[PATCH v4 0/5] KVM: Unify mmu_memory_cache functionality across architectures

[PATCH v4 0/5] KVM: Unify mmu_memory_cache functionality across architectures

[Christoffer Dall]

We currently have duplicated functionality for the mmu_memory_cache used
to pre-allocate memory for the page table manipulation code which cannot
allocate memory while holding spinlocks.  This functionality is
duplicated across x86, arm/arm64, and mips.

This was motivated by a debate of modifying the arm code to be more in
line with the x86 code and some discussions around changing the page
flags used for allocation.  This series should make it easier to take a
uniform approach across architectures.

While there's not a huge amount of code sharing, we come out with a net
gain, and the real win is in the consistency of how we allocate memory
for page tables used by secondary MMUs driven by KVM in Linux.

Only tested on arm/arm64, and only compile-tested on x86 and mips.  I'm
especially curious on getting feedback on the change of GFP flags for
x86 (patch 1) and on the use of __GFP_ACCOUNT for mips.

Changes since v3:
 - Moved to common GFP_PGTABLE_USER definition for page allocations in
   the MMU cache for all three architectures.  This follows recent work
   which already did this for arm/arm64.
 - Rebased on v5.4-rc4.

Changes since v2:
 - Simplified kalloc flag definitions as per Paolo's review comment.

Changes since v1:
 - Split out rename from initial x86 patch to have separate patches to
   move the logic to common code and to rename.
 - Introduce KVM_ARCH_WANT_MMU_MEMCACHE to avoid compile breakage on
   architectures that don't use this functionality.
 - Rename KVM_NR_MEM_OBJS to KVM_MMU_NR_MEMCACHE_OBJS

Christoffer Dall (5):
  KVM: x86: Move memcache allocation to GFP_PGTABLE_USER
  KVM: x86: Move mmu_memory_cache functions to common code
  KVM: x86: Rename mmu_memory_cache to kvm_mmu_memcache
  KVM: arm/arm64: Move to common kvm_mmu_memcache infrastructure
  KVM: mips: Move to common kvm_mmu_memcache infrastructure

 arch/arm/include/asm/kvm_host.h      | 13 +---
 arch/arm/include/asm/kvm_mmu.h       |  2 +-
 arch/arm/include/asm/kvm_types.h     |  9 +++
 arch/arm64/include/asm/kvm_host.h    | 13 +---
 arch/arm64/include/asm/kvm_mmu.h     |  2 +-
 arch/arm64/include/asm/kvm_types.h   |  9 +++
 arch/mips/include/asm/kvm_host.h     | 15 +----
 arch/mips/include/asm/kvm_types.h    |  9 +++
 arch/mips/kvm/mips.c                 |  2 +-
 arch/mips/kvm/mmu.c                  | 54 +++-------------
 arch/powerpc/include/asm/kvm_types.h |  5 ++
 arch/s390/include/asm/kvm_types.h    |  5 ++
 arch/x86/include/asm/kvm_host.h      | 17 +----
 arch/x86/include/asm/kvm_types.h     |  9 +++
 arch/x86/kvm/mmu.c                   | 97 ++++++----------------------
 arch/x86/kvm/paging_tmpl.h           |  4 +-
 include/linux/kvm_host.h             | 11 ++++
 include/linux/kvm_types.h            | 13 ++++
 virt/kvm/arm/arm.c                   |  2 +-
 virt/kvm/arm/mmu.c                   | 68 +++++--------------
 virt/kvm/kvm_main.c                  | 61 +++++++++++++++++
 21 files changed, 190 insertions(+), 230 deletions(-)
 create mode 100644 arch/arm/include/asm/kvm_types.h
 create mode 100644 arch/arm64/include/asm/kvm_types.h
 create mode 100644 arch/mips/include/asm/kvm_types.h
 create mode 100644 arch/powerpc/include/asm/kvm_types.h
 create mode 100644 arch/s390/include/asm/kvm_types.h
 create mode 100644 arch/x86/include/asm/kvm_types.h

-- 
2.18.0

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[PATCH v4 1/5] KVM: x86: Move memcache allocation to GFP_PGTABLE_USER

[Christoffer Dall]

Recent commit 50f11a8a4620eee6b6831e69ab5d42456546d7d8 moved page table
allocations for both KVM and normal user page table allocations to
GFP_PGTABLE_USER in order to get __GFP_ACCOUNT for the page tables.

However, while KVM on other architectures such as arm64 were included in
this change, curiously KVM on x86 was not.

Currently, KVM on x86 uses kmem_cache_zalloc(GFP_KERNEL_ACCOUNT) for
kmem_cache-based allocations, which expands in the following way:
  kmem_cache_zalloc(..., GFP_KERNEL_ACCOUNT) =>
  kmem_cache_alloc(..., GFP_KERNEL_ACCOUNT | __GFP_ZERO) =>
  kmem_cache_alloc(..., GFP_KERNEL | __GFP_ACCOUNT | __GFP_ZERO)

It so happens that GFP_PGTABLE_USER expands as:
  GFP_PGTABLE_USER =>
  (GFP_PGTABLE_KERNEL | __GFP_ACCOUNT) =>
  ((GFP_KERNEL | __GFP_ZERO) | __GFP_ACCOUNT) =>
  (GFP_KERNEL | __GFP_ACCOUNT | __GFP_ZERO)

Which means that we can replace the current KVM on x86 call as:
-  obj = kmem_cache_zalloc(base_cache, GFP_KERNEL_ACCOUNT);
+  obj = kmem_cache_alloc(base_cache, GFP_PGTABLE_USER);

For the single page cache topup allocation, KVM on x86 currently uses
__get_free_page(GFP_KERNEL_ACCOUNT).  It seems to me that is equivalent
to the above, except that the allocated page is not guaranteed to be
zero (unless I missed the place where __get_free_page(!__GFP_ZERO) is
still guaranteed to be zeroed.  It seems natural (and in fact desired)
to have both topup functions implement the same expectations towards the
caller, and we therefore move to GFP_PGTABLE_USER here as well.

This will make it easier to unify the memchace implementation between
architectures.

Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
---
 arch/x86/kvm/mmu.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 24c23c66b226..540190cee3cb 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -40,6 +40,7 @@
 
 #include <asm/page.h>
 #include <asm/pat.h>
+#include <asm/pgalloc.h>
 #include <asm/cmpxchg.h>
 #include <asm/e820/api.h>
 #include <asm/io.h>
@@ -1025,7 +1026,7 @@ static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
 	if (cache->nobjs >= min)
 		return 0;
 	while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
-		obj = kmem_cache_zalloc(base_cache, GFP_KERNEL_ACCOUNT);
+		obj = kmem_cache_alloc(base_cache, GFP_PGTABLE_USER);
 		if (!obj)
 			return cache->nobjs >= min ? 0 : -ENOMEM;
 		cache->objects[cache->nobjs++] = obj;
@@ -1053,7 +1054,7 @@ static int mmu_topup_memory_cache_page(struct kvm_mmu_memory_cache *cache,
 	if (cache->nobjs >= min)
 		return 0;
 	while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
-		page = (void *)__get_free_page(GFP_KERNEL_ACCOUNT);
+		page = (void *)__get_free_page(GFP_PGTABLE_USER);
 		if (!page)
 			return cache->nobjs >= min ? 0 : -ENOMEM;
 		cache->objects[cache->nobjs++] = page;
-- 
2.18.0

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[PATCH v4 2/5] KVM: x86: Move mmu_memory_cache functions to common code

[Christoffer Dall]

We are currently duplicating the mmu memory cache functionality quite
heavily between the architectures that support KVM.  As a first step,
move the x86 implementation (which seems to have the most recently
maintained version of the mmu memory cache) to common code.

We introduce an arch-specific kvm_types.h which can be used to specify
how many objects are required in the memory cache, an aspect which
diverges across architectures.  Since kvm_host.h defines structures with
fields of the memcache object, we define the memcache structure in
kvm_types.h, and we include the architecture-specific kvm_types.h to
know the size of object in kvm_host.h.

We only define the functions and data types if
KVM_ARCH_WANT_MMU_MEMORY_CACHE is defined, because not all architectures
require the mmu memory cache.

Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
---
 arch/arm/include/asm/kvm_types.h     |  5 +++
 arch/arm64/include/asm/kvm_types.h   |  6 +++
 arch/mips/include/asm/kvm_types.h    |  5 +++
 arch/powerpc/include/asm/kvm_types.h |  5 +++
 arch/s390/include/asm/kvm_types.h    |  5 +++
 arch/x86/include/asm/kvm_host.h      | 11 -----
 arch/x86/include/asm/kvm_types.h     |  9 ++++
 arch/x86/kvm/mmu.c                   | 60 ---------------------------
 include/linux/kvm_host.h             | 11 +++++
 include/linux/kvm_types.h            | 13 ++++++
 virt/kvm/kvm_main.c                  | 61 ++++++++++++++++++++++++++++
 11 files changed, 120 insertions(+), 71 deletions(-)
 create mode 100644 arch/arm/include/asm/kvm_types.h
 create mode 100644 arch/arm64/include/asm/kvm_types.h
 create mode 100644 arch/mips/include/asm/kvm_types.h
 create mode 100644 arch/powerpc/include/asm/kvm_types.h
 create mode 100644 arch/s390/include/asm/kvm_types.h
 create mode 100644 arch/x86/include/asm/kvm_types.h

diff --git a/arch/arm/include/asm/kvm_types.h b/arch/arm/include/asm/kvm_types.h
new file mode 100644
index 000000000000..bc389f82e88d
--- /dev/null
+++ b/arch/arm/include/asm/kvm_types.h
@@ -0,0 +1,5 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARM_KVM_TYPES_H
+#define _ASM_ARM_KVM_TYPES_H
+
+#endif /* _ASM_ARM_KVM_TYPES_H */
diff --git a/arch/arm64/include/asm/kvm_types.h b/arch/arm64/include/asm/kvm_types.h
new file mode 100644
index 000000000000..d0987007d581
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_types.h
@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARM64_KVM_TYPES_H
+#define _ASM_ARM64_KVM_TYPES_H
+
+#endif /* _ASM_ARM64_KVM_TYPES_H */
+
diff --git a/arch/mips/include/asm/kvm_types.h b/arch/mips/include/asm/kvm_types.h
new file mode 100644
index 000000000000..5efeb32a5926
--- /dev/null
+++ b/arch/mips/include/asm/kvm_types.h
@@ -0,0 +1,5 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_MIPS_KVM_TYPES_H
+#define _ASM_MIPS_KVM_TYPES_H
+
+#endif /* _ASM_MIPS_KVM_TYPES_H */
diff --git a/arch/powerpc/include/asm/kvm_types.h b/arch/powerpc/include/asm/kvm_types.h
new file mode 100644
index 000000000000..f627eceaa314
--- /dev/null
+++ b/arch/powerpc/include/asm/kvm_types.h
@@ -0,0 +1,5 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_POWERPC_KVM_TYPES_H
+#define _ASM_POWERPC_KVM_TYPES_H
+
+#endif /* _ASM_POWERPC_KVM_TYPES_H */
diff --git a/arch/s390/include/asm/kvm_types.h b/arch/s390/include/asm/kvm_types.h
new file mode 100644
index 000000000000..b66a81f8a354
--- /dev/null
+++ b/arch/s390/include/asm/kvm_types.h
@@ -0,0 +1,5 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_S390_KVM_TYPES_H
+#define _ASM_S390_KVM_TYPES_H
+
+#endif /* _ASM_S390_KVM_TYPES_H */
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 50eb430b0ad8..e5080b618f3c 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -179,8 +179,6 @@ enum {
 
 #include <asm/kvm_emulate.h>
 
-#define KVM_NR_MEM_OBJS 40
-
 #define KVM_NR_DB_REGS	4
 
 #define DR6_BD		(1 << 13)
@@ -231,15 +229,6 @@ enum {
 
 struct kvm_kernel_irq_routing_entry;
 
-/*
- * We don't want allocation failures within the mmu code, so we preallocate
- * enough memory for a single page fault in a cache.
- */
-struct kvm_mmu_memory_cache {
-	int nobjs;
-	void *objects[KVM_NR_MEM_OBJS];
-};
-
 /*
  * the pages used as guest page table on soft mmu are tracked by
  * kvm_memory_slot.arch.gfn_track which is 16 bits, so the role bits used
diff --git a/arch/x86/include/asm/kvm_types.h b/arch/x86/include/asm/kvm_types.h
new file mode 100644
index 000000000000..40428651dc7a
--- /dev/null
+++ b/arch/x86/include/asm/kvm_types.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_KVM_TYPES_H
+#define _ASM_X86_KVM_TYPES_H
+
+#define KVM_ARCH_WANT_MMU_MEMORY_CACHE
+
+#define KVM_NR_MEM_OBJS 40
+
+#endif /* _ASM_X86_KVM_TYPES_H */
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 540190cee3cb..abcdb47b0ac7 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -40,7 +40,6 @@
 
 #include <asm/page.h>
 #include <asm/pat.h>
-#include <asm/pgalloc.h>
 #include <asm/cmpxchg.h>
 #include <asm/e820/api.h>
 #include <asm/io.h>
@@ -1018,56 +1017,6 @@ static void walk_shadow_page_lockless_end(struct kvm_vcpu *vcpu)
 	local_irq_enable();
 }
 
-static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
-				  struct kmem_cache *base_cache, int min)
-{
-	void *obj;
-
-	if (cache->nobjs >= min)
-		return 0;
-	while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
-		obj = kmem_cache_alloc(base_cache, GFP_PGTABLE_USER);
-		if (!obj)
-			return cache->nobjs >= min ? 0 : -ENOMEM;
-		cache->objects[cache->nobjs++] = obj;
-	}
-	return 0;
-}
-
-static int mmu_memory_cache_free_objects(struct kvm_mmu_memory_cache *cache)
-{
-	return cache->nobjs;
-}
-
-static void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc,
-				  struct kmem_cache *cache)
-{
-	while (mc->nobjs)
-		kmem_cache_free(cache, mc->objects[--mc->nobjs]);
-}
-
-static int mmu_topup_memory_cache_page(struct kvm_mmu_memory_cache *cache,
-				       int min)
-{
-	void *page;
-
-	if (cache->nobjs >= min)
-		return 0;
-	while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
-		page = (void *)__get_free_page(GFP_PGTABLE_USER);
-		if (!page)
-			return cache->nobjs >= min ? 0 : -ENOMEM;
-		cache->objects[cache->nobjs++] = page;
-	}
-	return 0;
-}
-
-static void mmu_free_memory_cache_page(struct kvm_mmu_memory_cache *mc)
-{
-	while (mc->nobjs)
-		free_page((unsigned long)mc->objects[--mc->nobjs]);
-}
-
 static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
 {
 	int r;
@@ -1094,15 +1043,6 @@ static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
 				mmu_page_header_cache);
 }
 
-static void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc)
-{
-	void *p;
-
-	BUG_ON(!mc->nobjs);
-	p = mc->objects[--mc->nobjs];
-	return p;
-}
-
 static struct pte_list_desc *mmu_alloc_pte_list_desc(struct kvm_vcpu *vcpu)
 {
 	return mmu_memory_cache_alloc(&vcpu->arch.mmu_pte_list_desc_cache);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 719fc3e15ea4..612922d440cc 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -788,6 +788,17 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu, bool usermode_vcpu_not_eligible);
 void kvm_flush_remote_tlbs(struct kvm *kvm);
 void kvm_reload_remote_mmus(struct kvm *kvm);
 
+#ifdef KVM_ARCH_WANT_MMU_MEMORY_CACHE
+int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
+			   struct kmem_cache *base_cache, int min);
+int mmu_memory_cache_free_objects(struct kvm_mmu_memory_cache *cache);
+void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc,
+			   struct kmem_cache *cache);
+int mmu_topup_memory_cache_page(struct kvm_mmu_memory_cache *cache, int min);
+void mmu_free_memory_cache_page(struct kvm_mmu_memory_cache *mc);
+void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc);
+#endif
+
 bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
 				 unsigned long *vcpu_bitmap, cpumask_var_t tmp);
 bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req);
diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
index bde5374ae021..ca7d3b3c8487 100644
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -18,6 +18,7 @@ struct kvm_memslots;
 
 enum kvm_mr_change;
 
+#include <asm/kvm_types.h>
 #include <asm/types.h>
 
 /*
@@ -49,4 +50,16 @@ struct gfn_to_hva_cache {
 	struct kvm_memory_slot *memslot;
 };
 
+#ifdef KVM_ARCH_WANT_MMU_MEMORY_CACHE
+/*
+ * We don't want allocation failures within the mmu code, so we preallocate
+ * enough memory for a single page fault in a cache.
+ */
+struct kvm_mmu_memory_cache {
+	int nobjs;
+	void *objects[KVM_NR_MEM_OBJS];
+};
+#endif
+
+
 #endif /* __KVM_TYPES_H__ */
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index fd68fbe0a75d..a4e8297152e9 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -51,6 +51,7 @@
 #include <linux/io.h>
 #include <linux/lockdep.h>
 
+#include <asm/pgalloc.h>
 #include <asm/processor.h>
 #include <asm/ioctl.h>
 #include <linux/uaccess.h>
@@ -288,6 +289,66 @@ void kvm_reload_remote_mmus(struct kvm *kvm)
 	kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_RELOAD);
 }
 
+#ifdef KVM_ARCH_WANT_MMU_MEMORY_CACHE
+int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
+			   struct kmem_cache *base_cache, int min)
+{
+	void *obj;
+
+	if (cache->nobjs >= min)
+		return 0;
+	while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
+		obj = kmem_cache_alloc(base_cache, GFP_PGTABLE_USER);
+		if (!obj)
+			return cache->nobjs >= min ? 0 : -ENOMEM;
+		cache->objects[cache->nobjs++] = obj;
+	}
+	return 0;
+}
+
+int mmu_memory_cache_free_objects(struct kvm_mmu_memory_cache *cache)
+{
+	return cache->nobjs;
+}
+
+void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc,
+			   struct kmem_cache *cache)
+{
+	while (mc->nobjs)
+		kmem_cache_free(cache, mc->objects[--mc->nobjs]);
+}
+
+int mmu_topup_memory_cache_page(struct kvm_mmu_memory_cache *cache, int min)
+{
+	void *page;
+
+	if (cache->nobjs >= min)
+		return 0;
+	while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
+		page = (void *)__get_free_page(GFP_PGTABLE_USER);
+		if (!page)
+			return cache->nobjs >= min ? 0 : -ENOMEM;
+		cache->objects[cache->nobjs++] = page;
+	}
+	return 0;
+}
+
+void mmu_free_memory_cache_page(struct kvm_mmu_memory_cache *mc)
+{
+	while (mc->nobjs)
+		free_page((unsigned long)mc->objects[--mc->nobjs]);
+}
+
+void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc)
+{
+	void *p;
+
+	BUG_ON(!mc->nobjs);
+	p = mc->objects[--mc->nobjs];
+	return p;
+}
+#endif
+
 int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
 {
 	struct page *page;
-- 
2.18.0

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[PATCH v4 3/5] KVM: x86: Rename mmu_memory_cache to kvm_mmu_memcache

[Christoffer Dall]

As we have moved the mmu memory cache definitions and functions to
common code, they are exported as symols to the rest of the kernel.

Let's rename the functions and data types to have a kvm_ prefix to make
it clear where these functions belong and take this chance to rename
memory_cache to memcache to avoid overly long lines.

This is a bit tedious on the callsites but ends up looking more
palatable.

Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
---
 arch/x86/include/asm/kvm_host.h  |  6 ++---
 arch/x86/include/asm/kvm_types.h |  4 ++--
 arch/x86/kvm/mmu.c               | 38 ++++++++++++++++----------------
 arch/x86/kvm/paging_tmpl.h       |  4 ++--
 include/linux/kvm_host.h         | 14 ++++++------
 include/linux/kvm_types.h        |  6 ++---
 virt/kvm/kvm_main.c              | 14 ++++++------
 7 files changed, 43 insertions(+), 43 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e5080b618f3c..47e183ca0fb2 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -586,9 +586,9 @@ struct kvm_vcpu_arch {
 	 */
 	struct kvm_mmu *walk_mmu;
 
-	struct kvm_mmu_memory_cache mmu_pte_list_desc_cache;
-	struct kvm_mmu_memory_cache mmu_page_cache;
-	struct kvm_mmu_memory_cache mmu_page_header_cache;
+	struct kvm_mmu_memcache mmu_pte_list_desc_cache;
+	struct kvm_mmu_memcache mmu_page_cache;
+	struct kvm_mmu_memcache mmu_page_header_cache;
 
 	/*
 	 * QEMU userspace and the guest each have their own FPU state.
diff --git a/arch/x86/include/asm/kvm_types.h b/arch/x86/include/asm/kvm_types.h
index 40428651dc7a..d391490ab8d1 100644
--- a/arch/x86/include/asm/kvm_types.h
+++ b/arch/x86/include/asm/kvm_types.h
@@ -2,8 +2,8 @@
 #ifndef _ASM_X86_KVM_TYPES_H
 #define _ASM_X86_KVM_TYPES_H
 
-#define KVM_ARCH_WANT_MMU_MEMORY_CACHE
+#define KVM_ARCH_WANT_MMU_MEMCACHE
 
-#define KVM_NR_MEM_OBJS 40
+#define KVM_MMU_NR_MEMCACHE_OBJS 40
 
 #endif /* _ASM_X86_KVM_TYPES_H */
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index abcdb47b0ac7..431ac346a1e8 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1017,35 +1017,35 @@ static void walk_shadow_page_lockless_end(struct kvm_vcpu *vcpu)
 	local_irq_enable();
 }
 
-static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
+static int kvm_mmu_topup_memcaches(struct kvm_vcpu *vcpu)
 {
 	int r;
 
-	r = mmu_topup_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache,
+	r = kvm_mmu_topup_memcache(&vcpu->arch.mmu_pte_list_desc_cache,
 				   pte_list_desc_cache, 8 + PTE_PREFETCH_NUM);
 	if (r)
 		goto out;
-	r = mmu_topup_memory_cache_page(&vcpu->arch.mmu_page_cache, 8);
+	r = kvm_mmu_topup_memcache_page(&vcpu->arch.mmu_page_cache, 8);
 	if (r)
 		goto out;
-	r = mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache,
+	r = kvm_mmu_topup_memcache(&vcpu->arch.mmu_page_header_cache,
 				   mmu_page_header_cache, 4);
 out:
 	return r;
 }
 
-static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
+static void kvm_mmu_free_memcaches(struct kvm_vcpu *vcpu)
 {
-	mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache,
+	kvm_mmu_free_memcache(&vcpu->arch.mmu_pte_list_desc_cache,
 				pte_list_desc_cache);
-	mmu_free_memory_cache_page(&vcpu->arch.mmu_page_cache);
-	mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache,
+	kvm_mmu_free_memcache_page(&vcpu->arch.mmu_page_cache);
+	kvm_mmu_free_memcache(&vcpu->arch.mmu_page_header_cache,
 				mmu_page_header_cache);
 }
 
 static struct pte_list_desc *mmu_alloc_pte_list_desc(struct kvm_vcpu *vcpu)
 {
-	return mmu_memory_cache_alloc(&vcpu->arch.mmu_pte_list_desc_cache);
+	return kvm_mmu_memcache_alloc(&vcpu->arch.mmu_pte_list_desc_cache);
 }
 
 static void mmu_free_pte_list_desc(struct pte_list_desc *pte_list_desc)
@@ -1371,10 +1371,10 @@ static struct kvm_rmap_head *gfn_to_rmap(struct kvm *kvm, gfn_t gfn,
 
 static bool rmap_can_add(struct kvm_vcpu *vcpu)
 {
-	struct kvm_mmu_memory_cache *cache;
+	struct kvm_mmu_memcache *cache;
 
 	cache = &vcpu->arch.mmu_pte_list_desc_cache;
-	return mmu_memory_cache_free_objects(cache);
+	return kvm_mmu_memcache_free_objects(cache);
 }
 
 static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
@@ -2062,10 +2062,10 @@ static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu, int direct
 {
 	struct kvm_mmu_page *sp;
 
-	sp = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
-	sp->spt = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache);
+	sp = kvm_mmu_memcache_alloc(&vcpu->arch.mmu_page_header_cache);
+	sp->spt = kvm_mmu_memcache_alloc(&vcpu->arch.mmu_page_cache);
 	if (!direct)
-		sp->gfns = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache);
+		sp->gfns = kvm_mmu_memcache_alloc(&vcpu->arch.mmu_page_cache);
 	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
 
 	/*
@@ -4005,7 +4005,7 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
 	if (page_fault_handle_page_track(vcpu, error_code, gfn))
 		return RET_PF_EMULATE;
 
-	r = mmu_topup_memory_caches(vcpu);
+	r = kvm_mmu_topup_memcaches(vcpu);
 	if (r)
 		return r;
 
@@ -4121,7 +4121,7 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
 	if (page_fault_handle_page_track(vcpu, error_code, gfn))
 		return RET_PF_EMULATE;
 
-	r = mmu_topup_memory_caches(vcpu);
+	r = kvm_mmu_topup_memcaches(vcpu);
 	if (r)
 		return r;
 
@@ -5102,7 +5102,7 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
 {
 	int r;
 
-	r = mmu_topup_memory_caches(vcpu);
+	r = kvm_mmu_topup_memcaches(vcpu);
 	if (r)
 		goto out;
 	r = mmu_alloc_roots(vcpu);
@@ -5280,7 +5280,7 @@ static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
 	 * or not since pte prefetch is skiped if it does not have
 	 * enough objects in the cache.
 	 */
-	mmu_topup_memory_caches(vcpu);
+	kvm_mmu_topup_memcaches(vcpu);
 
 	spin_lock(&vcpu->kvm->mmu_lock);
 
@@ -6169,7 +6169,7 @@ void kvm_mmu_destroy(struct kvm_vcpu *vcpu)
 	kvm_mmu_unload(vcpu);
 	free_mmu_pages(&vcpu->arch.root_mmu);
 	free_mmu_pages(&vcpu->arch.guest_mmu);
-	mmu_free_memory_caches(vcpu);
+	kvm_mmu_free_memcaches(vcpu);
 }
 
 void kvm_mmu_module_exit(void)
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 7d5cdb3af594..106bb08c11ee 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -765,7 +765,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
 
 	pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);
 
-	r = mmu_topup_memory_caches(vcpu);
+	r = kvm_mmu_topup_memcaches(vcpu);
 	if (r)
 		return r;
 
@@ -885,7 +885,7 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa)
 	 * No need to check return value here, rmap_can_add() can
 	 * help us to skip pte prefetch later.
 	 */
-	mmu_topup_memory_caches(vcpu);
+	kvm_mmu_topup_memcaches(vcpu);
 
 	if (!VALID_PAGE(root_hpa)) {
 		WARN_ON(1);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 612922d440cc..c832b925d4ee 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -788,15 +788,15 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu, bool usermode_vcpu_not_eligible);
 void kvm_flush_remote_tlbs(struct kvm *kvm);
 void kvm_reload_remote_mmus(struct kvm *kvm);
 
-#ifdef KVM_ARCH_WANT_MMU_MEMORY_CACHE
-int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
+#ifdef KVM_ARCH_WANT_MMU_MEMCACHE
+int kvm_mmu_topup_memcache(struct kvm_mmu_memcache *cache,
 			   struct kmem_cache *base_cache, int min);
-int mmu_memory_cache_free_objects(struct kvm_mmu_memory_cache *cache);
-void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc,
+int kvm_mmu_memcache_free_objects(struct kvm_mmu_memcache *cache);
+void kvm_mmu_free_memcache(struct kvm_mmu_memcache *mc,
 			   struct kmem_cache *cache);
-int mmu_topup_memory_cache_page(struct kvm_mmu_memory_cache *cache, int min);
-void mmu_free_memory_cache_page(struct kvm_mmu_memory_cache *mc);
-void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc);
+int kvm_mmu_topup_memcache_page(struct kvm_mmu_memcache *cache, int min);
+void kvm_mmu_free_memcache_page(struct kvm_mmu_memcache *mc);
+void *kvm_mmu_memcache_alloc(struct kvm_mmu_memcache *mc);
 #endif
 
 bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
index ca7d3b3c8487..bfe59aa55736 100644
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -50,14 +50,14 @@ struct gfn_to_hva_cache {
 	struct kvm_memory_slot *memslot;
 };
 
-#ifdef KVM_ARCH_WANT_MMU_MEMORY_CACHE
+#ifdef KVM_ARCH_WANT_MMU_MEMCACHE
 /*
  * We don't want allocation failures within the mmu code, so we preallocate
  * enough memory for a single page fault in a cache.
  */
-struct kvm_mmu_memory_cache {
+struct kvm_mmu_memcache {
 	int nobjs;
-	void *objects[KVM_NR_MEM_OBJS];
+	void *objects[KVM_MMU_NR_MEMCACHE_OBJS];
 };
 #endif
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a4e8297152e9..278a881ca3e3 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -289,8 +289,8 @@ void kvm_reload_remote_mmus(struct kvm *kvm)
 	kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_RELOAD);
 }
 
-#ifdef KVM_ARCH_WANT_MMU_MEMORY_CACHE
-int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
+#ifdef KVM_ARCH_WANT_MMU_MEMCACHE
+int kvm_mmu_topup_memcache(struct kvm_mmu_memcache *cache,
 			   struct kmem_cache *base_cache, int min)
 {
 	void *obj;
@@ -306,19 +306,19 @@ int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
 	return 0;
 }
 
-int mmu_memory_cache_free_objects(struct kvm_mmu_memory_cache *cache)
+int kvm_mmu_memcache_free_objects(struct kvm_mmu_memcache *cache)
 {
 	return cache->nobjs;
 }
 
-void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc,
+void kvm_mmu_free_memcache(struct kvm_mmu_memcache *mc,
 			   struct kmem_cache *cache)
 {
 	while (mc->nobjs)
 		kmem_cache_free(cache, mc->objects[--mc->nobjs]);
 }
 
-int mmu_topup_memory_cache_page(struct kvm_mmu_memory_cache *cache, int min)
+int kvm_mmu_topup_memcache_page(struct kvm_mmu_memcache *cache, int min)
 {
 	void *page;
 
@@ -333,13 +333,13 @@ int mmu_topup_memory_cache_page(struct kvm_mmu_memory_cache *cache, int min)
 	return 0;
 }
 
-void mmu_free_memory_cache_page(struct kvm_mmu_memory_cache *mc)
+void kvm_mmu_free_memcache_page(struct kvm_mmu_memcache *mc)
 {
 	while (mc->nobjs)
 		free_page((unsigned long)mc->objects[--mc->nobjs]);
 }
 
-void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc)
+void *kvm_mmu_memcache_alloc(struct kvm_mmu_memcache *mc)
 {
 	void *p;
 
-- 
2.18.0

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

[PATCH v4 4/5] KVM: arm/arm64: Move to common kvm_mmu_memcache infrastructure

[Christoffer Dall]

Now when we have a common mmu mmemcache implementation, we can reuse
this for arm and arm64.

The common implementation has a slightly different behavior when
allocating objects under high memory pressure; whereas the current
arm/arm64 implementation will give up and return -ENOMEM if the full
size of the cache cannot be allocated during topup, the common
implementation is happy with any allocation between min and max.  There
should be no architecture-specific requirement for doing it one way or
the other and it's in fact better to enforce a cross-architecture KVM
policy on this behavior.

Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
---
 arch/arm/include/asm/kvm_host.h    | 13 +-----
 arch/arm/include/asm/kvm_mmu.h     |  2 +-
 arch/arm/include/asm/kvm_types.h   |  4 ++
 arch/arm64/include/asm/kvm_host.h  | 13 +-----
 arch/arm64/include/asm/kvm_mmu.h   |  2 +-
 arch/arm64/include/asm/kvm_types.h |  5 ++-
 virt/kvm/arm/arm.c                 |  2 +-
 virt/kvm/arm/mmu.c                 | 68 ++++++++----------------------
 8 files changed, 30 insertions(+), 79 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 8a37c8e89777..04e7c5868132 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -78,17 +78,6 @@ struct kvm_arch {
 	u32 psci_version;
 };
 
-#define KVM_NR_MEM_OBJS     40
-
-/*
- * We don't want allocation failures within the mmu code, so we preallocate
- * enough memory for a single page fault in a cache.
- */
-struct kvm_mmu_memory_cache {
-	int nobjs;
-	void *objects[KVM_NR_MEM_OBJS];
-};
-
 struct kvm_vcpu_fault_info {
 	u32 hsr;		/* Hyp Syndrome Register */
 	u32 hxfar;		/* Hyp Data/Inst. Fault Address Register */
@@ -196,7 +185,7 @@ struct kvm_vcpu_arch {
 	struct kvm_decode mmio_decode;
 
 	/* Cache some mmu pages needed inside spinlock regions */
-	struct kvm_mmu_memory_cache mmu_page_cache;
+	struct kvm_mmu_memcache mmu_page_cache;
 
 	struct vcpu_reset_state reset_state;
 
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 0d84d50bf9ba..b1ff76aac0cd 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -59,7 +59,7 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
 
 int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run);
 
-void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu);
+void kvm_mmu_free_memcaches(struct kvm_vcpu *vcpu);
 
 phys_addr_t kvm_mmu_get_httbr(void);
 phys_addr_t kvm_get_idmap_vector(void);
diff --git a/arch/arm/include/asm/kvm_types.h b/arch/arm/include/asm/kvm_types.h
index bc389f82e88d..de5be31a5a77 100644
--- a/arch/arm/include/asm/kvm_types.h
+++ b/arch/arm/include/asm/kvm_types.h
@@ -2,4 +2,8 @@
 #ifndef _ASM_ARM_KVM_TYPES_H
 #define _ASM_ARM_KVM_TYPES_H
 
+#define KVM_ARCH_WANT_MMU_MEMCACHE
+
+#define KVM_MMU_NR_MEMCACHE_OBJS 40
+
 #endif /* _ASM_ARM_KVM_TYPES_H */
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index f656169db8c3..00b8d1f65e44 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -85,17 +85,6 @@ struct kvm_arch {
 	u32 psci_version;
 };
 
-#define KVM_NR_MEM_OBJS     40
-
-/*
- * We don't want allocation failures within the mmu code, so we preallocate
- * enough memory for a single page fault in a cache.
- */
-struct kvm_mmu_memory_cache {
-	int nobjs;
-	void *objects[KVM_NR_MEM_OBJS];
-};
-
 struct kvm_vcpu_fault_info {
 	u32 esr_el2;		/* Hyp Syndrom Register */
 	u64 far_el2;		/* Hyp Fault Address Register */
@@ -320,7 +309,7 @@ struct kvm_vcpu_arch {
 	struct kvm_decode mmio_decode;
 
 	/* Cache some mmu pages needed inside spinlock regions */
-	struct kvm_mmu_memory_cache mmu_page_cache;
+	struct kvm_mmu_memcache mmu_page_cache;
 
 	/* Target CPU and feature flags */
 	int target;
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index befe37d4bc0e..e23e91f368ae 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -160,7 +160,7 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
 
 int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run);
 
-void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu);
+void kvm_mmu_free_memcaches(struct kvm_vcpu *vcpu);
 
 phys_addr_t kvm_mmu_get_httbr(void);
 phys_addr_t kvm_get_idmap_vector(void);
diff --git a/arch/arm64/include/asm/kvm_types.h b/arch/arm64/include/asm/kvm_types.h
index d0987007d581..89b15f62e466 100644
--- a/arch/arm64/include/asm/kvm_types.h
+++ b/arch/arm64/include/asm/kvm_types.h
@@ -2,5 +2,8 @@
 #ifndef _ASM_ARM64_KVM_TYPES_H
 #define _ASM_ARM64_KVM_TYPES_H
 
-#endif /* _ASM_ARM64_KVM_TYPES_H */
+#define KVM_ARCH_WANT_MMU_MEMCACHE
+
+#define KVM_MMU_NR_MEMCACHE_OBJS 40
 
+#endif /* _ASM_ARM64_KVM_TYPES_H */
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 86c6aa1cb58e..96e2df4f8fc9 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -300,7 +300,7 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
 	if (vcpu->arch.has_run_once && unlikely(!irqchip_in_kernel(vcpu->kvm)))
 		static_branch_dec(&userspace_irqchip_in_use);
 
-	kvm_mmu_free_memory_caches(vcpu);
+	kvm_mmu_free_memcaches(vcpu);
 	kvm_timer_vcpu_terminate(vcpu);
 	kvm_pmu_vcpu_destroy(vcpu);
 	kvm_vcpu_uninit(vcpu);
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 38b4c910b6c3..0daa79230226 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -120,38 +120,6 @@ static void stage2_dissolve_pud(struct kvm *kvm, phys_addr_t addr, pud_t *pudp)
 	put_page(virt_to_page(pudp));
 }
 
-static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
-				  int min, int max)
-{
-	void *page;
-
-	BUG_ON(max > KVM_NR_MEM_OBJS);
-	if (cache->nobjs >= min)
-		return 0;
-	while (cache->nobjs < max) {
-		page = (void *)__get_free_page(GFP_PGTABLE_USER);
-		if (!page)
-			return -ENOMEM;
-		cache->objects[cache->nobjs++] = page;
-	}
-	return 0;
-}
-
-static void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc)
-{
-	while (mc->nobjs)
-		free_page((unsigned long)mc->objects[--mc->nobjs]);
-}
-
-static void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc)
-{
-	void *p;
-
-	BUG_ON(!mc || !mc->nobjs);
-	p = mc->objects[--mc->nobjs];
-	return p;
-}
-
 static void clear_stage2_pgd_entry(struct kvm *kvm, pgd_t *pgd, phys_addr_t addr)
 {
 	pud_t *pud_table __maybe_unused = stage2_pud_offset(kvm, pgd, 0UL);
@@ -1008,7 +976,7 @@ void kvm_free_stage2_pgd(struct kvm *kvm)
 		free_pages_exact(pgd, stage2_pgd_size(kvm));
 }
 
-static pud_t *stage2_get_pud(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
+static pud_t *stage2_get_pud(struct kvm *kvm, struct kvm_mmu_memcache *cache,
 			     phys_addr_t addr)
 {
 	pgd_t *pgd;
@@ -1018,7 +986,7 @@ static pud_t *stage2_get_pud(struct kvm *kvm, struct kvm_mmu_memory_cache *cache
 	if (stage2_pgd_none(kvm, *pgd)) {
 		if (!cache)
 			return NULL;
-		pud = mmu_memory_cache_alloc(cache);
+		pud = kvm_mmu_memcache_alloc(cache);
 		stage2_pgd_populate(kvm, pgd, pud);
 		get_page(virt_to_page(pgd));
 	}
@@ -1026,7 +994,7 @@ static pud_t *stage2_get_pud(struct kvm *kvm, struct kvm_mmu_memory_cache *cache
 	return stage2_pud_offset(kvm, pgd, addr);
 }
 
-static pmd_t *stage2_get_pmd(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
+static pmd_t *stage2_get_pmd(struct kvm *kvm, struct kvm_mmu_memcache *cache,
 			     phys_addr_t addr)
 {
 	pud_t *pud;
@@ -1039,7 +1007,7 @@ static pmd_t *stage2_get_pmd(struct kvm *kvm, struct kvm_mmu_memory_cache *cache
 	if (stage2_pud_none(kvm, *pud)) {
 		if (!cache)
 			return NULL;
-		pmd = mmu_memory_cache_alloc(cache);
+		pmd = kvm_mmu_memcache_alloc(cache);
 		stage2_pud_populate(kvm, pud, pmd);
 		get_page(virt_to_page(pud));
 	}
@@ -1047,7 +1015,7 @@ static pmd_t *stage2_get_pmd(struct kvm *kvm, struct kvm_mmu_memory_cache *cache
 	return stage2_pmd_offset(kvm, pud, addr);
 }
 
-static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache
+static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memcache
 			       *cache, phys_addr_t addr, const pmd_t *new_pmd)
 {
 	pmd_t *pmd, old_pmd;
@@ -1111,7 +1079,7 @@ static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache
 	return 0;
 }
 
-static int stage2_set_pud_huge(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
+static int stage2_set_pud_huge(struct kvm *kvm, struct kvm_mmu_memcache *cache,
 			       phys_addr_t addr, const pud_t *new_pudp)
 {
 	pud_t *pudp, old_pud;
@@ -1213,7 +1181,7 @@ static bool stage2_is_exec(struct kvm *kvm, phys_addr_t addr)
 		return kvm_s2pte_exec(ptep);
 }
 
-static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
+static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memcache *cache,
 			  phys_addr_t addr, const pte_t *new_pte,
 			  unsigned long flags)
 {
@@ -1245,7 +1213,7 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
 	if (stage2_pud_none(kvm, *pud)) {
 		if (!cache)
 			return 0; /* ignore calls from kvm_set_spte_hva */
-		pmd = mmu_memory_cache_alloc(cache);
+		pmd = kvm_mmu_memcache_alloc(cache);
 		stage2_pud_populate(kvm, pud, pmd);
 		get_page(virt_to_page(pud));
 	}
@@ -1270,7 +1238,7 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
 	if (pmd_none(*pmd)) {
 		if (!cache)
 			return 0; /* ignore calls from kvm_set_spte_hva */
-		pte = mmu_memory_cache_alloc(cache);
+		pte = kvm_mmu_memcache_alloc(cache);
 		kvm_pmd_populate(pmd, pte);
 		get_page(virt_to_page(pmd));
 	}
@@ -1337,7 +1305,7 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
 	phys_addr_t addr, end;
 	int ret = 0;
 	unsigned long pfn;
-	struct kvm_mmu_memory_cache cache = { 0, };
+	struct kvm_mmu_memcache cache = { 0, };
 
 	end = (guest_ipa + size + PAGE_SIZE - 1) & PAGE_MASK;
 	pfn = __phys_to_pfn(pa);
@@ -1348,9 +1316,8 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
 		if (writable)
 			pte = kvm_s2pte_mkwrite(pte);
 
-		ret = mmu_topup_memory_cache(&cache,
-					     kvm_mmu_cache_min_pages(kvm),
-					     KVM_NR_MEM_OBJS);
+		ret = kvm_mmu_topup_memcache_page(&cache,
+						  kvm_mmu_cache_min_pages(kvm));
 		if (ret)
 			goto out;
 		spin_lock(&kvm->mmu_lock);
@@ -1364,7 +1331,7 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
 	}
 
 out:
-	mmu_free_memory_cache(&cache);
+	kvm_mmu_free_memcache_page(&cache);
 	return ret;
 }
 
@@ -1671,7 +1638,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	unsigned long mmu_seq;
 	gfn_t gfn = fault_ipa >> PAGE_SHIFT;
 	struct kvm *kvm = vcpu->kvm;
-	struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
+	struct kvm_mmu_memcache *memcache = &vcpu->arch.mmu_page_cache;
 	struct vm_area_struct *vma;
 	kvm_pfn_t pfn;
 	pgprot_t mem_type = PAGE_S2;
@@ -1716,8 +1683,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	up_read(&current->mm->mmap_sem);
 
 	/* We need minimum second+third level pages */
-	ret = mmu_topup_memory_cache(memcache, kvm_mmu_cache_min_pages(kvm),
-				     KVM_NR_MEM_OBJS);
+	ret = kvm_mmu_topup_memcache_page(memcache, kvm_mmu_cache_min_pages(kvm));
 	if (ret)
 		return ret;
 
@@ -2137,9 +2103,9 @@ int kvm_test_age_hva(struct kvm *kvm, unsigned long hva)
 	return handle_hva_to_gpa(kvm, hva, hva, kvm_test_age_hva_handler, NULL);
 }
 
-void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu)
+void kvm_mmu_free_memcaches(struct kvm_vcpu *vcpu)
 {
-	mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
+	kvm_mmu_free_memcache_page(&vcpu->arch.mmu_page_cache);
 }
 
 phys_addr_t kvm_mmu_get_httbr(void)
-- 
2.18.0

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[PATCH v4 5/5] KVM: mips: Move to common kvm_mmu_memcache infrastructure

[Christoffer Dall]

Now that we have a common infrastructure for doing MMU cache
allocations, use this for mips as well.

This will change the GFP flags used for mips from plain GFP_KERNEL to
GFP_PGTABLE_USER.  This means that mips KVM page table allocations now
gain __GFP_ACCOUNT and __GFP_ZERO.  There should be no harm in the
former, and while the latter might result in slight overhead for zeroing
the page, it seems this is what a hypervisor should do on page table
allocations.

Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
---
 arch/mips/include/asm/kvm_host.h  | 15 ++-------
 arch/mips/include/asm/kvm_types.h |  4 +++
 arch/mips/kvm/mips.c              |  2 +-
 arch/mips/kvm/mmu.c               | 54 ++++++-------------------------
 4 files changed, 17 insertions(+), 58 deletions(-)

diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index 41204a49cf95..418c941f1382 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -293,17 +293,6 @@ struct kvm_mips_tlb {
 	long tlb_lo[2];
 };
 
-#define KVM_NR_MEM_OBJS     4
-
-/*
- * We don't want allocation failures within the mmu code, so we preallocate
- * enough memory for a single page fault in a cache.
- */
-struct kvm_mmu_memory_cache {
-	int nobjs;
-	void *objects[KVM_NR_MEM_OBJS];
-};
-
 #define KVM_MIPS_AUX_FPU	0x1
 #define KVM_MIPS_AUX_MSA	0x2
 
@@ -378,7 +367,7 @@ struct kvm_vcpu_arch {
 	unsigned int last_user_gasid;
 
 	/* Cache some mmu pages needed inside spinlock regions */
-	struct kvm_mmu_memory_cache mmu_page_cache;
+	struct kvm_mmu_memcache mmu_page_cache;
 
 #ifdef CONFIG_KVM_MIPS_VZ
 	/* vcpu's vzguestid is different on each host cpu in an smp system */
@@ -915,7 +904,7 @@ void kvm_mips_flush_gva_pt(pgd_t *pgd, enum kvm_mips_flush flags);
 bool kvm_mips_flush_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn);
 int kvm_mips_mkclean_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn);
 pgd_t *kvm_pgd_alloc(void);
-void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu);
+void kvm_mmu_free_memcaches(struct kvm_vcpu *vcpu);
 void kvm_trap_emul_invalidate_gva(struct kvm_vcpu *vcpu, unsigned long addr,
 				  bool user);
 void kvm_trap_emul_gva_lockless_begin(struct kvm_vcpu *vcpu);
diff --git a/arch/mips/include/asm/kvm_types.h b/arch/mips/include/asm/kvm_types.h
index 5efeb32a5926..c7b906568a0e 100644
--- a/arch/mips/include/asm/kvm_types.h
+++ b/arch/mips/include/asm/kvm_types.h
@@ -2,4 +2,8 @@
 #ifndef _ASM_MIPS_KVM_TYPES_H
 #define _ASM_MIPS_KVM_TYPES_H
 
+#define KVM_ARCH_WANT_MMU_MEMCACHE
+
+#define KVM_MMU_NR_MEMCACHE_OBJS 4
+
 #endif /* _ASM_MIPS_KVM_TYPES_H */
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 1109924560d8..8bf12ed539b5 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -415,7 +415,7 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
 
 	kvm_mips_dump_stats(vcpu);
 
-	kvm_mmu_free_memory_caches(vcpu);
+	kvm_mmu_free_memcaches(vcpu);
 	kfree(vcpu->arch.guest_ebase);
 	kfree(vcpu->arch.kseg0_commpage);
 	kfree(vcpu);
diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c
index 97e538a8c1be..aed5284d642e 100644
--- a/arch/mips/kvm/mmu.c
+++ b/arch/mips/kvm/mmu.c
@@ -25,41 +25,9 @@
 #define KVM_MMU_CACHE_MIN_PAGES 2
 #endif
 
-static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
-				  int min, int max)
+void kvm_mmu_free_memcaches(struct kvm_vcpu *vcpu)
 {
-	void *page;
-
-	BUG_ON(max > KVM_NR_MEM_OBJS);
-	if (cache->nobjs >= min)
-		return 0;
-	while (cache->nobjs < max) {
-		page = (void *)__get_free_page(GFP_KERNEL);
-		if (!page)
-			return -ENOMEM;
-		cache->objects[cache->nobjs++] = page;
-	}
-	return 0;
-}
-
-static void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc)
-{
-	while (mc->nobjs)
-		free_page((unsigned long)mc->objects[--mc->nobjs]);
-}
-
-static void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc)
-{
-	void *p;
-
-	BUG_ON(!mc || !mc->nobjs);
-	p = mc->objects[--mc->nobjs];
-	return p;
-}
-
-void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu)
-{
-	mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
+	kvm_mmu_free_memcache_page(&vcpu->arch.mmu_page_cache);
 }
 
 /**
@@ -133,7 +101,7 @@ pgd_t *kvm_pgd_alloc(void)
  *		NULL if a page table doesn't exist for @addr and !@cache.
  *		NULL if a page table allocation failed.
  */
-static pte_t *kvm_mips_walk_pgd(pgd_t *pgd, struct kvm_mmu_memory_cache *cache,
+static pte_t *kvm_mips_walk_pgd(pgd_t *pgd, struct kvm_mmu_memcache *cache,
 				unsigned long addr)
 {
 	pud_t *pud;
@@ -151,7 +119,7 @@ static pte_t *kvm_mips_walk_pgd(pgd_t *pgd, struct kvm_mmu_memory_cache *cache,
 
 		if (!cache)
 			return NULL;
-		new_pmd = mmu_memory_cache_alloc(cache);
+		new_pmd = kvm_mmu_memcache_alloc(cache);
 		pmd_init((unsigned long)new_pmd,
 			 (unsigned long)invalid_pte_table);
 		pud_populate(NULL, pud, new_pmd);
@@ -162,7 +130,7 @@ static pte_t *kvm_mips_walk_pgd(pgd_t *pgd, struct kvm_mmu_memory_cache *cache,
 
 		if (!cache)
 			return NULL;
-		new_pte = mmu_memory_cache_alloc(cache);
+		new_pte = kvm_mmu_memcache_alloc(cache);
 		clear_page(new_pte);
 		pmd_populate_kernel(NULL, pmd, new_pte);
 	}
@@ -171,7 +139,7 @@ static pte_t *kvm_mips_walk_pgd(pgd_t *pgd, struct kvm_mmu_memory_cache *cache,
 
 /* Caller must hold kvm->mm_lock */
 static pte_t *kvm_mips_pte_for_gpa(struct kvm *kvm,
-				   struct kvm_mmu_memory_cache *cache,
+				   struct kvm_mmu_memcache *cache,
 				   unsigned long addr)
 {
 	return kvm_mips_walk_pgd(kvm->arch.gpa_mm.pgd, cache, addr);
@@ -688,7 +656,7 @@ static int kvm_mips_map_page(struct kvm_vcpu *vcpu, unsigned long gpa,
 			     pte_t *out_entry, pte_t *out_buddy)
 {
 	struct kvm *kvm = vcpu->kvm;
-	struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
+	struct kvm_mmu_memcache *memcache = &vcpu->arch.mmu_page_cache;
 	gfn_t gfn = gpa >> PAGE_SHIFT;
 	int srcu_idx, err;
 	kvm_pfn_t pfn;
@@ -705,8 +673,7 @@ static int kvm_mips_map_page(struct kvm_vcpu *vcpu, unsigned long gpa,
 		goto out;
 
 	/* We need a minimum of cached pages ready for page table creation */
-	err = mmu_topup_memory_cache(memcache, KVM_MMU_CACHE_MIN_PAGES,
-				     KVM_NR_MEM_OBJS);
+	err = kvm_mmu_topup_memcache_page(memcache, KVM_MMU_CACHE_MIN_PAGES);
 	if (err)
 		goto out;
 
@@ -785,13 +752,12 @@ static int kvm_mips_map_page(struct kvm_vcpu *vcpu, unsigned long gpa,
 static pte_t *kvm_trap_emul_pte_for_gva(struct kvm_vcpu *vcpu,
 					unsigned long addr)
 {
-	struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
+	struct kvm_mmu_memcache *memcache = &vcpu->arch.mmu_page_cache;
 	pgd_t *pgdp;
 	int ret;
 
 	/* We need a minimum of cached pages ready for page table creation */
-	ret = mmu_topup_memory_cache(memcache, KVM_MMU_CACHE_MIN_PAGES,
-				     KVM_NR_MEM_OBJS);
+	ret = kvm_mmu_topup_memcache_page(memcache, KVM_MMU_CACHE_MIN_PAGES);
 	if (ret)
 		return NULL;
 
-- 
2.18.0

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Re: [PATCH v4 1/5] KVM: x86: Move memcache allocation to GFP_PGTABLE_USER

[Sean Christopherson]

On Tue, Nov 05, 2019 at 12:03:53PM +0100, Christoffer Dall wrote:
> Recent commit 50f11a8a4620eee6b6831e69ab5d42456546d7d8 moved page table
> allocations for both KVM and normal user page table allocations to
> GFP_PGTABLE_USER in order to get __GFP_ACCOUNT for the page tables.
> 
> However, while KVM on other architectures such as arm64 were included in
> this change, curiously KVM on x86 was not.
> 
> Currently, KVM on x86 uses kmem_cache_zalloc(GFP_KERNEL_ACCOUNT) for
> kmem_cache-based allocations, which expands in the following way:
>   kmem_cache_zalloc(..., GFP_KERNEL_ACCOUNT) =>
>   kmem_cache_alloc(..., GFP_KERNEL_ACCOUNT | __GFP_ZERO) =>
>   kmem_cache_alloc(..., GFP_KERNEL | __GFP_ACCOUNT | __GFP_ZERO)
> 
> It so happens that GFP_PGTABLE_USER expands as:
>   GFP_PGTABLE_USER =>
>   (GFP_PGTABLE_KERNEL | __GFP_ACCOUNT) =>
>   ((GFP_KERNEL | __GFP_ZERO) | __GFP_ACCOUNT) =>
>   (GFP_KERNEL | __GFP_ACCOUNT | __GFP_ZERO)
> 
> Which means that we can replace the current KVM on x86 call as:
> -  obj = kmem_cache_zalloc(base_cache, GFP_KERNEL_ACCOUNT);
> +  obj = kmem_cache_alloc(base_cache, GFP_PGTABLE_USER);
> 
> For the single page cache topup allocation, KVM on x86 currently uses
> __get_free_page(GFP_KERNEL_ACCOUNT).  It seems to me that is equivalent
> to the above, except that the allocated page is not guaranteed to be
> zero (unless I missed the place where __get_free_page(!__GFP_ZERO) is
> still guaranteed to be zeroed.  It seems natural (and in fact desired)
> to have both topup functions implement the same expectations towards the
> caller, and we therefore move to GFP_PGTABLE_USER here as well.
> 
> This will make it easier to unify the memchace implementation between
> architectures.

Functionally, this looks correct (I haven't actually tested).  But, it
means that x86's shadow pages will be zeroed out twice, which could lead
to performance regressions.  The cache is also used for the gfns array,
and I'm pretty sure the gfns array is never zeroed out in the current code,
i.e. zeroing gfns would also introduce overhead.

The redudant zeroing of shadow pages could likely be addressed by removing
the call to clear_page() in kvm_mmu_get_page(), but I'd prefer not to go
that route because it doesn't address the gfns issue, means KVM pays the
cost of zeroing up front (as opposed to when a page is actually used), and
I have a future use case where the shadow page needs to be initialized to
a non-zero value.

What about having the common mmu_topup_memory_cache{_page}() take a GFP
param?  That would allow consolidating the bulk of the code while allowing
x86 to optimize its specific scenarios.

> Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
> ---
>  arch/x86/kvm/mmu.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 24c23c66b226..540190cee3cb 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -40,6 +40,7 @@
>  
>  #include <asm/page.h>
>  #include <asm/pat.h>
> +#include <asm/pgalloc.h>
>  #include <asm/cmpxchg.h>
>  #include <asm/e820/api.h>
>  #include <asm/io.h>
> @@ -1025,7 +1026,7 @@ static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
>  	if (cache->nobjs >= min)
>  		return 0;
>  	while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
> -		obj = kmem_cache_zalloc(base_cache, GFP_KERNEL_ACCOUNT);
> +		obj = kmem_cache_alloc(base_cache, GFP_PGTABLE_USER);
>  		if (!obj)
>  			return cache->nobjs >= min ? 0 : -ENOMEM;
>  		cache->objects[cache->nobjs++] = obj;
> @@ -1053,7 +1054,7 @@ static int mmu_topup_memory_cache_page(struct kvm_mmu_memory_cache *cache,
>  	if (cache->nobjs >= min)
>  		return 0;
>  	while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
> -		page = (void *)__get_free_page(GFP_KERNEL_ACCOUNT);
> +		page = (void *)__get_free_page(GFP_PGTABLE_USER);
>  		if (!page)
>  			return cache->nobjs >= min ? 0 : -ENOMEM;
>  		cache->objects[cache->nobjs++] = page;
> -- 
> 2.18.0
> 
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