	 * stuck at the beginning of the handler. At some point the second
+	 * CPU will be able to progress, and it will not be able to destroy
+	 * the page. In that case we do not want to terminate the process,
+	 * we instead try to export the page.
+	 */
+	if (rc)
+		rc = uv_convert_owned_from_secure(page_to_phys(page));
+	put_page(page);
+out:
+	mmap_read_unlock(gmap->mm);
+	return rc;
+}
+EXPORT_SYMBOL_GPL(gmap_destroy_page);
+
 /*
  * To be called with the page locked or with an extra reference! This will
  * prevent gmap_make_secure from touching the page concurrently. Having 2
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index ff16ce0d04ee..47b52e5384f8 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -853,6 +853,16 @@ NOKPROBE_SYMBOL(do_non_secure_storage_access);
 
 void do_secure_storage_violation(struct pt_regs *regs)
 {
+	unsigned long gaddr = regs->int_parm_long & __FAIL_ADDR_MASK;
+	struct gmap *gmap = (struct gmap *)S390_lowcore.gmap;
+
+	/*
+	 * If the VM has been rebooted, its address space might still contain
+	 * secure pages from the previous boot.
+	 * Clear the page so it can be reused.
+	 */
+	if (!gmap_destroy_page(gmap, gaddr))
+		return;
 	/*
 	 * Either KVM messed up the secure guest mapping or the same
 	 * page is mapped into multiple secure guests.
-- 
2.34.1

[PATCH v9 03/18] KVM: s390: pv: handle secure storage exceptions for normal guests

[Claudio Imbrenda]

With upcoming patches, normal guests might touch secure pages.

This patch extends the existing exception handler to convert the pages
to non secure also when the exception is triggered by a normal guest.

This can happen for example when a secure guest reboots; the first
stage of a secure guest is non secure, and in general a secure guest
can reboot into non-secure mode.

If the secure memory of the previous boot has not been cleared up
completely yet (which will be allowed to happen in an upcoming patch),
a non-secure guest might touch secure memory, which will need to be
handled properly.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
---
 arch/s390/mm/fault.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 47b52e5384f8..54571a88a641 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -770,6 +770,7 @@ void do_secure_storage_access(struct pt_regs *regs)
 	struct vm_area_struct *vma;
 	struct mm_struct *mm;
 	struct page *page;
+	struct gmap *gmap;
 	int rc;
 
 	/*
@@ -799,6 +800,17 @@ void do_secure_storage_access(struct pt_regs *regs)
 	}
 
 	switch (get_fault_type(regs)) {
+	case GMAP_FAULT:
+		mm = current->mm;
+		gmap = (struct gmap *)S390_lowcore.gmap;
+		mmap_read_lock(mm);
+		addr = __gmap_translate(gmap, addr);
+		mmap_read_unlock(mm);
+		if (IS_ERR_VALUE(addr)) {
+			do_fault_error(regs, VM_ACCESS_FLAGS, VM_FAULT_BADMAP);
+			break;
+		}
+		fallthrough;
 	case USER_FAULT:
 		mm = current->mm;
 		mmap_read_lock(mm);
@@ -827,7 +839,6 @@ void do_secure_storage_access(struct pt_regs *regs)
 		if (rc)
 			BUG();
 		break;
-	case GMAP_FAULT:
 	default:
 		do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP);
 		WARN_ON_ONCE(1);
-- 
2.34.1

[PATCH v9 04/18] KVM: s390: pv: refactor s390_reset_acc

[Claudio Imbrenda]

Refactor s390_reset_acc so that it can be reused in upcoming patches.

We don't want to hold all the locks used in a walk_page_range for too
long, and the destroy page UVC does take some time to complete.
Therefore we quickly gather the pages to destroy, and then destroy them
without holding all the locks.

The new refactored function optionally allows to return early without
completing if a fatal signal is pending (and return and appropriate
error code). Two wrappers are provided to call the new function.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
(dropping Janosch's Ack because of major changes to the patch)
---
 arch/s390/include/asm/gmap.h | 37 +++++++++++++-
 arch/s390/kvm/pv.c           | 12 ++++-
 arch/s390/mm/gmap.c          | 95 +++++++++++++++++++++++++-----------
 3 files changed, 112 insertions(+), 32 deletions(-)

diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
index 746e18bf8984..0baaa127614b 100644
--- a/arch/s390/include/asm/gmap.h
+++ b/arch/s390/include/asm/gmap.h
@@ -147,7 +147,42 @@ int gmap_mprotect_notify(struct gmap *, unsigned long start,
 void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long dirty_bitmap[4],
 			     unsigned long gaddr, unsigned long vmaddr);
 int gmap_mark_unmergeable(void);
-void s390_reset_acc(struct mm_struct *mm);
 void s390_remove_old_asce(struct gmap *gmap);
 int s390_replace_asce(struct gmap *gmap);
+void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns);
+int __s390_uv_destroy_range(struct mm_struct *mm, unsigned long start,
+			    unsigned long end, bool interruptible);
+
+/**
+ * s390_uv_destroy_range - Destroy a range of pages in the given mm.
+ * @mm the mm on which to operate on
+ * @start the start of the range
+ * @end the end of the range
+ *
+ * This function will call cond_sched, so it should not generate stalls, but
+ * it will otherwise only return when it completed.
+ */
+static inline void s390_uv_destroy_range(struct mm_struct *mm, unsigned long start,
+					 unsigned long end)
+{
+	(void)__s390_uv_destroy_range(mm, start, end, false);
+}
+
+/**
+ * s390_uv_destroy_range_interruptible - Destroy a range of pages in the
+ * given mm, but stop when a fatal signal is received.
+ * @mm the mm on which to operate on
+ * @start the start of the range
+ * @end the end of the range
+ *
+ * This function will call cond_sched, so it should not generate stalls. If
+ * a fatal signal is received, it will return with -EINTR immediately,
+ * without finishing destroying the whole range. Upon successful
+ * completion, 0 is returned.
+ */
+static inline int s390_uv_destroy_range_interruptible(struct mm_struct *mm, unsigned long start,
+						      unsigned long end)
+{
+	return __s390_uv_destroy_range(mm, start, end, true);
+}
 #endif /* _ASM_S390_GMAP_H */
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 3c59ef763dde..2ab22500e092 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -12,6 +12,8 @@
 #include <asm/gmap.h>
 #include <asm/uv.h>
 #include <asm/mman.h>
+#include <linux/pagewalk.h>
+#include <linux/sched/mm.h>
 #include "kvm-s390.h"
 
 int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc)
@@ -157,8 +159,14 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 {
 	int cc;
 
-	/* make all pages accessible before destroying the guest */
-	s390_reset_acc(kvm->mm);
+	/*
+	 * if the mm still has a mapping, make all its pages accessible
+	 * before destroying the guest
+	 */
+	if (mmget_not_zero(kvm->mm)) {
+		s390_uv_destroy_range(kvm->mm, 0, TASK_SIZE);
+		mmput(kvm->mm);
+	}
 
 	cc = uv_cmd_nodata(kvm_s390_pv_get_handle(kvm),
 			   UVC_CMD_DESTROY_SEC_CONF, rc, rrc);
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 3b42bf7adb77..f6a80f139b84 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2676,44 +2676,81 @@ void s390_reset_cmma(struct mm_struct *mm)
 }
 EXPORT_SYMBOL_GPL(s390_reset_cmma);
 
-/*
- * make inaccessible pages accessible again
- */
-static int __s390_reset_acc(pte_t *ptep, unsigned long addr,
-			    unsigned long next, struct mm_walk *walk)
+#define DESTROY_LOOP_THRESHOLD 32
+
+struct reset_walk_state {
+	unsigned long next;
+	unsigned long count;
+	unsigned long pfns[DESTROY_LOOP_THRESHOLD];
+};
+
+static int s390_gather_pages(pte_t *ptep, unsigned long addr,
+			     unsigned long next, struct mm_walk *walk)
 {
+	struct reset_walk_state *p = walk->private;
 	pte_t pte = READ_ONCE(*ptep);
 
-	/* There is a reference through the mapping */
-	if (pte_present(pte))
-		WARN_ON_ONCE(uv_destroy_owned_page(pte_val(pte) & PAGE_MASK));
-
-	return 0;
+	if (pte_present(pte)) {
+		/* we have a reference from the mapping, take an extra one */
+		get_page(phys_to_page(pte_val(pte)));
+		p->pfns[p->count] = phys_to_pfn(pte_val(pte));
+		p->next = next;
+		p->count++;
+	}
+	return p->count >= DESTROY_LOOP_THRESHOLD;
 }
 
-static const struct mm_walk_ops reset_acc_walk_ops = {
-	.pte_entry		= __s390_reset_acc,
+static const struct mm_walk_ops gather_pages_ops = {
+	.pte_entry = s390_gather_pages,
 };
 
-#include <linux/sched/mm.h>
-void s390_reset_acc(struct mm_struct *mm)
+/*
+ * Call the Destroy secure page UVC on each page in the given array of PFNs.
+ * Each page needs to have an extra reference, which will be released here.
+ */
+void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns)
 {
-	if (!mm_is_protected(mm))
-		return;
-	/*
-	 * we might be called during
-	 * reset:                             we walk the pages and clear
-	 * close of all kvm file descriptors: we walk the pages and clear
-	 * exit of process on fd closure:     vma already gone, do nothing
-	 */
-	if (!mmget_not_zero(mm))
-		return;
-	mmap_read_lock(mm);
-	walk_page_range(mm, 0, TASK_SIZE, &reset_acc_walk_ops, NULL);
-	mmap_read_unlock(mm);
-	mmput(mm);
+	unsigned long i;
+
+	for (i = 0; i < count; i++) {
+		/* we always have an extra reference */
+		uv_destroy_owned_page(pfn_to_phys(pfns[i]));
+		/* get rid of the extra reference */
+		put_page(pfn_to_page(pfns[i]));
+		cond_resched();
+	}
+}
+EXPORT_SYMBOL_GPL(s390_uv_destroy_pfns);
+
+/**
+ * __s390_uv_destroy_range - Walk the given range of the given address
+ * space, and call the destroy secure page UVC on each page.
+ * Optionally exit early if a fatal signal is pending.
+ * @mm the mm to operate on
+ * @start the start of the range
+ * @end the end of the range
+ * @interruptible if not 0, stop when a fatal signal is received
+ * Return: 0 on success, -EINTR if the function stopped before completing
+ */
+int __s390_uv_destroy_range(struct mm_struct *mm, unsigned long start,
+			    unsigned long end, bool interruptible)
+{
+	struct reset_walk_state state = { .next = start };
+	int r = 1;
+
+	while (r > 0) {
+		state.count = 0;
+		mmap_read_lock(mm);
+		r = walk_page_range(mm, state.next, end, &gather_pages_ops, &state);
+		mmap_read_unlock(mm);
+		cond_resched();
+		s390_uv_destroy_pfns(state.count, state.pfns);
+		if (interruptible && fatal_signal_pending(current))
+			return -EINTR;
+	}
+	return 0;
 }
-EXPORT_SYMBOL_GPL(s390_reset_acc);
+EXPORT_SYMBOL_GPL(__s390_uv_destroy_range);
 
 /**
  * s390_remove_old_asce - Remove the topmost level of page tables from the
-- 
2.34.1

[PATCH v9 05/18] KVM: s390: pv: usage counter instead of flag

[Claudio Imbrenda]

Use the new protected_count field as a counter instead of the old
is_protected flag. This will be used in upcoming patches.

Increment the counter when a secure configuration is created, and
decrement it when it is destroyed. Previously the flag was set when the
set secure parameters UVC was performed.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
---
 arch/s390/include/asm/mmu.h         |  2 +-
 arch/s390/include/asm/mmu_context.h |  2 +-
 arch/s390/include/asm/pgtable.h     |  2 +-
 arch/s390/kvm/pv.c                  | 12 +++++++-----
 4 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/arch/s390/include/asm/mmu.h b/arch/s390/include/asm/mmu.h
index e12ff0f29d1a..2c4cbc254604 100644
--- a/arch/s390/include/asm/mmu.h
+++ b/arch/s390/include/asm/mmu.h
@@ -17,7 +17,7 @@ typedef struct {
 	unsigned long asce_limit;
 	unsigned long vdso_base;
 	/* The mmu context belongs to a secure guest. */
-	atomic_t is_protected;
+	atomic_t protected_count;
 	/*
 	 * The following bitfields need a down_write on the mm
 	 * semaphore when they are written to. As they are only
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index c7937f369e62..2a38af5a00c2 100644
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -26,7 +26,7 @@ static inline int init_new_context(struct task_struct *tsk,
 	INIT_LIST_HEAD(&mm->context.gmap_list);
 	cpumask_clear(&mm->context.cpu_attach_mask);
 	atomic_set(&mm->context.flush_count, 0);
-	atomic_set(&mm->context.is_protected, 0);
+	atomic_set(&mm->context.protected_count, 0);
 	mm->context.gmap_asce = 0;
 	mm->context.flush_mm = 0;
 #ifdef CONFIG_PGSTE
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 008a6c856fa4..23ca0d8e058a 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -523,7 +523,7 @@ static inline int mm_has_pgste(struct mm_struct *mm)
 static inline int mm_is_protected(struct mm_struct *mm)
 {
 #ifdef CONFIG_PGSTE
-	if (unlikely(atomic_read(&mm->context.is_protected)))
+	if (unlikely(atomic_read(&mm->context.protected_count)))
 		return 1;
 #endif
 	return 0;
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 2ab22500e092..9e900ce7387d 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -171,7 +171,8 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 	cc = uv_cmd_nodata(kvm_s390_pv_get_handle(kvm),
 			   UVC_CMD_DESTROY_SEC_CONF, rc, rrc);
 	WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
-	atomic_set(&kvm->mm->context.is_protected, 0);
+	if (!cc)
+		atomic_dec(&kvm->mm->context.protected_count);
 	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
 	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
 	/* Intended memory leak on "impossible" error */
@@ -213,11 +214,14 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 	/* Outputs */
 	kvm->arch.pv.handle = uvcb.guest_handle;
 
+	atomic_inc(&kvm->mm->context.protected_count);
 	if (cc) {
-		if (uvcb.header.rc & UVC_RC_NEED_DESTROY)
+		if (uvcb.header.rc & UVC_RC_NEED_DESTROY) {
 			kvm_s390_pv_deinit_vm(kvm, &dummy, &dummy);
-		else
+		} else {
+			atomic_dec(&kvm->mm->context.protected_count);
 			kvm_s390_pv_dealloc_vm(kvm);
+		}
 		return -EIO;
 	}
 	kvm->arch.gmap->guest_handle = uvcb.guest_handle;
@@ -240,8 +244,6 @@ int kvm_s390_pv_set_sec_parms(struct kvm *kvm, void *hdr, u64 length, u16 *rc,
 	*rrc = uvcb.header.rrc;
 	KVM_UV_EVENT(kvm, 3, "PROTVIRT VM SET PARMS: rc %x rrc %x",
 		     *rc, *rrc);
-	if (!cc)
-		atomic_set(&kvm->mm->context.is_protected, 1);
 	return cc ? -EINVAL : 0;
 }
 
-- 
2.34.1

[PATCH v9 06/18] KVM: s390: pv: add export before import

[Claudio Imbrenda]

Due to upcoming changes, it will be possible to temporarily have
multiple protected VMs in the same address space, although only one
will be actually active.

In that scenario, it is necessary to perform an export of every page
that is to be imported, since the hardware does not allow a page
belonging to a protected guest to be imported into a different
protected guest.

This also applies to pages that are shared, and thus accessible by the
host.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
---
 arch/s390/kernel/uv.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index 2754471cc789..e358b8bd864b 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -234,6 +234,12 @@ static int make_secure_pte(pte_t *ptep, unsigned long addr,
 	return uvcb->rc == 0x10a ? -ENXIO : -EINVAL;
 }
 
+static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm)
+{
+	return uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
+		atomic_read(&mm->context.protected_count) > 1;
+}
+
 /*
  * Requests the Ultravisor to make a page accessible to a guest.
  * If it's brought in the first time, it will be cleared. If
@@ -277,6 +283,8 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb)
 
 	lock_page(page);
 	ptep = get_locked_pte(gmap->mm, uaddr, &ptelock);
+	if (should_export_before_import(uvcb, gmap->mm))
+		uv_convert_from_secure(page_to_phys(page));
 	rc = make_secure_pte(ptep, uaddr, page, uvcb);
 	pte_unmap_unlock(ptep, ptelock);
 	unlock_page(page);
-- 
2.34.1

[PATCH v9 07/18] KVM: s390: pv: module parameter to fence lazy destroy

[Claudio Imbrenda]

Add the module parameter "lazy_destroy", to allow the asynchronous destroy
mechanism to be switched off. This might be useful for debugging purposes.

The parameter is enabled by default.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
---
 arch/s390/kvm/kvm-s390.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 2296b1ff1e02..702696189505 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -207,6 +207,11 @@ unsigned int diag9c_forwarding_hz;
 module_param(diag9c_forwarding_hz, uint, 0644);
 MODULE_PARM_DESC(diag9c_forwarding_hz, "Maximum diag9c forwarding per second, 0 to turn off");
 
+/* allow asynchronous deinit for protected guests */
+static int lazy_destroy = 1;
+module_param(lazy_destroy, int, 0444);
+MODULE_PARM_DESC(lazy_destroy, "Asynchronous destroy for protected guests");
+
 /*
  * For now we handle at most 16 double words as this is what the s390 base
  * kernel handles and stores in the prefix page. If we ever need to go beyond
-- 
2.34.1

[PATCH v9 08/18] KVM: s390: pv: clear the state without memset

[Claudio Imbrenda]

Do not use memset to clean the whole struct kvm_s390_pv; instead,
explicitly clear the fields that need to be cleared.

Upcoming patches will introduce new fields in the struct kvm_s390_pv
that will not need to be cleared.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
---
 arch/s390/kvm/pv.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 9e900ce7387d..76ef33a277d3 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -16,6 +16,14 @@
 #include <linux/sched/mm.h>
 #include "kvm-s390.h"
 
+static void kvm_s390_clear_pv_state(struct kvm *kvm)
+{
+	kvm->arch.pv.handle = 0;
+	kvm->arch.pv.guest_len = 0;
+	kvm->arch.pv.stor_base = 0;
+	kvm->arch.pv.stor_var = NULL;
+}
+
 int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc)
 {
 	int cc;
@@ -110,7 +118,7 @@ static void kvm_s390_pv_dealloc_vm(struct kvm *kvm)
 	vfree(kvm->arch.pv.stor_var);
 	free_pages(kvm->arch.pv.stor_base,
 		   get_order(uv_info.guest_base_stor_len));
-	memset(&kvm->arch.pv, 0, sizeof(kvm->arch.pv));
+	kvm_s390_clear_pv_state(kvm);
 }
 
 static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
-- 
2.34.1

[PATCH v9 09/18] KVM: s390: pv: Add kvm_s390_cpus_from_pv to kvm-s390.h and add documentation

[Claudio Imbrenda]

Future changes make it necessary to call this function from pv.c.

While we are at it, let's properly document kvm_s390_cpus_from_pv() and
kvm_s390_cpus_to_pv().

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
---
 arch/s390/kvm/kvm-s390.c | 26 +++++++++++++++++++++++++-
 arch/s390/kvm/kvm-s390.h |  1 +
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 702696189505..21fcca09e9bf 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2175,7 +2175,20 @@ static int kvm_s390_set_cmma_bits(struct kvm *kvm,
 	return r;
 }
 
-static int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp)
+/**
+ * kvm_s390_cpus_from_pv - Convert all protected vCPUs in a protected VM to
+ * non protected.
+ * @kvm the VM whose protected vCPUs are to be converted
+ * @rcp return value for the RC field of the UVC (in case of error)
+ * @rrcp return value for the RRC field of the UVC (in case of error)
+ *
+ * Does not stop in case of error, tries to convert as many
+ * CPUs as possible. In case of error, the RC and RRC of the last error are
+ * returned.
+ *
+ * Return: 0 in case of success, otherwise -EIO
+ */
+int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp)
 {
 	struct kvm_vcpu *vcpu;
 	u16 rc, rrc;
@@ -2202,6 +2215,17 @@ static int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp)
 	return ret;
 }
 
+/**
+ * kvm_s390_cpus_to_pv - Convert all non-protected vCPUs in a protected VM
+ * to protected.
+ * @kvm the VM whose protected vCPUs are to be converted
+ * @rcp return value for the RC field of the UVC (in case of error)
+ * @rrcp return value for the RRC field of the UVC (in case of error)
+ *
+ * Tries to undo the conversion in case of error.
+ *
+ * Return: 0 in case of success, otherwise -EIO
+ */
 static int kvm_s390_cpus_to_pv(struct kvm *kvm, u16 *rc, u16 *rrc)
 {
 	unsigned long i;
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 098831e815e6..9276d910631b 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -365,6 +365,7 @@ int kvm_s390_vcpu_setup_cmma(struct kvm_vcpu *vcpu);
 void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu);
 void kvm_s390_set_cpu_timer(struct kvm_vcpu *vcpu, __u64 cputm);
 __u64 kvm_s390_get_cpu_timer(struct kvm_vcpu *vcpu);
+int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp);
 
 /* implemented in diag.c */
 int kvm_s390_handle_diag(struct kvm_vcpu *vcpu);
-- 
2.34.1

[PATCH v9 10/18] KVM: s390: pv: add mmu_notifier

[Claudio Imbrenda]

Add an mmu_notifier for protected VMs. The callback function is
triggered when the mm is torn down, and will attempt to convert all
protected vCPUs to non-protected. This allows the mm teardown to use
the destroy page UVC instead of export.

Also make KVM select CONFIG_MMU_NOTIFIER, needed to use mmu_notifiers.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/include/asm/kvm_host.h |  2 ++
 arch/s390/kvm/Kconfig            |  1 +
 arch/s390/kvm/kvm-s390.c         |  5 ++++-
 arch/s390/kvm/pv.c               | 26 ++++++++++++++++++++++++++
 4 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index a22c9266ea05..1bccb8561ba9 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -19,6 +19,7 @@
 #include <linux/kvm.h>
 #include <linux/seqlock.h>
 #include <linux/module.h>
+#include <linux/mmu_notifier.h>
 #include <asm/debug.h>
 #include <asm/cpu.h>
 #include <asm/fpu/api.h>
@@ -921,6 +922,7 @@ struct kvm_s390_pv {
 	u64 guest_len;
 	unsigned long stor_base;
 	void *stor_var;
+	struct mmu_notifier mmu_notifier;
 };
 
 struct kvm_arch{
diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
index 2e84d3922f7c..33f4ff909476 100644
--- a/arch/s390/kvm/Kconfig
+++ b/arch/s390/kvm/Kconfig
@@ -34,6 +34,7 @@ config KVM
 	select SRCU
 	select KVM_VFIO
 	select INTERVAL_TREE
+	select MMU_NOTIFIER
 	help
 	  Support hosting paravirtualized guest machines using the SIE
 	  virtualization capability on the mainframe. This should work
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 21fcca09e9bf..446f89db93a1 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -32,6 +32,7 @@
 #include <linux/sched/signal.h>
 #include <linux/string.h>
 #include <linux/pgtable.h>
+#include <linux/mmu_notifier.h>
 
 #include <asm/asm-offsets.h>
 #include <asm/lowcore.h>
@@ -2833,8 +2834,10 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
 	 * can mess with the pv state. To avoid lockdep_assert_held from
 	 * complaining we do not use kvm_s390_pv_is_protected.
 	 */
-	if (kvm_s390_pv_get_handle(kvm))
+	if (kvm_s390_pv_get_handle(kvm)) {
 		kvm_s390_pv_deinit_vm(kvm, &rc, &rrc);
+		mmu_notifier_unregister(&kvm->arch.pv.mmu_notifier, kvm->mm);
+	}
 	debug_unregister(kvm->arch.dbf);
 	free_page((unsigned long)kvm->arch.sie_page2);
 	if (!kvm_is_ucontrol(kvm))
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 76ef33a277d3..788b96b36931 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -14,6 +14,7 @@
 #include <asm/mman.h>
 #include <linux/pagewalk.h>
 #include <linux/sched/mm.h>
+#include <linux/mmu_notifier.h>
 #include "kvm-s390.h"
 
 static void kvm_s390_clear_pv_state(struct kvm *kvm)
@@ -192,6 +193,26 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 	return -EIO;
 }
 
+static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
+					     struct mm_struct *mm)
+{
+	struct kvm *kvm = container_of(subscription, struct kvm, arch.pv.mmu_notifier);
+	u16 dummy;
+
+	/*
+	 * No locking is needed since this is the last thread of the last user of this
+	 * struct mm.
+	 * When the struct kvm gets deinitialized, this notifier is also
+	 * unregistered. This means that if this notifier runs, then the
+	 * struct kvm is still valid.
+	 */
+	kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);
+}
+
+static const struct mmu_notifier_ops kvm_s390_pv_mmu_notifier_ops = {
+	.release = kvm_s390_pv_mmu_notifier_release,
+};
+
 int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 {
 	struct uv_cb_cgc uvcb = {
@@ -233,6 +254,11 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 		return -EIO;
 	}
 	kvm->arch.gmap->guest_handle = uvcb.guest_handle;
+	/* Add the notifier only once. No races because we hold kvm->lock */
+	if (kvm->arch.pv.mmu_notifier.ops != &kvm_s390_pv_mmu_notifier_ops) {
+		kvm->arch.pv.mmu_notifier.ops = &kvm_s390_pv_mmu_notifier_ops;
+		mmu_notifier_register(&kvm->arch.pv.mmu_notifier, kvm->mm);
+	}
 	return 0;
 }
 
-- 
2.34.1

[PATCH v9 11/18] s390/mm: KVM: pv: when tearing down, try to destroy protected pages

[Claudio Imbrenda]

When ptep_get_and_clear_full is called for a mm teardown, we will now
attempt to destroy the secure pages. This will be faster than export.

In case it was not a teardown, or if for some reason the destroy page
UVC failed, we try with an export page, like before.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
---
 arch/s390/include/asm/pgtable.h | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 23ca0d8e058a..72544a1b4a68 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1118,9 +1118,21 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
 	} else {
 		res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
 	}
-	/* At this point the reference through the mapping is still present */
-	if (mm_is_protected(mm) && pte_present(res))
-		uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
+	/* Nothing to do */
+	if (!mm_is_protected(mm) || !pte_present(res))
+		return res;
+	/*
+	 * At this point the reference through the mapping is still present.
+	 * The notifier should have destroyed all protected vCPUs at this
+	 * point, so the destroy should be successful.
+	 */
+	if (full && !uv_destroy_owned_page(pte_val(res) & PAGE_MASK))
+		return res;
+	/*
+	 * But if something went wrong and the pages could not be destroyed,
+	 * the slower export is used as fallback instead.
+	 */
+	uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
 	return res;
 }
 
-- 
2.34.1

[PATCH v9 12/18] KVM: s390: pv: refactoring of kvm_s390_pv_deinit_vm

[Claudio Imbrenda]

Refactor kvm_s390_pv_deinit_vm to improve readability and simplify the
improvements that are coming in subsequent patches.

No functional change intended.

[note: this can potentially be squashed into the next patch, I factored
it out to simplify the review process]

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
---
 arch/s390/kvm/pv.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 788b96b36931..be3b467f8feb 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -180,17 +180,17 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 	cc = uv_cmd_nodata(kvm_s390_pv_get_handle(kvm),
 			   UVC_CMD_DESTROY_SEC_CONF, rc, rrc);
 	WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
-	if (!cc)
-		atomic_dec(&kvm->mm->context.protected_count);
-	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
-	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
-	/* Intended memory leak on "impossible" error */
 	if (!cc) {
+		atomic_dec(&kvm->mm->context.protected_count);
 		kvm_s390_pv_dealloc_vm(kvm);
-		return 0;
+	} else {
+		/* Intended memory leak on "impossible" error */
+		s390_replace_asce(kvm->arch.gmap);
 	}
-	s390_replace_asce(kvm->arch.gmap);
-	return -EIO;
+	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
+	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
+
+	return cc ? -EIO : 0;
 }
 
 static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
-- 
2.34.1

[PATCH v9 13/18] KVM: s390: pv: cleanup leftover protected VMs if needed

[Claudio Imbrenda]

In upcoming patches it will be possible to start tearing down a
protected VM, and finish the teardown concurrently in a different
thread.

Protected VMs that are pending for tear down ("leftover") need to be
cleaned properly when the userspace process (e.g. qemu) terminates.

This patch makes sure that all "leftover" protected VMs are always
properly torn down.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/include/asm/kvm_host.h |  2 +
 arch/s390/kvm/kvm-s390.c         |  1 +
 arch/s390/kvm/pv.c               | 69 ++++++++++++++++++++++++++++++++
 3 files changed, 72 insertions(+)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 1bccb8561ba9..50e3516cbc03 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -922,6 +922,8 @@ struct kvm_s390_pv {
 	u64 guest_len;
 	unsigned long stor_base;
 	void *stor_var;
+	void *async_deinit;
+	struct list_head need_cleanup;
 	struct mmu_notifier mmu_notifier;
 };
 
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 446f89db93a1..3637f556ff33 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2788,6 +2788,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	kvm_s390_vsie_init(kvm);
 	if (use_gisa)
 		kvm_s390_gisa_init(kvm);
+	INIT_LIST_HEAD(&kvm->arch.pv.need_cleanup);
 	KVM_EVENT(3, "vm 0x%pK created by pid %u", kvm, current->pid);
 
 	return 0;
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index be3b467f8feb..56412617dd01 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -17,6 +17,19 @@
 #include <linux/mmu_notifier.h>
 #include "kvm-s390.h"
 
+/**
+ * @struct deferred_priv
+ * Represents a "leftover" protected VM that does not correspond to any
+ * active KVM VM.
+ */
+struct deferred_priv {
+	struct list_head list;
+	unsigned long old_table;
+	u64 handle;
+	void *stor_var;
+	unsigned long stor_base;
+};
+
 static void kvm_s390_clear_pv_state(struct kvm *kvm)
 {
 	kvm->arch.pv.handle = 0;
@@ -163,6 +176,60 @@ static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
 	return -ENOMEM;
 }
 
+/**
+ * kvm_s390_pv_cleanup_deferred - Clean up one leftover protected VM.
+ * @kvm the KVM that was associated with this leftover protected VM
+ * @deferred details about the leftover protected VM that needs a clean up
+ * Return: 0 in case of success, otherwise 1
+ */
+static int kvm_s390_pv_cleanup_deferred(struct kvm *kvm, struct deferred_priv *deferred)
+{
+	u16 rc, rrc;
+	int cc;
+
+	cc = uv_cmd_nodata(deferred->handle, UVC_CMD_DESTROY_SEC_CONF, &rc, &rrc);
+	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", rc, rrc);
+	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", rc, rrc);
+	if (cc)
+		return cc;
+	/*
+	 * Intentionally leak unusable memory. If the UVC fails, the memory
+	 * used for the VM and its metadata is permanently unusable.
+	 * This can only happen in case of a serious KVM or hardware bug; it
+	 * is not expected to happen in normal operation.
+	 */
+	free_pages(deferred->stor_base, get_order(uv_info.guest_base_stor_len));
+	free_pages(deferred->old_table, CRST_ALLOC_ORDER);
+	vfree(deferred->stor_var);
+	return 0;
+}
+
+/**
+ * kvm_s390_pv_cleanup_leftovers - Clean up all leftover protected VMs.
+ * @kvm the KVM whose leftover protected VMs are to be cleaned up
+ * Return: 0 in case of success, otherwise 1
+ */
+static int kvm_s390_pv_cleanup_leftovers(struct kvm *kvm)
+{
+	struct deferred_priv *deferred;
+	int cc = 0;
+
+	if (kvm->arch.pv.async_deinit)
+		list_add(kvm->arch.pv.async_deinit, &kvm->arch.pv.need_cleanup);
+
+	while (!list_empty(&kvm->arch.pv.need_cleanup)) {
+		deferred = list_first_entry(&kvm->arch.pv.need_cleanup, typeof(*deferred), list);
+		if (kvm_s390_pv_cleanup_deferred(kvm, deferred))
+			cc = 1;
+		else
+			atomic_dec(&kvm->mm->context.protected_count);
+		list_del(&deferred->list);
+		kfree(deferred);
+	}
+	kvm->arch.pv.async_deinit = NULL;
+	return cc;
+}
+
 /* this should not fail, but if it does, we must not free the donated memory */
 int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 {
@@ -190,6 +257,8 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
 	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
 
+	cc |= kvm_s390_pv_cleanup_leftovers(kvm);
+
 	return cc ? -EIO : 0;
 }
 
-- 
2.34.1

[PATCH v9 14/18] KVM: s390: pv: asynchronous destroy for reboot

[Claudio Imbrenda]

Until now, destroying a protected guest was an entirely synchronous
operation that could potentially take a very long time, depending on
the size of the guest, due to the time needed to clean up the address
space from protected pages.

This patch implements an asynchronous destroy mechanism, that allows a
protected guest to reboot significantly faster than previously.

This is achieved by clearing the pages of the old guest in background.
In case of reboot, the new guest will be able to run in the same
address space almost immediately.

The old protected guest is then only destroyed when all of its memory has
been destroyed or otherwise made non protected.

Two new PV commands are added for the KVM_S390_PV_COMMAND ioctl:

KVM_PV_ASYNC_DISABLE_PREPARE: prepares the current protected VM for
asynchronous teardown. The current VM will then continue immediately
as non-protected. If a protected VM had already been set aside without
starting the teardown process, this call will fail.

KVM_PV_ASYNC_DISABLE: tears down the protected VM previously set aside
for asynchronous teardown. This PV command should ideally be issued by
userspace from a separate thread. If a fatal signal is received (or the
process terminates naturally), the command will terminate immediately
without completing.

Leftover protected VMs are cleaned up when a KVM VM is torn down
normally (either via IOCTL or when the process terminates); this
cleanup has been implemented in a previous patch.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/kvm/kvm-s390.c |  24 ++++++++
 arch/s390/kvm/kvm-s390.h |   2 +
 arch/s390/kvm/pv.c       | 126 +++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/kvm.h |   2 +
 4 files changed, 154 insertions(+)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 3637f556ff33..2453d2d90d6c 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2285,6 +2285,30 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
 		set_bit(IRQ_PEND_EXT_SERVICE, &kvm->arch.float_int.masked_irqs);
 		break;
 	}
+	case KVM_PV_ASYNC_DISABLE_PREPARE:
+		r = -EINVAL;
+		if (!kvm_s390_pv_is_protected(kvm) || !lazy_destroy)
+			break;
+
+		r = kvm_s390_cpus_from_pv(kvm, &cmd->rc, &cmd->rrc);
+		/*
+		 * If a CPU could not be destroyed, destroy VM will also fail.
+		 * There is no point in trying to destroy it. Instead return
+		 * the rc and rrc from the first CPU that failed destroying.
+		 */
+		if (r)
+			break;
+		r = kvm_s390_pv_deinit_vm_async_prepare(kvm, &cmd->rc, &cmd->rrc);
+
+		/* no need to block service interrupts any more */
+		clear_bit(IRQ_PEND_EXT_SERVICE, &kvm->arch.float_int.masked_irqs);
+		break;
+	case KVM_PV_ASYNC_DISABLE:
+		r = -EINVAL;
+		if (!kvm->arch.pv.async_deinit)
+			break;
+		r = kvm_s390_pv_deinit_vm_async(kvm, &cmd->rc, &cmd->rrc);
+		break;
 	case KVM_PV_DISABLE: {
 		r = -EINVAL;
 		if (!kvm_s390_pv_is_protected(kvm))
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 9276d910631b..be53c7750248 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -234,6 +234,8 @@ static inline unsigned long kvm_s390_get_gfn_end(struct kvm_memslots *slots)
 /* implemented in pv.c */
 int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc);
 int kvm_s390_pv_create_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc);
+int kvm_s390_pv_deinit_vm_async_prepare(struct kvm *kvm, u16 *rc, u16 *rrc);
+int kvm_s390_pv_deinit_vm_async(struct kvm *kvm, u16 *rc, u16 *rrc);
 int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc);
 int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc);
 int kvm_s390_pv_set_sec_parms(struct kvm *kvm, void *hdr, u64 length, u16 *rc,
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 56412617dd01..5111f1fc64ab 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -262,6 +262,132 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 	return cc ? -EIO : 0;
 }
 
+/**
+ * kvm_s390_clear_2g - Clear the first 2GB of guest memory.
+ * @kvm the VM whose memory is to be cleared.
+ * Clear the first 2GB of guest memory, to avoid prefix issues after reboot.
+ */
+static void kvm_s390_clear_2g(struct kvm *kvm)
+{
+	struct kvm_memory_slot *slot;
+	unsigned long lim;
+	int srcu_idx;
+
+	srcu_idx = srcu_read_lock(&kvm->srcu);
+
+	slot = gfn_to_memslot(kvm, 0);
+	/* Clear all slots that are completely below 2GB */
+	while (slot && slot->base_gfn + slot->npages < SZ_2G / PAGE_SIZE) {
+		lim = slot->userspace_addr + slot->npages * PAGE_SIZE;
+		s390_uv_destroy_range(kvm->mm, slot->userspace_addr, lim);
+		slot = gfn_to_memslot(kvm, slot->base_gfn + slot->npages);
+	}
+	/* Last slot crosses the 2G boundary, clear only up to 2GB */
+	if (slot && slot->base_gfn < SZ_2G / PAGE_SIZE) {
+		lim = slot->userspace_addr + SZ_2G - slot->base_gfn * PAGE_SIZE;
+		s390_uv_destroy_range(kvm->mm, slot->userspace_addr, lim);
+	}
+
+	srcu_read_unlock(&kvm->srcu, srcu_idx);
+}
+
+/**
+ * kvm_s390_pv_deinit_vm_async_prepare - Prepare a protected VM for
+ * asynchronous teardown.
+ * @kvm the VM
+ * @rc return value for the RC field of the UVCB
+ * @rrc return value for the RRC field of the UVCB
+ *
+ * Prepare the protected VM for asynchronous teardown. The VM will be able
+ * to continue immediately as a non-secure VM, and the information needed to
+ * properly tear down the protected VM is set aside. If another protected VM
+ * was already set aside without starting a teardown, the function will
+ * fail.
+ *
+ * Context: kvm->lock needs to be held
+ *
+ * Return: 0 in case of success, -EINVAL if another protected VM was already set
+ * aside, -ENOMEM if the system ran out of memory.
+ */
+int kvm_s390_pv_deinit_vm_async_prepare(struct kvm *kvm, u16 *rc, u16 *rrc)
+{
+	struct deferred_priv *priv;
+
+	/*
+	 * If an asynchronous deinitialization is already pending, refuse.
+	 * A synchronous deinitialization has to be performed instead.
+	 */
+	if (kvm->arch.pv.async_deinit)
+		return -EINVAL;
+	priv = kmalloc(sizeof(*priv), GFP_KERNEL | __GFP_ZERO);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->stor_var = kvm->arch.pv.stor_var;
+	priv->stor_base = kvm->arch.pv.stor_base;
+	priv->handle = kvm_s390_pv_get_handle(kvm);
+	priv->old_table = (unsigned long)kvm->arch.gmap->table;
+	WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
+	if (s390_replace_asce(kvm->arch.gmap)) {
+		kfree(priv);
+		return -ENOMEM;
+	}
+
+	kvm_s390_clear_2g(kvm);
+	kvm_s390_clear_pv_state(kvm);
+	kvm->arch.pv.async_deinit = priv;
+
+	*rc = 1;
+	*rrc = 42;
+	return 0;
+}
+
+/**
+ * kvm_s390_pv_deinit_vm_async - Perform an asynchronous teardown of a
+ * protected VM.
+ * @kvm the VM previously associated with the protected VM
+ * @rc return value for the RC field of the UVCB
+ * @rrc return value for the RRC field of the UVCB
+ *
+ * Tear down the protected VM that had previously been set aside using
+ * kvm_s390_pv_deinit_vm_async_prepare.
+ *
+ * Context: kvm->lock needs to be held
+ *
+ * Return: 0 in case of success, -EINVAL if no protected VM had been
+ * prepared for asynchronous teardowm, -EIO in case of other errors.
+ */
+int kvm_s390_pv_deinit_vm_async(struct kvm *kvm, u16 *rc, u16 *rrc)
+{
+	struct deferred_priv *p = kvm->arch.pv.async_deinit;
+	int ret = 0;
+
+	if (!p)
+		return -EINVAL;
+	kvm->arch.pv.async_deinit = NULL;
+	mutex_unlock(&kvm->lock);
+
+	/* When a fatal signal is received, stop immediately */
+	if (s390_uv_destroy_range_interruptible(kvm->mm, 0, TASK_SIZE_MAX))
+		goto done;
+	if (kvm_s390_pv_cleanup_deferred(kvm, p))
+		ret = -EIO;
+	else
+		atomic_dec(&kvm->mm->context.protected_count);
+	kfree(p);
+	p = NULL;
+done:
+	/* The caller expects the lock to be held */
+	mutex_lock(&kvm->lock);
+	/*
+	 * p is not NULL if we aborted because of a fatal signal, in which
+	 * case queue the leftover for later cleanup.
+	 */
+	if (p)
+		list_add(&p->list, &kvm->arch.pv.need_cleanup);
+	return ret;
+}
+
 static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
 					     struct mm_struct *mm)
 {
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 507ee1f2aa96..d150610e7a4b 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1644,6 +1644,8 @@ enum pv_cmd_id {
 	KVM_PV_VERIFY,
 	KVM_PV_PREP_RESET,
 	KVM_PV_UNSHARE_ALL,
+	KVM_PV_ASYNC_DISABLE_PREPARE,
+	KVM_PV_ASYNC_DISABLE,
 };
 
 struct kvm_pv_cmd {
-- 
2.34.1

[PATCH v9 15/18] KVM: s390: pv: api documentation for asynchronous destroy

[Claudio Imbrenda]

Add documentation for the new commands added to the KVM_S390_PV_COMMAND
ioctl.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 Documentation/virt/kvm/api.rst | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 9f3172376ec3..52ba1c52ae3c 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5010,11 +5010,13 @@ KVM_PV_ENABLE
   =====      =============================
 
 KVM_PV_DISABLE
-
   Deregister the VM from the Ultravisor and reclaim the memory that
   had been donated to the Ultravisor, making it usable by the kernel
-  again.  All registered VCPUs are converted back to non-protected
-  ones.
+  again. All registered VCPUs are converted back to non-protected
+  ones. If a previous VM had been prepared for asynchonous teardown
+  with KVM_PV_ASYNC_DISABLE_PREPARE and not actually torn down with
+  KVM_PV_ASYNC_DISABLE, it will be torn down in this call together with
+  the current VM.
 
 KVM_PV_VM_SET_SEC_PARMS
   Pass the image header from VM memory to the Ultravisor in
@@ -5027,6 +5029,23 @@ KVM_PV_VM_VERIFY
   Verify the integrity of the unpacked image. Only if this succeeds,
   KVM is allowed to start protected VCPUs.
 
+KVM_PV_ASYNC_DISABLE_PREPARE
+  Prepare the current protected VM for asynchronous teardown. Most
+  resources used by the current protected VM will be set aside for a
+  subsequent asynchronous teardown. The current protected VM will then
+  resume execution immediately as non-protected. If a protected VM had
+  already been prepared without starting the asynchronous teardown process,
+  this call will fail. In that case, the userspace process should issue a
+  normal KVM_PV_DISABLE.
+
+KVM_PV_ASYNC_DISABLE
+  Tear down the protected VM previously prepared for asynchronous teardown.
+  The resources that had been set aside will be freed asynchronously during
+  the execution of this command.
+  This PV command should ideally be issued by userspace from a separate
+  thread. If a fatal signal is received (or the process terminates
+  naturally), the command will terminate immediately without completing.
+
 4.126 KVM_X86_SET_MSR_FILTER
 ----------------------------
 
-- 
2.34.1

[PATCH v9 16/18] KVM: s390: pv: add KVM_CAP_S390_PROTECTED_ASYNC_DISABLE

[Claudio Imbrenda]

Add KVM_CAP_S390_PROTECTED_ASYNC_DISABLE to signal that the
KVM_PV_ASYNC_DISABLE and KVM_PV_ASYNC_DISABLE_PREPARE commands for the
KVM_S390_PV_COMMAND ioctl are available.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/kvm/kvm-s390.c | 3 +++
 include/uapi/linux/kvm.h | 1 +
 2 files changed, 4 insertions(+)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 2453d2d90d6c..8ee143c9a03b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -609,6 +609,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_S390_BPB:
 		r = test_facility(82);
 		break;
+	case KVM_CAP_S390_PROTECTED_ASYNC_DISABLE:
+		r = lazy_destroy && is_prot_virt_host();
+		break;
 	case KVM_CAP_S390_PROTECTED:
 		r = is_prot_virt_host();
 		break;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index d150610e7a4b..d775e891dd39 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1135,6 +1135,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_XSAVE2 208
 #define KVM_CAP_SYS_ATTRIBUTES 209
 #define KVM_CAP_PPC_AIL_MODE_3 210
+#define KVM_CAP_S390_PROTECTED_ASYNC_DISABLE 215
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.34.1

[PATCH v9 17/18] KVM: s390: pv: avoid export before import if possible

[Claudio Imbrenda]

If the appropriate UV feature bit is set, there is no need to perform
an export before import.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/kernel/uv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index e358b8bd864b..43393568f844 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -236,7 +236,8 @@ static int make_secure_pte(pte_t *ptep, unsigned long addr,
 
 static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm)
 {
-	return uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
+	return !test_bit_inv(BIT_UV_FEAT_MISC, &uv_info.uv_feature_indications) &&
+		uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
 		atomic_read(&mm->context.protected_count) > 1;
 }
 
-- 
2.34.1

[PATCH v9 18/18] KVM: s390: pv: support for Destroy fast UVC

[Claudio Imbrenda]

Add support for the Destroy Secure Configuration Fast Ultravisor call,
and take advantage of it for asynchronous destroy.

When supported, the protected guest is destroyed immediately using the
new UVC, leaving only the memory to be cleaned up asynchronously.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/include/asm/uv.h | 10 +++++++
 arch/s390/kvm/pv.c         | 57 ++++++++++++++++++++++++++++++++------
 2 files changed, 58 insertions(+), 9 deletions(-)

diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
index 6b2b33f19abe..b48334565415 100644
--- a/arch/s390/include/asm/uv.h
+++ b/arch/s390/include/asm/uv.h
@@ -34,6 +34,7 @@
 #define UVC_CMD_INIT_UV			0x000f
 #define UVC_CMD_CREATE_SEC_CONF		0x0100
 #define UVC_CMD_DESTROY_SEC_CONF	0x0101
+#define UVC_CMD_DESTROY_SEC_CONF_FAST	0x0102
 #define UVC_CMD_CREATE_SEC_CPU		0x0120
 #define UVC_CMD_DESTROY_SEC_CPU		0x0121
 #define UVC_CMD_CONV_TO_SEC_STOR	0x0200
@@ -76,6 +77,7 @@ enum uv_cmds_inst {
 	BIT_UVC_CMD_UNSHARE_ALL = 20,
 	BIT_UVC_CMD_PIN_PAGE_SHARED = 21,
 	BIT_UVC_CMD_UNPIN_PAGE_SHARED = 22,
+	BIT_UVC_CMD_DESTROY_SEC_CONF_FAST = 23,
 };
 
 enum uv_feat_ind {
@@ -210,6 +212,14 @@ struct uv_cb_nodata {
 	u64 reserved20[4];
 } __packed __aligned(8);
 
+/* Destroy Configuration Fast */
+struct uv_cb_destroy_fast {
+	struct uv_cb_header header;
+	u64 reserved08[2];
+	u64 handle;
+	u64 reserved20[5];
+} __packed __aligned(8);
+
 /* Set Shared Access */
 struct uv_cb_share {
 	struct uv_cb_header header;
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 5111f1fc64ab..4ecc5658fa9a 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -187,6 +187,9 @@ static int kvm_s390_pv_cleanup_deferred(struct kvm *kvm, struct deferred_priv *d
 	u16 rc, rrc;
 	int cc;
 
+	/* It used the destroy-fast UVC, nothing left to do here */
+	if (!deferred->handle)
+		return 0;
 	cc = uv_cmd_nodata(deferred->handle, UVC_CMD_DESTROY_SEC_CONF, &rc, &rrc);
 	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", rc, rrc);
 	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", rc, rrc);
@@ -291,6 +294,32 @@ static void kvm_s390_clear_2g(struct kvm *kvm)
 	srcu_read_unlock(&kvm->srcu, srcu_idx);
 }
 
+static int kvm_s390_pv_deinit_vm_fast(struct kvm *kvm, u16 *rc, u16 *rrc)
+{
+	struct uv_cb_destroy_fast uvcb = {
+		.header.cmd = UVC_CMD_DESTROY_SEC_CONF_FAST,
+		.header.len = sizeof(uvcb),
+		.handle = kvm_s390_pv_get_handle(kvm),
+	};
+	int cc;
+
+	cc = uv_call_sched(0, (u64)&uvcb);
+	*rc = uvcb.header.rc;
+	*rrc = uvcb.header.rrc;
+	WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
+	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM FAST: rc %x rrc %x", *rc, *rrc);
+	WARN_ONCE(cc, "protvirt destroy vm fast failed rc %x rrc %x", *rc, *rrc);
+	/* Inteded memory leak on "impossible" error */
+	if (!cc)
+		kvm_s390_pv_dealloc_vm(kvm);
+	return cc ? -EIO : 0;
+}
+
+static inline bool is_destroy_fast_available(void)
+{
+	return test_bit_inv(BIT_UVC_CMD_DESTROY_SEC_CONF_FAST, uv_info.inst_calls_list);
+}
+
 /**
  * kvm_s390_pv_deinit_vm_async_prepare - Prepare a protected VM for
  * asynchronous teardown.
@@ -312,6 +341,7 @@ static void kvm_s390_clear_2g(struct kvm *kvm)
 int kvm_s390_pv_deinit_vm_async_prepare(struct kvm *kvm, u16 *rc, u16 *rrc)
 {
 	struct deferred_priv *priv;
+	int res;
 
 	/*
 	 * If an asynchronous deinitialization is already pending, refuse.
@@ -323,14 +353,20 @@ int kvm_s390_pv_deinit_vm_async_prepare(struct kvm *kvm, u16 *rc, u16 *rrc)
 	if (!priv)
 		return -ENOMEM;
 
-	priv->stor_var = kvm->arch.pv.stor_var;
-	priv->stor_base = kvm->arch.pv.stor_base;
-	priv->handle = kvm_s390_pv_get_handle(kvm);
-	priv->old_table = (unsigned long)kvm->arch.gmap->table;
-	WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
-	if (s390_replace_asce(kvm->arch.gmap)) {
-		kfree(priv);
-		return -ENOMEM;
+	if (is_destroy_fast_available()) {
+		res = kvm_s390_pv_deinit_vm_fast(kvm, rc, rrc);
+		if (res)
+			return res;
+	} else {
+		priv->stor_var = kvm->arch.pv.stor_var;
+		priv->stor_base = kvm->arch.pv.stor_base;
+		priv->handle = kvm_s390_pv_get_handle(kvm);
+		priv->old_table = (unsigned long)kvm->arch.gmap->table;
+		WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
+		if (s390_replace_asce(kvm->arch.gmap)) {
+			kfree(priv);
+			return -ENOMEM;
+		}
 	}
 
 	kvm_s390_clear_2g(kvm);
@@ -393,6 +429,7 @@ static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
 {
 	struct kvm *kvm = container_of(subscription, struct kvm, arch.pv.mmu_notifier);
 	u16 dummy;
+	int r;
 
 	/*
 	 * No locking is needed since this is the last thread of the last user of this
@@ -401,7 +438,9 @@ static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
 	 * unregistered. This means that if this notifier runs, then the
 	 * struct kvm is still valid.
 	 */
-	kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);
+	r = kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);
+	if (!r)
+		kvm_s390_pv_deinit_vm_fast(kvm, &dummy, &dummy);
 }
 
 static const struct mmu_notifier_ops kvm_s390_pv_mmu_notifier_ops = {
-- 
2.34.1

Re: [PATCH v9 01/18] KVM: s390: pv: leak the topmost page table when destroy fails

[Janosch Frank]

On 3/30/22 14:25, Claudio Imbrenda wrote:
> Each secure guest must have a unique ASCE (address space control
> element); we must avoid that new guests use the same page for their
> ASCE, to avoid errors.
> 
> Since the ASCE mostly consists of the address of the topmost page table
> (plus some flags), we must not return that memory to the pool unless
> the ASCE is no longer in use.
> 
> Only a successful Destroy Secure Configuration UVC will make the ASCE
> reusable again.
> 
> If the Destroy Configuration UVC fails, the ASCE cannot be reused for a
> secure guest (either for the ASCE or for other memory areas). To avoid
> a collision, it must not be used again. This is a permanent error and
> the page becomes in practice unusable, so we set it aside and leak it.
> On failure we already leak other memory that belongs to the ultravisor
> (i.e. the variable and base storage for a guest) and not leaking the
> topmost page table was an oversight.
> 
> This error (and thus the leakage) should not happen unless the hardware
> is broken or KVM has some unknown serious bug.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Fixes: 29b40f105ec8d55 ("KVM: s390: protvirt: Add initial vm and cpu lifecycle handling")
> ---
>   arch/s390/include/asm/gmap.h |  2 +
>   arch/s390/kvm/pv.c           |  9 +++--
>   arch/s390/mm/gmap.c          | 71 ++++++++++++++++++++++++++++++++++++
>   3 files changed, 79 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
> index 40264f60b0da..746e18bf8984 100644
> --- a/arch/s390/include/asm/gmap.h
> +++ b/arch/s390/include/asm/gmap.h
> @@ -148,4 +148,6 @@ void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long dirty_bitmap[4],
>   			     unsigned long gaddr, unsigned long vmaddr);
>   int gmap_mark_unmergeable(void);
>   void s390_reset_acc(struct mm_struct *mm);
> +void s390_remove_old_asce(struct gmap *gmap);
> +int s390_replace_asce(struct gmap *gmap);
>   #endif /* _ASM_S390_GMAP_H */
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index 7f7c0d6af2ce..3c59ef763dde 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -166,10 +166,13 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
>   	atomic_set(&kvm->mm->context.is_protected, 0);
>   	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
>   	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
> -	/* Inteded memory leak on "impossible" error */
> -	if (!cc)
> +	/* Intended memory leak on "impossible" error */
> +	if (!cc) {
>   		kvm_s390_pv_dealloc_vm(kvm);
> -	return cc ? -EIO : 0;
> +		return 0;
> +	}
> +	s390_replace_asce(kvm->arch.gmap);
> +	return -EIO;
>   }
>   
>   int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index dfee0ebb2fac..3b42bf7adb77 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -2714,3 +2714,74 @@ void s390_reset_acc(struct mm_struct *mm)
>   	mmput(mm);
>   }
>   EXPORT_SYMBOL_GPL(s390_reset_acc);
> +
> +/**
> + * s390_remove_old_asce - Remove the topmost level of page tables from the
> + * list of page tables of the gmap.
> + * @gmap the gmap whose table is to be removed
> + *
> + * This means that it will not be freed when the VM is torn down, and needs
> + * to be handled separately by the caller, unless an intentional leak is
> + * intended. Notice that this function will only remove the page from the
> + * list, the page will still be used as a top level page table (and ASCE).
> + */
> +void s390_remove_old_asce(struct gmap *gmap)
> +{
> +	struct page *old;
> +
> +	old = virt_to_page(gmap->table);
> +	spin_lock(&gmap->guest_table_lock);
> +	list_del(&old->lru);
> +	/*
> +	 * in case the ASCE needs to be "removed" multiple times, for example
> +	 * if the VM is rebooted into secure mode several times
> +	 * concurrently.
> +	 */

How can that happen, what are we protecting against here?

> +	INIT_LIST_HEAD(&old->lru);
> +	spin_unlock(&gmap->guest_table_lock);
> +}
> +EXPORT_SYMBOL_GPL(s390_remove_old_asce);
> +
> +/**
> + * s390_replace_asce - Try to replace the current ASCE of a gmap with
> + * another equivalent one.
> + * @gmap the gmap
> + *
> + * If the allocation of the new top level page table fails, the ASCE is not
> + * replaced.
> + * In any case, the old ASCE is always removed from the list. Therefore the
> + * caller has to make sure to save a pointer to it beforehands, unless an
> + * intentional leak is intended.
> + */
> +int s390_replace_asce(struct gmap *gmap)
> +{
> +	unsigned long asce;
> +	struct page *page;
> +	void *table;
> +
> +	s390_remove_old_asce(gmap);
> +
> +	page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
> +	if (!page)
> +		return -ENOMEM;
> +	table = page_to_virt(page);
> +	memcpy(table, gmap->table, 1UL << (CRST_ALLOC_ORDER + PAGE_SHIFT));
> +
> +	/*
> +	 * The caller has to deal with the old ASCE, but here we make sure
> +	 * the new one is properly added to the list of page tables, so that
> +	 * it will be freed when the VM is torn down.
> +	 */
> +	spin_lock(&gmap->guest_table_lock);
> +	list_add(&page->lru, &gmap->crst_list);
> +	spin_unlock(&gmap->guest_table_lock);
> +
> +	/* Set new table origin while preserving existing ASCE control bits */
> +	asce = (gmap->asce & ~_ASCE_ORIGIN) | __pa(table);
> +	WRITE_ONCE(gmap->asce, asce);
> +	WRITE_ONCE(gmap->mm->context.gmap_asce, asce);
> +	WRITE_ONCE(gmap->table, table);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(s390_replace_asce);

Re: [PATCH v9 04/18] KVM: s390: pv: refactor s390_reset_acc

[Janosch Frank]

On 3/30/22 14:25, Claudio Imbrenda wrote:
> Refactor s390_reset_acc so that it can be reused in upcoming patches.
> 
> We don't want to hold all the locks used in a walk_page_range for too
> long, and the destroy page UVC does take some time to complete.
> Therefore we quickly gather the pages to destroy, and then destroy them
> without holding all the locks.
> 
> The new refactored function optionally allows to return early without
> completing if a fatal signal is pending (and return and appropriate
> error code). Two wrappers are provided to call the new function.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> (dropping Janosch's Ack because of major changes to the patch)

Reviewed-by: Janosch Frank <frankja@linux.ibm.com>

[...]
> +#define DESTROY_LOOP_THRESHOLD 32

A question out of curiosity:
Is there any particular reason for the number?
Have you tested other numbers and experienced a speedup/slowdown?

> +
> +struct reset_walk_state {
> +	unsigned long next;
> +	unsigned long count;
> +	unsigned long pfns[DESTROY_LOOP_THRESHOLD];
> +};
> +
> +static int s390_gather_pages(pte_t *ptep, unsigned long addr,
> +			     unsigned long next, struct mm_walk *walk)
>   {
> +	struct reset_walk_state *p = walk->private;
>   	pte_t pte = READ_ONCE(*ptep);
>   
> -	/* There is a reference through the mapping */
> -	if (pte_present(pte))
> -		WARN_ON_ONCE(uv_destroy_owned_page(pte_val(pte) & PAGE_MASK));
> -
> -	return 0;
> +	if (pte_present(pte)) {
> +		/* we have a reference from the mapping, take an extra one */
> +		get_page(phys_to_page(pte_val(pte)));
> +		p->pfns[p->count] = phys_to_pfn(pte_val(pte));
> +		p->next = next;
> +		p->count++;
> +	}
> +	return p->count >= DESTROY_LOOP_THRESHOLD;
>   }
>   
> -static const struct mm_walk_ops reset_acc_walk_ops = {
> -	.pte_entry		= __s390_reset_acc,
> +static const struct mm_walk_ops gather_pages_ops = {
> +	.pte_entry = s390_gather_pages,
>   };
>   
> -#include <linux/sched/mm.h>
> -void s390_reset_acc(struct mm_struct *mm)
> +/*
> + * Call the Destroy secure page UVC on each page in the given array of PFNs.
> + * Each page needs to have an extra reference, which will be released here.
> + */
> +void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns)
>   {
> -	if (!mm_is_protected(mm))
> -		return;
> -	/*
> -	 * we might be called during
> -	 * reset:                             we walk the pages and clear
> -	 * close of all kvm file descriptors: we walk the pages and clear
> -	 * exit of process on fd closure:     vma already gone, do nothing
> -	 */
> -	if (!mmget_not_zero(mm))
> -		return;
> -	mmap_read_lock(mm);
> -	walk_page_range(mm, 0, TASK_SIZE, &reset_acc_walk_ops, NULL);
> -	mmap_read_unlock(mm);
> -	mmput(mm);
> +	unsigned long i;
> +
> +	for (i = 0; i < count; i++) {
> +		/* we always have an extra reference */
> +		uv_destroy_owned_page(pfn_to_phys(pfns[i]));
> +		/* get rid of the extra reference */
> +		put_page(pfn_to_page(pfns[i]));
> +		cond_resched();
> +	}
> +}
> +EXPORT_SYMBOL_GPL(s390_uv_destroy_pfns);
> +
> +/**
> + * __s390_uv_destroy_range - Walk the given range of the given address
> + * space, and call the destroy secure page UVC on each page.
> + * Optionally exit early if a fatal signal is pending.
> + * @mm the mm to operate on
> + * @start the start of the range
> + * @end the end of the range
> + * @interruptible if not 0, stop when a fatal signal is received
> + * Return: 0 on success, -EINTR if the function stopped before completing
> + */
> +int __s390_uv_destroy_range(struct mm_struct *mm, unsigned long start,
> +			    unsigned long end, bool interruptible)
> +{
> +	struct reset_walk_state state = { .next = start };
> +	int r = 1;
> +
> +	while (r > 0) {
> +		state.count = 0;
> +		mmap_read_lock(mm);
> +		r = walk_page_range(mm, state.next, end, &gather_pages_ops, &state);
> +		mmap_read_unlock(mm);
> +		cond_resched();
> +		s390_uv_destroy_pfns(state.count, state.pfns);
> +		if (interruptible && fatal_signal_pending(current))
> +			return -EINTR;
> +	}
> +	return 0;
>   }
> -EXPORT_SYMBOL_GPL(s390_reset_acc);
> +EXPORT_SYMBOL_GPL(__s390_uv_destroy_range);
>   
>   /**
>    * s390_remove_old_asce - Remove the topmost level of page tables from the

Re: [PATCH v9 10/18] KVM: s390: pv: add mmu_notifier

[Janosch Frank]

On 3/30/22 14:25, Claudio Imbrenda wrote:
> Add an mmu_notifier for protected VMs. The callback function is
> triggered when the mm is torn down, and will attempt to convert all
> protected vCPUs to non-protected. This allows the mm teardown to use
> the destroy page UVC instead of export.
> 
> Also make KVM select CONFIG_MMU_NOTIFIER, needed to use mmu_notifiers.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

Acked-by: Janosch Frank <frankja@linux.ibm.com>

> ---
>   arch/s390/include/asm/kvm_host.h |  2 ++
>   arch/s390/kvm/Kconfig            |  1 +
>   arch/s390/kvm/kvm-s390.c         |  5 ++++-
>   arch/s390/kvm/pv.c               | 26 ++++++++++++++++++++++++++
>   4 files changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index a22c9266ea05..1bccb8561ba9 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -19,6 +19,7 @@
>   #include <linux/kvm.h>
>   #include <linux/seqlock.h>
>   #include <linux/module.h>
> +#include <linux/mmu_notifier.h>
>   #include <asm/debug.h>
>   #include <asm/cpu.h>
>   #include <asm/fpu/api.h>
> @@ -921,6 +922,7 @@ struct kvm_s390_pv {
>   	u64 guest_len;
>   	unsigned long stor_base;
>   	void *stor_var;
> +	struct mmu_notifier mmu_notifier;
>   };
>   
>   struct kvm_arch{
> diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
> index 2e84d3922f7c..33f4ff909476 100644
> --- a/arch/s390/kvm/Kconfig
> +++ b/arch/s390/kvm/Kconfig
> @@ -34,6 +34,7 @@ config KVM
>   	select SRCU
>   	select KVM_VFIO
>   	select INTERVAL_TREE
> +	select MMU_NOTIFIER
>   	help
>   	  Support hosting paravirtualized guest machines using the SIE
>   	  virtualization capability on the mainframe. This should work
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 21fcca09e9bf..446f89db93a1 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -32,6 +32,7 @@
>   #include <linux/sched/signal.h>
>   #include <linux/string.h>
>   #include <linux/pgtable.h>
> +#include <linux/mmu_notifier.h>
>   
>   #include <asm/asm-offsets.h>
>   #include <asm/lowcore.h>
> @@ -2833,8 +2834,10 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
>   	 * can mess with the pv state. To avoid lockdep_assert_held from
>   	 * complaining we do not use kvm_s390_pv_is_protected.
>   	 */
> -	if (kvm_s390_pv_get_handle(kvm))
> +	if (kvm_s390_pv_get_handle(kvm)) {
>   		kvm_s390_pv_deinit_vm(kvm, &rc, &rrc);
> +		mmu_notifier_unregister(&kvm->arch.pv.mmu_notifier, kvm->mm);
> +	}
>   	debug_unregister(kvm->arch.dbf);
>   	free_page((unsigned long)kvm->arch.sie_page2);
>   	if (!kvm_is_ucontrol(kvm))
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index 76ef33a277d3..788b96b36931 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -14,6 +14,7 @@
>   #include <asm/mman.h>
>   #include <linux/pagewalk.h>
>   #include <linux/sched/mm.h>
> +#include <linux/mmu_notifier.h>
>   #include "kvm-s390.h"
>   
>   static void kvm_s390_clear_pv_state(struct kvm *kvm)
> @@ -192,6 +193,26 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
>   	return -EIO;
>   }
>   
> +static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
> +					     struct mm_struct *mm)
> +{
> +	struct kvm *kvm = container_of(subscription, struct kvm, arch.pv.mmu_notifier);
> +	u16 dummy;
> +
> +	/*
> +	 * No locking is needed since this is the last thread of the last user of this
> +	 * struct mm.
> +	 * When the struct kvm gets deinitialized, this notifier is also
> +	 * unregistered. This means that if this notifier runs, then the
> +	 * struct kvm is still valid.
> +	 */
> +	kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);
> +}
> +
> +static const struct mmu_notifier_ops kvm_s390_pv_mmu_notifier_ops = {
> +	.release = kvm_s390_pv_mmu_notifier_release,
> +};
> +
>   int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
>   {
>   	struct uv_cb_cgc uvcb = {
> @@ -233,6 +254,11 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
>   		return -EIO;
>   	}
>   	kvm->arch.gmap->guest_handle = uvcb.guest_handle;
> +	/* Add the notifier only once. No races because we hold kvm->lock */
> +	if (kvm->arch.pv.mmu_notifier.ops != &kvm_s390_pv_mmu_notifier_ops) {
> +		kvm->arch.pv.mmu_notifier.ops = &kvm_s390_pv_mmu_notifier_ops;
> +		mmu_notifier_register(&kvm->arch.pv.mmu_notifier, kvm->mm);
> +	}
>   	return 0;
>   }
>   

Re: [PATCH v9 11/18] s390/mm: KVM: pv: when tearing down, try to destroy protected pages

[Janosch Frank]

On 3/30/22 14:25, Claudio Imbrenda wrote:
> When ptep_get_and_clear_full is called for a mm teardown, we will now
> attempt to destroy the secure pages. This will be faster than export.
> 
> In case it was not a teardown, or if for some reason the destroy page
> UVC failed, we try with an export page, like before.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Acked-by: Janosch Frank <frankja@linux.ibm.com>
> ---
>   arch/s390/include/asm/pgtable.h | 18 +++++++++++++++---
>   1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
> index 23ca0d8e058a..72544a1b4a68 100644
> --- a/arch/s390/include/asm/pgtable.h
> +++ b/arch/s390/include/asm/pgtable.h
> @@ -1118,9 +1118,21 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
>   	} else {
>   		res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
>   	}
> -	/* At this point the reference through the mapping is still present */
> -	if (mm_is_protected(mm) && pte_present(res))
> -		uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
> +	/* Nothing to do */
> +	if (!mm_is_protected(mm) || !pte_present(res))
> +		return res;
> +	/*
> +	 * At this point the reference through the mapping is still present.

That's the case because we zap ptes within a mm that's still existing, 
right? The mm will be deleted after we have unmapped the memory.


> +	 * The notifier should have destroyed all protected vCPUs at this
> +	 * point, so the destroy should be successful.
> +	 */
> +	if (full && !uv_destroy_owned_page(pte_val(res) & PAGE_MASK))
> +		return res;
> +	/*
> +	 * But if something went wrong and the pages could not be destroyed,
> +	 * the slower export is used as fallback instead.
> +	 */
> +	uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
>   	return res;
>   }
>   

Re: [PATCH v9 13/18] KVM: s390: pv: cleanup leftover protected VMs if needed

[Janosch Frank]

On 3/30/22 14:26, Claudio Imbrenda wrote:
> In upcoming patches it will be possible to start tearing down a
> protected VM, and finish the teardown concurrently in a different
> thread.
> 
> Protected VMs that are pending for tear down ("leftover") need to be
> cleaned properly when the userspace process (e.g. qemu) terminates.
> 
> This patch makes sure that all "leftover" protected VMs are always
> properly torn down.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
>   arch/s390/include/asm/kvm_host.h |  2 +
>   arch/s390/kvm/kvm-s390.c         |  1 +
>   arch/s390/kvm/pv.c               | 69 ++++++++++++++++++++++++++++++++
>   3 files changed, 72 insertions(+)
> 
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 1bccb8561ba9..50e3516cbc03 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -922,6 +922,8 @@ struct kvm_s390_pv {
>   	u64 guest_len;
>   	unsigned long stor_base;
>   	void *stor_var;
> +	void *async_deinit;
> +	struct list_head need_cleanup;
>   	struct mmu_notifier mmu_notifier;
>   };
>   
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 446f89db93a1..3637f556ff33 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2788,6 +2788,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>   	kvm_s390_vsie_init(kvm);
>   	if (use_gisa)
>   		kvm_s390_gisa_init(kvm);
> +	INIT_LIST_HEAD(&kvm->arch.pv.need_cleanup);

kvm->arch.pv.sync_deinit = NULL;

>   	KVM_EVENT(3, "vm 0x%pK created by pid %u", kvm, current->pid);
>   
>   	return 0;
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index be3b467f8feb..56412617dd01 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -17,6 +17,19 @@
>   #include <linux/mmu_notifier.h>
>   #include "kvm-s390.h"
>   
> +/**
> + * @struct deferred_priv
> + * Represents a "leftover" protected VM that does not correspond to any
> + * active KVM VM.

Maybe something like:
...that is still registered with the Ultravisor but isn't registered 
with KVM anymore.

> + */
> +struct deferred_priv {
> +	struct list_head list;
> +	unsigned long old_table;
> +	u64 handle;
> +	void *stor_var;
> +	unsigned long stor_base;
> +};
> +
>   static void kvm_s390_clear_pv_state(struct kvm *kvm)
>   {
>   	kvm->arch.pv.handle = 0;
> @@ -163,6 +176,60 @@ static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
>   	return -ENOMEM;
>   }
>   
> +/**
> + * kvm_s390_pv_cleanup_deferred - Clean up one leftover protected VM.
> + * @kvm the KVM that was associated with this leftover protected VM
> + * @deferred details about the leftover protected VM that needs a clean up
> + * Return: 0 in case of success, otherwise 1
> + */
> +static int kvm_s390_pv_cleanup_deferred(struct kvm *kvm, struct deferred_priv *deferred)
> +{
> +	u16 rc, rrc;
> +	int cc;
> +
> +	cc = uv_cmd_nodata(deferred->handle, UVC_CMD_DESTROY_SEC_CONF, &rc, &rrc);
> +	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", rc, rrc);
> +	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", rc, rrc);
> +	if (cc)
> +		return cc;
> +	/*
> +	 * Intentionally leak unusable memory. If the UVC fails, the memory
> +	 * used for the VM and its metadata is permanently unusable.
> +	 * This can only happen in case of a serious KVM or hardware bug; it
> +	 * is not expected to happen in normal operation.
> +	 */
> +	free_pages(deferred->stor_base, get_order(uv_info.guest_base_stor_len));
> +	free_pages(deferred->old_table, CRST_ALLOC_ORDER);
> +	vfree(deferred->stor_var);
> +	return 0;
> +}
> +
> +/**
> + * kvm_s390_pv_cleanup_leftovers - Clean up all leftover protected VMs.
> + * @kvm the KVM whose leftover protected VMs are to be cleaned up
> + * Return: 0 in case of success, otherwise 1
> + */
> +static int kvm_s390_pv_cleanup_leftovers(struct kvm *kvm)
> +{
> +	struct deferred_priv *deferred;
> +	int cc = 0;
> +
> +	if (kvm->arch.pv.async_deinit)
> +		list_add(kvm->arch.pv.async_deinit, &kvm->arch.pv.need_cleanup);
> +
> +	while (!list_empty(&kvm->arch.pv.need_cleanup)) {
> +		deferred = list_first_entry(&kvm->arch.pv.need_cleanup, typeof(*deferred), list);
> +		if (kvm_s390_pv_cleanup_deferred(kvm, deferred))
> +			cc = 1;
> +		else
> +			atomic_dec(&kvm->mm->context.protected_count);
> +		list_del(&deferred->list);
> +		kfree(deferred);
> +	}
> +	kvm->arch.pv.async_deinit = NULL;
> +	return cc;
> +}
> +
>   /* this should not fail, but if it does, we must not free the donated memory */
>   int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
>   {
> @@ -190,6 +257,8 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
>   	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
>   	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
>   
> +	cc |= kvm_s390_pv_cleanup_leftovers(kvm);
> +
>   	return cc ? -EIO : 0;
>   }
>   

Re: [PATCH v9 01/18] KVM: s390: pv: leak the topmost page table when destroy fails

[Claudio Imbrenda]

On Thu, 31 Mar 2022 15:13:41 +0200
Janosch Frank <frankja@linux.ibm.com> wrote:

> On 3/30/22 14:25, Claudio Imbrenda wrote:
> > Each secure guest must have a unique ASCE (address space control
> > element); we must avoid that new guests use the same page for their
> > ASCE, to avoid errors.
> > 
> > Since the ASCE mostly consists of the address of the topmost page table
> > (plus some flags), we must not return that memory to the pool unless
> > the ASCE is no longer in use.
> > 
> > Only a successful Destroy Secure Configuration UVC will make the ASCE
> > reusable again.
> > 
> > If the Destroy Configuration UVC fails, the ASCE cannot be reused for a
> > secure guest (either for the ASCE or for other memory areas). To avoid
> > a collision, it must not be used again. This is a permanent error and
> > the page becomes in practice unusable, so we set it aside and leak it.
> > On failure we already leak other memory that belongs to the ultravisor
> > (i.e. the variable and base storage for a guest) and not leaking the
> > topmost page table was an oversight.
> > 
> > This error (and thus the leakage) should not happen unless the hardware
> > is broken or KVM has some unknown serious bug.
> > 
> > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> > Fixes: 29b40f105ec8d55 ("KVM: s390: protvirt: Add initial vm and cpu lifecycle handling")
> > ---
> >   arch/s390/include/asm/gmap.h |  2 +
> >   arch/s390/kvm/pv.c           |  9 +++--
> >   arch/s390/mm/gmap.c          | 71 ++++++++++++++++++++++++++++++++++++
> >   3 files changed, 79 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
> > index 40264f60b0da..746e18bf8984 100644
> > --- a/arch/s390/include/asm/gmap.h
> > +++ b/arch/s390/include/asm/gmap.h
> > @@ -148,4 +148,6 @@ void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long dirty_bitmap[4],
> >   			     unsigned long gaddr, unsigned long vmaddr);
> >   int gmap_mark_unmergeable(void);
> >   void s390_reset_acc(struct mm_struct *mm);
> > +void s390_remove_old_asce(struct gmap *gmap);
> > +int s390_replace_asce(struct gmap *gmap);
> >   #endif /* _ASM_S390_GMAP_H */
> > diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> > index 7f7c0d6af2ce..3c59ef763dde 100644
> > --- a/arch/s390/kvm/pv.c
> > +++ b/arch/s390/kvm/pv.c
> > @@ -166,10 +166,13 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
> >   	atomic_set(&kvm->mm->context.is_protected, 0);
> >   	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
> >   	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
> > -	/* Inteded memory leak on "impossible" error */
> > -	if (!cc)
> > +	/* Intended memory leak on "impossible" error */
> > +	if (!cc) {
> >   		kvm_s390_pv_dealloc_vm(kvm);
> > -	return cc ? -EIO : 0;
> > +		return 0;
> > +	}
> > +	s390_replace_asce(kvm->arch.gmap);
> > +	return -EIO;
> >   }
> >   
> >   int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
> > diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> > index dfee0ebb2fac..3b42bf7adb77 100644
> > --- a/arch/s390/mm/gmap.c
> > +++ b/arch/s390/mm/gmap.c
> > @@ -2714,3 +2714,74 @@ void s390_reset_acc(struct mm_struct *mm)
> >   	mmput(mm);
> >   }
> >   EXPORT_SYMBOL_GPL(s390_reset_acc);
> > +
> > +/**
> > + * s390_remove_old_asce - Remove the topmost level of page tables from the
> > + * list of page tables of the gmap.
> > + * @gmap the gmap whose table is to be removed
> > + *
> > + * This means that it will not be freed when the VM is torn down, and needs
> > + * to be handled separately by the caller, unless an intentional leak is
> > + * intended. Notice that this function will only remove the page from the
> > + * list, the page will still be used as a top level page table (and ASCE).
> > + */
> > +void s390_remove_old_asce(struct gmap *gmap)
> > +{
> > +	struct page *old;
> > +
> > +	old = virt_to_page(gmap->table);
> > +	spin_lock(&gmap->guest_table_lock);
> > +	list_del(&old->lru);
> > +	/*
> > +	 * in case the ASCE needs to be "removed" multiple times, for example
> > +	 * if the VM is rebooted into secure mode several times
> > +	 * concurrently.
> > +	 */  
> 
> How can that happen, what are we protecting against here?

for example if replace_asce fails, and we call it again later. in that
case we have removed the old asce from the list ( = it won't be freed
when the VM terminates), but the ASCE is still in use and still pointed
to. a subsequent call to replace_asce will follow the pointer and try
to remove the same page from the list _again_.

Therefore it's necessary that the page of the ASCE has valid pointers,
so list_del can work (and do nothing) without dereferencing stale or
invalid pointers.

Maybe I should improve the comment

> 
> > +	INIT_LIST_HEAD(&old->lru);
> > +	spin_unlock(&gmap->guest_table_lock);
> > +}
> > +EXPORT_SYMBOL_GPL(s390_remove_old_asce);
> > +
> > +/**
> > + * s390_replace_asce - Try to replace the current ASCE of a gmap with
> > + * another equivalent one.
> > + * @gmap the gmap
> > + *
> > + * If the allocation of the new top level page table fails, the ASCE is not
> > + * replaced.
> > + * In any case, the old ASCE is always removed from the list. Therefore the
> > + * caller has to make sure to save a pointer to it beforehands, unless an
> > + * intentional leak is intended.
> > + */
> > +int s390_replace_asce(struct gmap *gmap)
> > +{
> > +	unsigned long asce;
> > +	struct page *page;
> > +	void *table;
> > +
> > +	s390_remove_old_asce(gmap);
> > +
> > +	page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
> > +	if (!page)
> > +		return -ENOMEM;
> > +	table = page_to_virt(page);
> > +	memcpy(table, gmap->table, 1UL << (CRST_ALLOC_ORDER + PAGE_SHIFT));
> > +
> > +	/*
> > +	 * The caller has to deal with the old ASCE, but here we make sure
> > +	 * the new one is properly added to the list of page tables, so that
> > +	 * it will be freed when the VM is torn down.
> > +	 */
> > +	spin_lock(&gmap->guest_table_lock);
> > +	list_add(&page->lru, &gmap->crst_list);
> > +	spin_unlock(&gmap->guest_table_lock);
> > +
> > +	/* Set new table origin while preserving existing ASCE control bits */
> > +	asce = (gmap->asce & ~_ASCE_ORIGIN) | __pa(table);
> > +	WRITE_ONCE(gmap->asce, asce);
> > +	WRITE_ONCE(gmap->mm->context.gmap_asce, asce);
> > +	WRITE_ONCE(gmap->table, table);
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(s390_replace_asce);  
> 

Re: [PATCH v9 04/18] KVM: s390: pv: refactor s390_reset_acc

[Claudio Imbrenda]

On Thu, 31 Mar 2022 15:25:31 +0200
Janosch Frank <frankja@linux.ibm.com> wrote:

> On 3/30/22 14:25, Claudio Imbrenda wrote:
> > Refactor s390_reset_acc so that it can be reused in upcoming patches.
> > 
> > We don't want to hold all the locks used in a walk_page_range for too
> > long, and the destroy page UVC does take some time to complete.
> > Therefore we quickly gather the pages to destroy, and then destroy them
> > without holding all the locks.
> > 
> > The new refactored function optionally allows to return early without
> > completing if a fatal signal is pending (and return and appropriate
> > error code). Two wrappers are provided to call the new function.
> > 
> > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> > (dropping Janosch's Ack because of major changes to the patch)  
> 
> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
> 
> [...]
> > +#define DESTROY_LOOP_THRESHOLD 32  
> 
> A question out of curiosity:
> Is there any particular reason for the number?
> Have you tested other numbers and experienced a speedup/slowdown?

to be honest no, it just seemed a good tradeoff between size and
callback overhead

> 
> > +
> > +struct reset_walk_state {
> > +	unsigned long next;
> > +	unsigned long count;
> > +	unsigned long pfns[DESTROY_LOOP_THRESHOLD];
> > +};
> > +
> > +static int s390_gather_pages(pte_t *ptep, unsigned long addr,
> > +			     unsigned long next, struct mm_walk *walk)
> >   {
> > +	struct reset_walk_state *p = walk->private;
> >   	pte_t pte = READ_ONCE(*ptep);
> >   
> > -	/* There is a reference through the mapping */
> > -	if (pte_present(pte))
> > -		WARN_ON_ONCE(uv_destroy_owned_page(pte_val(pte) & PAGE_MASK));
> > -
> > -	return 0;
> > +	if (pte_present(pte)) {
> > +		/* we have a reference from the mapping, take an extra one */
> > +		get_page(phys_to_page(pte_val(pte)));
> > +		p->pfns[p->count] = phys_to_pfn(pte_val(pte));
> > +		p->next = next;
> > +		p->count++;
> > +	}
> > +	return p->count >= DESTROY_LOOP_THRESHOLD;
> >   }
> >   
> > -static const struct mm_walk_ops reset_acc_walk_ops = {
> > -	.pte_entry		= __s390_reset_acc,
> > +static const struct mm_walk_ops gather_pages_ops = {
> > +	.pte_entry = s390_gather_pages,
> >   };
> >   
> > -#include <linux/sched/mm.h>
> > -void s390_reset_acc(struct mm_struct *mm)
> > +/*
> > + * Call the Destroy secure page UVC on each page in the given array of PFNs.
> > + * Each page needs to have an extra reference, which will be released here.
> > + */
> > +void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns)
> >   {
> > -	if (!mm_is_protected(mm))
> > -		return;
> > -	/*
> > -	 * we might be called during
> > -	 * reset:                             we walk the pages and clear
> > -	 * close of all kvm file descriptors: we walk the pages and clear
> > -	 * exit of process on fd closure:     vma already gone, do nothing
> > -	 */
> > -	if (!mmget_not_zero(mm))
> > -		return;
> > -	mmap_read_lock(mm);
> > -	walk_page_range(mm, 0, TASK_SIZE, &reset_acc_walk_ops, NULL);
> > -	mmap_read_unlock(mm);
> > -	mmput(mm);
> > +	unsigned long i;
> > +
> > +	for (i = 0; i < count; i++) {
> > +		/* we always have an extra reference */
> > +		uv_destroy_owned_page(pfn_to_phys(pfns[i]));
> > +		/* get rid of the extra reference */
> > +		put_page(pfn_to_page(pfns[i]));
> > +		cond_resched();
> > +	}
> > +}
> > +EXPORT_SYMBOL_GPL(s390_uv_destroy_pfns);
> > +
> > +/**
> > + * __s390_uv_destroy_range - Walk the given range of the given address
> > + * space, and call the destroy secure page UVC on each page.
> > + * Optionally exit early if a fatal signal is pending.
> > + * @mm the mm to operate on
> > + * @start the start of the range
> > + * @end the end of the range
> > + * @interruptible if not 0, stop when a fatal signal is received
> > + * Return: 0 on success, -EINTR if the function stopped before completing
> > + */
> > +int __s390_uv_destroy_range(struct mm_struct *mm, unsigned long start,
> > +			    unsigned long end, bool interruptible)
> > +{
> > +	struct reset_walk_state state = { .next = start };
> > +	int r = 1;
> > +
> > +	while (r > 0) {
> > +		state.count = 0;
> > +		mmap_read_lock(mm);
> > +		r = walk_page_range(mm, state.next, end, &gather_pages_ops, &state);
> > +		mmap_read_unlock(mm);
> > +		cond_resched();
> > +		s390_uv_destroy_pfns(state.count, state.pfns);
> > +		if (interruptible && fatal_signal_pending(current))
> > +			return -EINTR;
> > +	}
> > +	return 0;
> >   }
> > -EXPORT_SYMBOL_GPL(s390_reset_acc);
> > +EXPORT_SYMBOL_GPL(__s390_uv_destroy_range);
> >   
> >   /**
> >    * s390_remove_old_asce - Remove the topmost level of page tables from the  
> 

Re: [PATCH v9 11/18] s390/mm: KVM: pv: when tearing down, try to destroy protected pages

[Claudio Imbrenda]

On Thu, 31 Mar 2022 15:34:42 +0200
Janosch Frank <frankja@linux.ibm.com> wrote:

> On 3/30/22 14:25, Claudio Imbrenda wrote:
> > When ptep_get_and_clear_full is called for a mm teardown, we will now
> > attempt to destroy the secure pages. This will be faster than export.
> > 
> > In case it was not a teardown, or if for some reason the destroy page
> > UVC failed, we try with an export page, like before.
> > 
> > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> > Acked-by: Janosch Frank <frankja@linux.ibm.com>
> > ---
> >   arch/s390/include/asm/pgtable.h | 18 +++++++++++++++---
> >   1 file changed, 15 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
> > index 23ca0d8e058a..72544a1b4a68 100644
> > --- a/arch/s390/include/asm/pgtable.h
> > +++ b/arch/s390/include/asm/pgtable.h
> > @@ -1118,9 +1118,21 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
> >   	} else {
> >   		res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
> >   	}
> > -	/* At this point the reference through the mapping is still present */
> > -	if (mm_is_protected(mm) && pte_present(res))
> > -		uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
> > +	/* Nothing to do */
> > +	if (!mm_is_protected(mm) || !pte_present(res))
> > +		return res;
> > +	/*
> > +	 * At this point the reference through the mapping is still present.  
> 
> That's the case because we zap ptes within a mm that's still existing, 
> right? The mm will be deleted after we have unmapped the memory.

not exactly, the mm can exist without pages.

the reference is there because when we enter the function,
there is still a pointer to the page (the PTE itself), the page is still
reachable, and therefore its reference count cannot be less than 1.

when we leave the function, there is no more mapping for the page
(that's the point of the function after all), and only then the counter
can be decremented.

if you look at zap_pte_range in mm/memory.c, you see that we call
ptep_get_and_clear_full first, and then a few lines below we call
__tlb_remove_page which in the end calls put_page on that page.

> 
> 
> > +	 * The notifier should have destroyed all protected vCPUs at this
> > +	 * point, so the destroy should be successful.
> > +	 */
> > +	if (full && !uv_destroy_owned_page(pte_val(res) & PAGE_MASK))
> > +		return res;
> > +	/*
> > +	 * But if something went wrong and the pages could not be destroyed,
> > +	 * the slower export is used as fallback instead.
> > +	 */
> > +	uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
> >   	return res;
> >   }
> >     
> 

Re: [PATCH v9 13/18] KVM: s390: pv: cleanup leftover protected VMs if needed

[Claudio Imbrenda]

On Thu, 31 Mar 2022 16:02:55 +0200
Janosch Frank <frankja@linux.ibm.com> wrote:

> On 3/30/22 14:26, Claudio Imbrenda wrote:
> > In upcoming patches it will be possible to start tearing down a
> > protected VM, and finish the teardown concurrently in a different
> > thread.
> > 
> > Protected VMs that are pending for tear down ("leftover") need to be
> > cleaned properly when the userspace process (e.g. qemu) terminates.
> > 
> > This patch makes sure that all "leftover" protected VMs are always
> > properly torn down.
> > 
> > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> > ---
> >   arch/s390/include/asm/kvm_host.h |  2 +
> >   arch/s390/kvm/kvm-s390.c         |  1 +
> >   arch/s390/kvm/pv.c               | 69 ++++++++++++++++++++++++++++++++
> >   3 files changed, 72 insertions(+)
> > 
> > diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> > index 1bccb8561ba9..50e3516cbc03 100644
> > --- a/arch/s390/include/asm/kvm_host.h
> > +++ b/arch/s390/include/asm/kvm_host.h
> > @@ -922,6 +922,8 @@ struct kvm_s390_pv {
> >   	u64 guest_len;
> >   	unsigned long stor_base;
> >   	void *stor_var;
> > +	void *async_deinit;
> > +	struct list_head need_cleanup;
> >   	struct mmu_notifier mmu_notifier;
> >   };
> >   
> > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> > index 446f89db93a1..3637f556ff33 100644
> > --- a/arch/s390/kvm/kvm-s390.c
> > +++ b/arch/s390/kvm/kvm-s390.c
> > @@ -2788,6 +2788,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> >   	kvm_s390_vsie_init(kvm);
> >   	if (use_gisa)
> >   		kvm_s390_gisa_init(kvm);
> > +	INIT_LIST_HEAD(&kvm->arch.pv.need_cleanup);  
> 
> kvm->arch.pv.sync_deinit = NULL;

isn't the struct allocated with __GFP_ZERO ?

> 
> >   	KVM_EVENT(3, "vm 0x%pK created by pid %u", kvm, current->pid);
> >   
> >   	return 0;
> > diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> > index be3b467f8feb..56412617dd01 100644
> > --- a/arch/s390/kvm/pv.c
> > +++ b/arch/s390/kvm/pv.c
> > @@ -17,6 +17,19 @@
> >   #include <linux/mmu_notifier.h>
> >   #include "kvm-s390.h"
> >   
> > +/**
> > + * @struct deferred_priv
> > + * Represents a "leftover" protected VM that does not correspond to any
> > + * active KVM VM.  
> 
> Maybe something like:
> ...that is still registered with the Ultravisor but isn't registered 
> with KVM anymore.

will fix

> 
> > + */
> > +struct deferred_priv {
> > +	struct list_head list;
> > +	unsigned long old_table;
> > +	u64 handle;
> > +	void *stor_var;
> > +	unsigned long stor_base;
> > +};
> > +
> >   static void kvm_s390_clear_pv_state(struct kvm *kvm)
> >   {
> >   	kvm->arch.pv.handle = 0;
> > @@ -163,6 +176,60 @@ static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
> >   	return -ENOMEM;
> >   }
> >   
> > +/**
> > + * kvm_s390_pv_cleanup_deferred - Clean up one leftover protected VM.
> > + * @kvm the KVM that was associated with this leftover protected VM
> > + * @deferred details about the leftover protected VM that needs a clean up
> > + * Return: 0 in case of success, otherwise 1
> > + */
> > +static int kvm_s390_pv_cleanup_deferred(struct kvm *kvm, struct deferred_priv *deferred)
> > +{
> > +	u16 rc, rrc;
> > +	int cc;
> > +
> > +	cc = uv_cmd_nodata(deferred->handle, UVC_CMD_DESTROY_SEC_CONF, &rc, &rrc);
> > +	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", rc, rrc);
> > +	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", rc, rrc);
> > +	if (cc)
> > +		return cc;
> > +	/*
> > +	 * Intentionally leak unusable memory. If the UVC fails, the memory
> > +	 * used for the VM and its metadata is permanently unusable.
> > +	 * This can only happen in case of a serious KVM or hardware bug; it
> > +	 * is not expected to happen in normal operation.
> > +	 */
> > +	free_pages(deferred->stor_base, get_order(uv_info.guest_base_stor_len));
> > +	free_pages(deferred->old_table, CRST_ALLOC_ORDER);
> > +	vfree(deferred->stor_var);
> > +	return 0;
> > +}
> > +
> > +/**
> > + * kvm_s390_pv_cleanup_leftovers - Clean up all leftover protected VMs.
> > + * @kvm the KVM whose leftover protected VMs are to be cleaned up
> > + * Return: 0 in case of success, otherwise 1
> > + */
> > +static int kvm_s390_pv_cleanup_leftovers(struct kvm *kvm)
> > +{
> > +	struct deferred_priv *deferred;
> > +	int cc = 0;
> > +
> > +	if (kvm->arch.pv.async_deinit)
> > +		list_add(kvm->arch.pv.async_deinit, &kvm->arch.pv.need_cleanup);
> > +
> > +	while (!list_empty(&kvm->arch.pv.need_cleanup)) {
> > +		deferred = list_first_entry(&kvm->arch.pv.need_cleanup, typeof(*deferred), list);
> > +		if (kvm_s390_pv_cleanup_deferred(kvm, deferred))
> > +			cc = 1;
> > +		else
> > +			atomic_dec(&kvm->mm->context.protected_count);
> > +		list_del(&deferred->list);
> > +		kfree(deferred);
> > +	}
> > +	kvm->arch.pv.async_deinit = NULL;
> > +	return cc;
> > +}
> > +
> >   /* this should not fail, but if it does, we must not free the donated memory */
> >   int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
> >   {
> > @@ -190,6 +257,8 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
> >   	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
> >   	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
> >   
> > +	cc |= kvm_s390_pv_cleanup_leftovers(kvm);
> > +
> >   	return cc ? -EIO : 0;
> >   }
> >     
>