[PATCH v2 1/7] KVM: MMU: optimize pte write path if don't have protected sp

[PATCH v2 1/7] KVM: MMU: optimize pte write path if don't have protected sp

[Xiao Guangrong]

Simply return from kvm_mmu_pte_write path if no shadow page is
write-protected, then we can avoid to walk all shadow pages and hold
mmu-lock

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/include/asm/kvm_host.h |    1 +
 arch/x86/kvm/mmu.c              |    9 +++++++++
 2 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d2ac8e2..152601a 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -441,6 +441,7 @@ struct kvm_arch {
 	unsigned int n_used_mmu_pages;
 	unsigned int n_requested_mmu_pages;
 	unsigned int n_max_mmu_pages;
+	unsigned int indirect_shadow_pages;
 	atomic_t invlpg_counter;
 	struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];
 	/*
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 2841805..ad520d4 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -498,6 +498,7 @@ static void account_shadowed(struct kvm *kvm, gfn_t gfn)
 		linfo = lpage_info_slot(gfn, slot, i);
 		linfo->write_count += 1;
 	}
+	kvm->arch.indirect_shadow_pages++;
 }
 
 static void unaccount_shadowed(struct kvm *kvm, gfn_t gfn)
@@ -513,6 +514,7 @@ static void unaccount_shadowed(struct kvm *kvm, gfn_t gfn)
 		linfo->write_count -= 1;
 		WARN_ON(linfo->write_count < 0);
 	}
+	kvm->arch.indirect_shadow_pages--;
 }
 
 static int has_wrprotected_page(struct kvm *kvm,
@@ -3233,6 +3235,13 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
 	int level, npte, invlpg_counter, r, flooded = 0;
 	bool remote_flush, local_flush, zap_page;
 
+	/*
+	 * If we don't have indirect shadow pages, it means no page is
+	 * write-protected, so we can exit simply.
+	 */
+	if (!ACCESS_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
+		return;
+
 	zap_page = remote_flush = local_flush = false;
 	offset = offset_in_page(gpa);
 
-- 
1.7.4.4

[PATCH v2 2/7] KVM: use __copy_to_user/__clear_user to write guest page

[Xiao Guangrong]

Simply use __copy_to_user/__clear_user to write guest page since we have
already verified the user address when the memslot is set

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/kvm/x86.c  |    4 ++--
 virt/kvm/kvm_main.c |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 77c9d86..a419bd1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1388,7 +1388,7 @@ static int set_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 			return 1;
 		kvm_x86_ops->patch_hypercall(vcpu, instructions);
 		((unsigned char *)instructions)[3] = 0xc3; /* ret */
-		if (copy_to_user((void __user *)addr, instructions, 4))
+		if (__copy_to_user((void __user *)addr, instructions, 4))
 			return 1;
 		kvm->arch.hv_hypercall = data;
 		break;
@@ -1415,7 +1415,7 @@ static int set_msr_hyperv(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 				  HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT);
 		if (kvm_is_error_hva(addr))
 			return 1;
-		if (clear_user((void __user *)addr, PAGE_SIZE))
+		if (__clear_user((void __user *)addr, PAGE_SIZE))
 			return 1;
 		vcpu->arch.hv_vapic = data;
 		break;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 22cdb96..3962899 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1342,7 +1342,7 @@ int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data,
 	addr = gfn_to_hva(kvm, gfn);
 	if (kvm_is_error_hva(addr))
 		return -EFAULT;
-	r = copy_to_user((void __user *)addr + offset, data, len);
+	r = __copy_to_user((void __user *)addr + offset, data, len);
 	if (r)
 		return -EFAULT;
 	mark_page_dirty(kvm, gfn);
@@ -1402,7 +1402,7 @@ int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
 	if (kvm_is_error_hva(ghc->hva))
 		return -EFAULT;
 
-	r = copy_to_user((void __user *)ghc->hva, data, len);
+	r = __copy_to_user((void __user *)ghc->hva, data, len);
 	if (r)
 		return -EFAULT;
 	mark_page_dirty_in_slot(kvm, ghc->memslot, ghc->gpa >> PAGE_SHIFT);
-- 
1.7.4.4

[PATCH v2 3/7] KVM: fix uninitialized warning

[Xiao Guangrong]

Fix:

 warning: ‘cs_sel’ may be used uninitialized in this function
 warning: ‘ss_sel’ may be used uninitialized in this function

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/kvm/emulate.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 291c872..ea32340 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2015,7 +2015,7 @@ emulate_sysexit(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
 	struct desc_struct cs, ss;
 	u64 msr_data;
 	int usermode;
-	u16 cs_sel, ss_sel;
+	u16 cs_sel = 0, ss_sel = 0;
 
 	/* inject #GP if in real mode or Virtual 8086 mode */
 	if (ctxt->mode == X86EMUL_MODE_REAL ||
-- 
1.7.4.4

[PATCH v2 4/7] KVM: MMU: abstract the operation of rmap

[Xiao Guangrong]

Abstract the operation of rmap to spte_list, then we can use it for the
reverse mapping of parent pte in the later patch

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/include/asm/kvm_host.h |    2 +-
 arch/x86/kvm/mmu.c              |  260 +++++++++++++++++++++------------------
 2 files changed, 140 insertions(+), 122 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 152601a..0d824e4 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -347,7 +347,7 @@ struct kvm_vcpu_arch {
 	struct kvm_pv_mmu_op_buffer mmu_op_buffer;
 
 	struct kvm_mmu_memory_cache mmu_pte_chain_cache;
-	struct kvm_mmu_memory_cache mmu_rmap_desc_cache;
+	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;
 
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ad520d4..5ba347b 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -148,7 +148,7 @@ module_param(oos_shadow, bool, 0644);
 #define PT64_PERM_MASK (PT_PRESENT_MASK | PT_WRITABLE_MASK | PT_USER_MASK \
 			| PT64_NX_MASK)
 
-#define RMAP_EXT 4
+#define PTE_LIST_EXT 4
 
 #define ACC_EXEC_MASK    1
 #define ACC_WRITE_MASK   PT_WRITABLE_MASK
@@ -164,9 +164,9 @@ module_param(oos_shadow, bool, 0644);
 
 #define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)
 
-struct kvm_rmap_desc {
-	u64 *sptes[RMAP_EXT];
-	struct kvm_rmap_desc *more;
+struct pte_list_desc {
+	u64 *sptes[PTE_LIST_EXT];
+	struct pte_list_desc *more;
 };
 
 struct kvm_shadow_walk_iterator {
@@ -185,7 +185,7 @@ struct kvm_shadow_walk_iterator {
 typedef void (*mmu_parent_walk_fn) (struct kvm_mmu_page *sp, u64 *spte);
 
 static struct kmem_cache *pte_chain_cache;
-static struct kmem_cache *rmap_desc_cache;
+static struct kmem_cache *pte_list_desc_cache;
 static struct kmem_cache *mmu_page_header_cache;
 static struct percpu_counter kvm_total_used_mmu_pages;
 
@@ -401,8 +401,8 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
 				   pte_chain_cache, 4);
 	if (r)
 		goto out;
-	r = mmu_topup_memory_cache(&vcpu->arch.mmu_rmap_desc_cache,
-				   rmap_desc_cache, 4 + PTE_PREFETCH_NUM);
+	r = mmu_topup_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache,
+				   pte_list_desc_cache, 4 + PTE_PREFETCH_NUM);
 	if (r)
 		goto out;
 	r = mmu_topup_memory_cache_page(&vcpu->arch.mmu_page_cache, 8);
@@ -416,8 +416,10 @@ out:
 
 static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
 {
-	mmu_free_memory_cache(&vcpu->arch.mmu_pte_chain_cache, pte_chain_cache);
-	mmu_free_memory_cache(&vcpu->arch.mmu_rmap_desc_cache, rmap_desc_cache);
+	mmu_free_memory_cache(&vcpu->arch.mmu_pte_chain_cache,
+				pte_chain_cache);
+	mmu_free_memory_cache(&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,
 				mmu_page_header_cache);
@@ -444,15 +446,15 @@ static void mmu_free_pte_chain(struct kvm_pte_chain *pc)
 	kmem_cache_free(pte_chain_cache, pc);
 }
 
-static struct kvm_rmap_desc *mmu_alloc_rmap_desc(struct kvm_vcpu *vcpu)
+static struct pte_list_desc *mmu_alloc_pte_list_desc(struct kvm_vcpu *vcpu)
 {
-	return mmu_memory_cache_alloc(&vcpu->arch.mmu_rmap_desc_cache,
-				      sizeof(struct kvm_rmap_desc));
+	return mmu_memory_cache_alloc(&vcpu->arch.mmu_pte_list_desc_cache,
+				      sizeof(struct pte_list_desc));
 }
 
-static void mmu_free_rmap_desc(struct kvm_rmap_desc *rd)
+static void mmu_free_pte_list_desc(struct pte_list_desc *pte_list_desc)
 {
-	kmem_cache_free(rmap_desc_cache, rd);
+	kmem_cache_free(pte_list_desc_cache, pte_list_desc);
 }
 
 static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index)
@@ -590,67 +592,42 @@ static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn)
 }
 
 /*
- * Take gfn and return the reverse mapping to it.
- */
-
-static unsigned long *gfn_to_rmap(struct kvm *kvm, gfn_t gfn, int level)
-{
-	struct kvm_memory_slot *slot;
-	struct kvm_lpage_info *linfo;
-
-	slot = gfn_to_memslot(kvm, gfn);
-	if (likely(level == PT_PAGE_TABLE_LEVEL))
-		return &slot->rmap[gfn - slot->base_gfn];
-
-	linfo = lpage_info_slot(gfn, slot, level);
-
-	return &linfo->rmap_pde;
-}
-
-/*
- * Reverse mapping data structures:
+ * Pte mapping structures:
  *
- * If rmapp bit zero is zero, then rmapp point to the shadw page table entry
- * that points to page_address(page).
+ * If pte_list bit zero is zero, then pte_list point to the spte.
  *
- * If rmapp bit zero is one, (then rmap & ~1) points to a struct kvm_rmap_desc
- * containing more mappings.
+ * If pte_list bit zero is one, (then pte_list & ~1) points to a struct
+ * pte_list_desc containing more mappings.
  *
- * Returns the number of rmap entries before the spte was added or zero if
+ * Returns the number of pte entries before the spte was added or zero if
  * the spte was not added.
  *
  */
-static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
+static int pte_list_add(struct kvm_vcpu *vcpu, u64 *spte,
+			unsigned long *pte_list)
 {
-	struct kvm_mmu_page *sp;
-	struct kvm_rmap_desc *desc;
-	unsigned long *rmapp;
+	struct pte_list_desc *desc;
 	int i, count = 0;
 
-	if (!is_rmap_spte(*spte))
-		return count;
-	sp = page_header(__pa(spte));
-	kvm_mmu_page_set_gfn(sp, spte - sp->spt, gfn);
-	rmapp = gfn_to_rmap(vcpu->kvm, gfn, sp->role.level);
-	if (!*rmapp) {
-		rmap_printk("rmap_add: %p %llx 0->1\n", spte, *spte);
-		*rmapp = (unsigned long)spte;
-	} else if (!(*rmapp & 1)) {
-		rmap_printk("rmap_add: %p %llx 1->many\n", spte, *spte);
-		desc = mmu_alloc_rmap_desc(vcpu);
-		desc->sptes[0] = (u64 *)*rmapp;
+	if (!*pte_list) {
+		rmap_printk("pte_list_add: %p %llx 0->1\n", spte, *spte);
+		*pte_list = (unsigned long)spte;
+	} else if (!(*pte_list & 1)) {
+		rmap_printk("pte_list_add: %p %llx 1->many\n", spte, *spte);
+		desc = mmu_alloc_pte_list_desc(vcpu);
+		desc->sptes[0] = (u64 *)*pte_list;
 		desc->sptes[1] = spte;
-		*rmapp = (unsigned long)desc | 1;
+		*pte_list = (unsigned long)desc | 1;
 		++count;
 	} else {
-		rmap_printk("rmap_add: %p %llx many->many\n", spte, *spte);
-		desc = (struct kvm_rmap_desc *)(*rmapp & ~1ul);
-		while (desc->sptes[RMAP_EXT-1] && desc->more) {
+		rmap_printk("pte_list_add: %p %llx many->many\n", spte, *spte);
+		desc = (struct pte_list_desc *)(*pte_list & ~1ul);
+		while (desc->sptes[PTE_LIST_EXT-1] && desc->more) {
 			desc = desc->more;
-			count += RMAP_EXT;
+			count += PTE_LIST_EXT;
 		}
-		if (desc->sptes[RMAP_EXT-1]) {
-			desc->more = mmu_alloc_rmap_desc(vcpu);
+		if (desc->sptes[PTE_LIST_EXT-1]) {
+			desc->more = mmu_alloc_pte_list_desc(vcpu);
 			desc = desc->more;
 		}
 		for (i = 0; desc->sptes[i]; ++i)
@@ -660,59 +637,78 @@ static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
 	return count;
 }
 
-static void rmap_desc_remove_entry(unsigned long *rmapp,
-				   struct kvm_rmap_desc *desc,
-				   int i,
-				   struct kvm_rmap_desc *prev_desc)
+static u64 *pte_list_next(unsigned long *pte_list, u64 *spte)
+{
+	struct pte_list_desc *desc;
+	u64 *prev_spte;
+	int i;
+
+	if (!*pte_list)
+		return NULL;
+	else if (!(*pte_list & 1)) {
+		if (!spte)
+			return (u64 *)*pte_list;
+		return NULL;
+	}
+	desc = (struct pte_list_desc *)(*pte_list & ~1ul);
+	prev_spte = NULL;
+	while (desc) {
+		for (i = 0; i < PTE_LIST_EXT && desc->sptes[i]; ++i) {
+			if (prev_spte == spte)
+				return desc->sptes[i];
+			prev_spte = desc->sptes[i];
+		}
+		desc = desc->more;
+	}
+	return NULL;
+}
+
+static void
+pte_list_desc_remove_entry(unsigned long *pte_list, struct pte_list_desc *desc,
+			   int i, struct pte_list_desc *prev_desc)
 {
 	int j;
 
-	for (j = RMAP_EXT - 1; !desc->sptes[j] && j > i; --j)
+	for (j = PTE_LIST_EXT - 1; !desc->sptes[j] && j > i; --j)
 		;
 	desc->sptes[i] = desc->sptes[j];
 	desc->sptes[j] = NULL;
 	if (j != 0)
 		return;
 	if (!prev_desc && !desc->more)
-		*rmapp = (unsigned long)desc->sptes[0];
+		*pte_list = (unsigned long)desc->sptes[0];
 	else
 		if (prev_desc)
 			prev_desc->more = desc->more;
 		else
-			*rmapp = (unsigned long)desc->more | 1;
-	mmu_free_rmap_desc(desc);
+			*pte_list = (unsigned long)desc->more | 1;
+	mmu_free_pte_list_desc(desc);
 }
 
-static void rmap_remove(struct kvm *kvm, u64 *spte)
+static void pte_list_remove(u64 *spte, unsigned long *pte_list)
 {
-	struct kvm_rmap_desc *desc;
-	struct kvm_rmap_desc *prev_desc;
-	struct kvm_mmu_page *sp;
-	gfn_t gfn;
-	unsigned long *rmapp;
+	struct pte_list_desc *desc;
+	struct pte_list_desc *prev_desc;
 	int i;
 
-	sp = page_header(__pa(spte));
-	gfn = kvm_mmu_page_get_gfn(sp, spte - sp->spt);
-	rmapp = gfn_to_rmap(kvm, gfn, sp->role.level);
-	if (!*rmapp) {
-		printk(KERN_ERR "rmap_remove: %p 0->BUG\n", spte);
+	if (!*pte_list) {
+		printk(KERN_ERR "pte_list_remove: %p 0->BUG\n", spte);
 		BUG();
-	} else if (!(*rmapp & 1)) {
-		rmap_printk("rmap_remove:  %p 1->0\n", spte);
-		if ((u64 *)*rmapp != spte) {
-			printk(KERN_ERR "rmap_remove:  %p 1->BUG\n", spte);
+	} else if (!(*pte_list & 1)) {
+		rmap_printk("pte_list_remove:  %p 1->0\n", spte);
+		if ((u64 *)*pte_list != spte) {
+			printk(KERN_ERR "pte_list_remove:  %p 1->BUG\n", spte);
 			BUG();
 		}
-		*rmapp = 0;
+		*pte_list = 0;
 	} else {
-		rmap_printk("rmap_remove:  %p many->many\n", spte);
-		desc = (struct kvm_rmap_desc *)(*rmapp & ~1ul);
+		rmap_printk("pte_list_remove:  %p many->many\n", spte);
+		desc = (struct pte_list_desc *)(*pte_list & ~1ul);
 		prev_desc = NULL;
 		while (desc) {
-			for (i = 0; i < RMAP_EXT && desc->sptes[i]; ++i)
+			for (i = 0; i < PTE_LIST_EXT && desc->sptes[i]; ++i)
 				if (desc->sptes[i] == spte) {
-					rmap_desc_remove_entry(rmapp,
+					pte_list_desc_remove_entry(pte_list,
 							       desc, i,
 							       prev_desc);
 					return;
@@ -720,11 +716,59 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
 			prev_desc = desc;
 			desc = desc->more;
 		}
-		pr_err("rmap_remove: %p many->many\n", spte);
+		pr_err("pte_list_remove: %p many->many\n", spte);
 		BUG();
 	}
 }
 
+/*
+ * Take gfn and return the reverse mapping to it.
+ */
+static unsigned long *gfn_to_rmap(struct kvm *kvm, gfn_t gfn, int level)
+{
+	struct kvm_memory_slot *slot;
+	struct kvm_lpage_info *linfo;
+
+	slot = gfn_to_memslot(kvm, gfn);
+	if (likely(level == PT_PAGE_TABLE_LEVEL))
+		return &slot->rmap[gfn - slot->base_gfn];
+
+	linfo = lpage_info_slot(gfn, slot, level);
+
+	return &linfo->rmap_pde;
+}
+
+static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
+{
+	struct kvm_mmu_page *sp;
+	unsigned long *rmapp;
+
+	if (!is_rmap_spte(*spte))
+		return 0;
+
+	sp = page_header(__pa(spte));
+	kvm_mmu_page_set_gfn(sp, spte - sp->spt, gfn);
+	rmapp = gfn_to_rmap(vcpu->kvm, gfn, sp->role.level);
+	return pte_list_add(vcpu, spte, rmapp);
+}
+
+static u64 *rmap_next(struct kvm *kvm, unsigned long *rmapp, u64 *spte)
+{
+	return pte_list_next(rmapp, spte);
+}
+
+static void rmap_remove(struct kvm *kvm, u64 *spte)
+{
+	struct kvm_mmu_page *sp;
+	gfn_t gfn;
+	unsigned long *rmapp;
+
+	sp = page_header(__pa(spte));
+	gfn = kvm_mmu_page_get_gfn(sp, spte - sp->spt);
+	rmapp = gfn_to_rmap(kvm, gfn, sp->role.level);
+	pte_list_remove(spte, rmapp);
+}
+
 static int set_spte_track_bits(u64 *sptep, u64 new_spte)
 {
 	pfn_t pfn;
@@ -752,32 +796,6 @@ static void drop_spte(struct kvm *kvm, u64 *sptep, u64 new_spte)
 		rmap_remove(kvm, sptep);
 }
 
-static u64 *rmap_next(struct kvm *kvm, unsigned long *rmapp, u64 *spte)
-{
-	struct kvm_rmap_desc *desc;
-	u64 *prev_spte;
-	int i;
-
-	if (!*rmapp)
-		return NULL;
-	else if (!(*rmapp & 1)) {
-		if (!spte)
-			return (u64 *)*rmapp;
-		return NULL;
-	}
-	desc = (struct kvm_rmap_desc *)(*rmapp & ~1ul);
-	prev_spte = NULL;
-	while (desc) {
-		for (i = 0; i < RMAP_EXT && desc->sptes[i]; ++i) {
-			if (prev_spte == spte)
-				return desc->sptes[i];
-			prev_spte = desc->sptes[i];
-		}
-		desc = desc->more;
-	}
-	return NULL;
-}
-
 static int rmap_write_protect(struct kvm *kvm, u64 gfn)
 {
 	unsigned long *rmapp;
@@ -3600,8 +3618,8 @@ static void mmu_destroy_caches(void)
 {
 	if (pte_chain_cache)
 		kmem_cache_destroy(pte_chain_cache);
-	if (rmap_desc_cache)
-		kmem_cache_destroy(rmap_desc_cache);
+	if (pte_list_desc_cache)
+		kmem_cache_destroy(pte_list_desc_cache);
 	if (mmu_page_header_cache)
 		kmem_cache_destroy(mmu_page_header_cache);
 }
@@ -3613,10 +3631,10 @@ int kvm_mmu_module_init(void)
 					    0, 0, NULL);
 	if (!pte_chain_cache)
 		goto nomem;
-	rmap_desc_cache = kmem_cache_create("kvm_rmap_desc",
-					    sizeof(struct kvm_rmap_desc),
+	pte_list_desc_cache = kmem_cache_create("pte_list_desc",
+					    sizeof(struct pte_list_desc),
 					    0, 0, NULL);
-	if (!rmap_desc_cache)
+	if (!pte_list_desc_cache)
 		goto nomem;
 
 	mmu_page_header_cache = kmem_cache_create("kvm_mmu_page_header",
-- 
1.7.4.4

[PATCH v2 5/7] KVM: MMU: remove the arithmetic of parent pte rmap

[Xiao Guangrong]

Parent pte rmap and page rmap are very similar, so use the same arithmetic
for them

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/include/asm/kvm_host.h |    7 +--
 arch/x86/kvm/mmu.c              |  189 +++++++++-----------------------------
 2 files changed, 46 insertions(+), 150 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0d824e4..e8a68f8 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -227,14 +227,10 @@ struct kvm_mmu_page {
 	 * in this shadow page.
 	 */
 	DECLARE_BITMAP(slot_bitmap, KVM_MEMORY_SLOTS + KVM_PRIVATE_MEM_SLOTS);
-	bool multimapped;         /* More than one parent_pte? */
 	bool unsync;
 	int root_count;          /* Currently serving as active root */
 	unsigned int unsync_children;
-	union {
-		u64 *parent_pte;               /* !multimapped */
-		struct hlist_head parent_ptes; /* multimapped, kvm_pte_chain */
-	};
+	unsigned long parent_ptes;	/* Reverse mapping for parent_pte */
 	DECLARE_BITMAP(unsync_child_bitmap, 512);
 };
 
@@ -346,7 +342,6 @@ struct kvm_vcpu_arch {
 	 * put it here to avoid allocation */
 	struct kvm_pv_mmu_op_buffer mmu_op_buffer;
 
-	struct kvm_mmu_memory_cache mmu_pte_chain_cache;
 	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;
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 5ba347b..c0b16dd 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -182,9 +182,6 @@ struct kvm_shadow_walk_iterator {
 	     shadow_walk_okay(&(_walker));			\
 	     shadow_walk_next(&(_walker)))
 
-typedef void (*mmu_parent_walk_fn) (struct kvm_mmu_page *sp, u64 *spte);
-
-static struct kmem_cache *pte_chain_cache;
 static struct kmem_cache *pte_list_desc_cache;
 static struct kmem_cache *mmu_page_header_cache;
 static struct percpu_counter kvm_total_used_mmu_pages;
@@ -397,12 +394,8 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
 {
 	int r;
 
-	r = mmu_topup_memory_cache(&vcpu->arch.mmu_pte_chain_cache,
-				   pte_chain_cache, 4);
-	if (r)
-		goto out;
 	r = mmu_topup_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache,
-				   pte_list_desc_cache, 4 + PTE_PREFETCH_NUM);
+				   pte_list_desc_cache, 8 + PTE_PREFETCH_NUM);
 	if (r)
 		goto out;
 	r = mmu_topup_memory_cache_page(&vcpu->arch.mmu_page_cache, 8);
@@ -416,8 +409,6 @@ out:
 
 static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
 {
-	mmu_free_memory_cache(&vcpu->arch.mmu_pte_chain_cache,
-				pte_chain_cache);
 	mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache,
 				pte_list_desc_cache);
 	mmu_free_memory_cache_page(&vcpu->arch.mmu_page_cache);
@@ -435,17 +426,6 @@ static void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc,
 	return p;
 }
 
-static struct kvm_pte_chain *mmu_alloc_pte_chain(struct kvm_vcpu *vcpu)
-{
-	return mmu_memory_cache_alloc(&vcpu->arch.mmu_pte_chain_cache,
-				      sizeof(struct kvm_pte_chain));
-}
-
-static void mmu_free_pte_chain(struct kvm_pte_chain *pc)
-{
-	kmem_cache_free(pte_chain_cache, pc);
-}
-
 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,
@@ -721,6 +701,26 @@ static void pte_list_remove(u64 *spte, unsigned long *pte_list)
 	}
 }
 
+typedef void (*pte_list_walk_fn) (u64 *spte);
+static void pte_list_walk(unsigned long *pte_list, pte_list_walk_fn fn)
+{
+	struct pte_list_desc *desc;
+	int i;
+
+	if (!*pte_list)
+		return;
+
+	if (!(*pte_list & 1))
+		return fn((u64 *)*pte_list);
+
+	desc = (struct pte_list_desc *)(*pte_list & ~1ul);
+	while (desc) {
+		for (i = 0; i < PTE_LIST_EXT && desc->sptes[i]; ++i)
+			fn(desc->sptes[i]);
+		desc = desc->more;
+	}
+}
+
 /*
  * Take gfn and return the reverse mapping to it.
  */
@@ -1069,134 +1069,52 @@ static unsigned kvm_page_table_hashfn(gfn_t gfn)
 	return gfn & ((1 << KVM_MMU_HASH_SHIFT) - 1);
 }
 
-static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
-					       u64 *parent_pte, int direct)
-{
-	struct kvm_mmu_page *sp;
-
-	sp = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache, sizeof *sp);
-	sp->spt = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache, PAGE_SIZE);
-	if (!direct)
-		sp->gfns = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache,
-						  PAGE_SIZE);
-	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
-	list_add(&sp->link, &vcpu->kvm->arch.active_mmu_pages);
-	bitmap_zero(sp->slot_bitmap, KVM_MEMORY_SLOTS + KVM_PRIVATE_MEM_SLOTS);
-	sp->multimapped = 0;
-	sp->parent_pte = parent_pte;
-	kvm_mod_used_mmu_pages(vcpu->kvm, +1);
-	return sp;
-}
-
 static void mmu_page_add_parent_pte(struct kvm_vcpu *vcpu,
 				    struct kvm_mmu_page *sp, u64 *parent_pte)
 {
-	struct kvm_pte_chain *pte_chain;
-	struct hlist_node *node;
-	int i;
-
 	if (!parent_pte)
 		return;
-	if (!sp->multimapped) {
-		u64 *old = sp->parent_pte;
 
-		if (!old) {
-			sp->parent_pte = parent_pte;
-			return;
-		}
-		sp->multimapped = 1;
-		pte_chain = mmu_alloc_pte_chain(vcpu);
-		INIT_HLIST_HEAD(&sp->parent_ptes);
-		hlist_add_head(&pte_chain->link, &sp->parent_ptes);
-		pte_chain->parent_ptes[0] = old;
-	}
-	hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link) {
-		if (pte_chain->parent_ptes[NR_PTE_CHAIN_ENTRIES-1])
-			continue;
-		for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i)
-			if (!pte_chain->parent_ptes[i]) {
-				pte_chain->parent_ptes[i] = parent_pte;
-				return;
-			}
-	}
-	pte_chain = mmu_alloc_pte_chain(vcpu);
-	BUG_ON(!pte_chain);
-	hlist_add_head(&pte_chain->link, &sp->parent_ptes);
-	pte_chain->parent_ptes[0] = parent_pte;
+	pte_list_add(vcpu, parent_pte, &sp->parent_ptes);
 }
 
 static void mmu_page_remove_parent_pte(struct kvm_mmu_page *sp,
 				       u64 *parent_pte)
 {
-	struct kvm_pte_chain *pte_chain;
-	struct hlist_node *node;
-	int i;
-
-	if (!sp->multimapped) {
-		BUG_ON(sp->parent_pte != parent_pte);
-		sp->parent_pte = NULL;
-		return;
-	}
-	hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link)
-		for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i) {
-			if (!pte_chain->parent_ptes[i])
-				break;
-			if (pte_chain->parent_ptes[i] != parent_pte)
-				continue;
-			while (i + 1 < NR_PTE_CHAIN_ENTRIES
-				&& pte_chain->parent_ptes[i + 1]) {
-				pte_chain->parent_ptes[i]
-					= pte_chain->parent_ptes[i + 1];
-				++i;
-			}
-			pte_chain->parent_ptes[i] = NULL;
-			if (i == 0) {
-				hlist_del(&pte_chain->link);
-				mmu_free_pte_chain(pte_chain);
-				if (hlist_empty(&sp->parent_ptes)) {
-					sp->multimapped = 0;
-					sp->parent_pte = NULL;
-				}
-			}
-			return;
-		}
-	BUG();
+	pte_list_remove(parent_pte, &sp->parent_ptes);
 }
 
-static void mmu_parent_walk(struct kvm_mmu_page *sp, mmu_parent_walk_fn fn)
+static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
+					       u64 *parent_pte, int direct)
 {
-	struct kvm_pte_chain *pte_chain;
-	struct hlist_node *node;
-	struct kvm_mmu_page *parent_sp;
-	int i;
-
-	if (!sp->multimapped && sp->parent_pte) {
-		parent_sp = page_header(__pa(sp->parent_pte));
-		fn(parent_sp, sp->parent_pte);
-		return;
-	}
-
-	hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link)
-		for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i) {
-			u64 *spte = pte_chain->parent_ptes[i];
-
-			if (!spte)
-				break;
-			parent_sp = page_header(__pa(spte));
-			fn(parent_sp, spte);
-		}
+	struct kvm_mmu_page *sp;
+	sp = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache,
+					sizeof *sp);
+	sp->spt = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache, PAGE_SIZE);
+	if (!direct)
+		sp->gfns = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache,
+						  PAGE_SIZE);
+	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
+	list_add(&sp->link, &vcpu->kvm->arch.active_mmu_pages);
+	bitmap_zero(sp->slot_bitmap, KVM_MEMORY_SLOTS + KVM_PRIVATE_MEM_SLOTS);
+	sp->parent_ptes = 0;
+	mmu_page_add_parent_pte(vcpu, sp, parent_pte);
+	kvm_mod_used_mmu_pages(vcpu->kvm, +1);
+	return sp;
 }
 
-static void mark_unsync(struct kvm_mmu_page *sp, u64 *spte);
+static void mark_unsync(u64 *spte);
 static void kvm_mmu_mark_parents_unsync(struct kvm_mmu_page *sp)
 {
-	mmu_parent_walk(sp, mark_unsync);
+	pte_list_walk(&sp->parent_ptes, mark_unsync);
 }
 
-static void mark_unsync(struct kvm_mmu_page *sp, u64 *spte)
+static void mark_unsync(u64 *spte)
 {
+	struct kvm_mmu_page *sp;
 	unsigned int index;
 
+	sp = page_header(__pa(spte));
 	index = spte - sp->spt;
 	if (__test_and_set_bit(index, sp->unsync_child_bitmap))
 		return;
@@ -1694,17 +1612,7 @@ static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
 {
 	u64 *parent_pte;
 
-	while (sp->multimapped || sp->parent_pte) {
-		if (!sp->multimapped)
-			parent_pte = sp->parent_pte;
-		else {
-			struct kvm_pte_chain *chain;
-
-			chain = container_of(sp->parent_ptes.first,
-					     struct kvm_pte_chain, link);
-			parent_pte = chain->parent_ptes[0];
-		}
-		BUG_ON(!parent_pte);
+	while ((parent_pte = pte_list_next(&sp->parent_ptes, NULL))) {
 		kvm_mmu_put_page(sp, parent_pte);
 		__set_spte(parent_pte, shadow_trap_nonpresent_pte);
 	}
@@ -3616,8 +3524,6 @@ static struct shrinker mmu_shrinker = {
 
 static void mmu_destroy_caches(void)
 {
-	if (pte_chain_cache)
-		kmem_cache_destroy(pte_chain_cache);
 	if (pte_list_desc_cache)
 		kmem_cache_destroy(pte_list_desc_cache);
 	if (mmu_page_header_cache)
@@ -3626,11 +3532,6 @@ static void mmu_destroy_caches(void)
 
 int kvm_mmu_module_init(void)
 {
-	pte_chain_cache = kmem_cache_create("kvm_pte_chain",
-					    sizeof(struct kvm_pte_chain),
-					    0, 0, NULL);
-	if (!pte_chain_cache)
-		goto nomem;
 	pte_list_desc_cache = kmem_cache_create("pte_list_desc",
 					    sizeof(struct pte_list_desc),
 					    0, 0, NULL);
-- 
1.7.4.4

[PATCH v2 6/7] KVM: MMU: cleanup for kvm_mmu_page_unlink_children

[Xiao Guangrong]

Cleanup the same operation between kvm_mmu_page_unlink_children and
mmu_pte_write_zap_pte

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/kvm/mmu.c |   66 ++++++++++++++++++---------------------------------
 1 files changed, 23 insertions(+), 43 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index c0b16dd..3fab3c2 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1566,32 +1566,33 @@ static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 	}
 }
 
+static void mmu_page_zap_pte(struct kvm *kvm, struct kvm_mmu_page *sp,
+			     u64 *spte)
+{
+	u64 pte;
+	struct kvm_mmu_page *child;
+
+	pte = *spte;
+	if (is_shadow_present_pte(pte)) {
+		if (is_last_spte(pte, sp->role.level))
+			drop_spte(kvm, spte, shadow_trap_nonpresent_pte);
+		else {
+			child = page_header(pte & PT64_BASE_ADDR_MASK);
+			mmu_page_remove_parent_pte(child, spte);
+		}
+	}
+	__set_spte(spte, shadow_trap_nonpresent_pte);
+	if (is_large_pte(pte))
+		--kvm->stat.lpages;
+}
+
 static void kvm_mmu_page_unlink_children(struct kvm *kvm,
 					 struct kvm_mmu_page *sp)
 {
 	unsigned i;
-	u64 *pt;
-	u64 ent;
-
-	pt = sp->spt;
 
-	for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
-		ent = pt[i];
-
-		if (is_shadow_present_pte(ent)) {
-			if (!is_last_spte(ent, sp->role.level)) {
-				ent &= PT64_BASE_ADDR_MASK;
-				mmu_page_remove_parent_pte(page_header(ent),
-							   &pt[i]);
-			} else {
-				if (is_large_pte(ent))
-					--kvm->stat.lpages;
-				drop_spte(kvm, &pt[i],
-					  shadow_trap_nonpresent_pte);
-			}
-		}
-		pt[i] = shadow_trap_nonpresent_pte;
-	}
+	for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
+		mmu_page_zap_pte(kvm, sp, sp->spt + i);
 }
 
 static void kvm_mmu_put_page(struct kvm_mmu_page *sp, u64 *parent_pte)
@@ -3069,27 +3070,6 @@ void kvm_mmu_unload(struct kvm_vcpu *vcpu)
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_unload);
 
-static void mmu_pte_write_zap_pte(struct kvm_vcpu *vcpu,
-				  struct kvm_mmu_page *sp,
-				  u64 *spte)
-{
-	u64 pte;
-	struct kvm_mmu_page *child;
-
-	pte = *spte;
-	if (is_shadow_present_pte(pte)) {
-		if (is_last_spte(pte, sp->role.level))
-			drop_spte(vcpu->kvm, spte, shadow_trap_nonpresent_pte);
-		else {
-			child = page_header(pte & PT64_BASE_ADDR_MASK);
-			mmu_page_remove_parent_pte(child, spte);
-		}
-	}
-	__set_spte(spte, shadow_trap_nonpresent_pte);
-	if (is_large_pte(pte))
-		--vcpu->kvm->stat.lpages;
-}
-
 static void mmu_pte_write_new_pte(struct kvm_vcpu *vcpu,
 				  struct kvm_mmu_page *sp, u64 *spte,
 				  const void *new)
@@ -3271,7 +3251,7 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
 		spte = &sp->spt[page_offset / sizeof(*spte)];
 		while (npte--) {
 			entry = *spte;
-			mmu_pte_write_zap_pte(vcpu, sp, spte);
+			mmu_page_zap_pte(vcpu->kvm, sp, spte);
 			if (gentry &&
 			      !((sp->role.word ^ vcpu->arch.mmu.base_role.word)
 			      & mask.word))
-- 
1.7.4.4

[PATCH v2 7/7] KVM: MMU: cleanup for dropping parent pte

[Xiao Guangrong]

Introduce drop_parent_pte to remove the rmap of parent pte and
clear parent pte

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/kvm/mmu.c |   21 ++++++++++++---------
 1 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 3fab3c2..2d14434 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1084,6 +1084,13 @@ static void mmu_page_remove_parent_pte(struct kvm_mmu_page *sp,
 	pte_list_remove(parent_pte, &sp->parent_ptes);
 }
 
+static void drop_parent_pte(struct kvm_mmu_page *sp,
+			    u64 *parent_pte)
+{
+	mmu_page_remove_parent_pte(sp, parent_pte);
+	__set_spte(parent_pte, shadow_trap_nonpresent_pte);
+}
+
 static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
 					       u64 *parent_pte, int direct)
 {
@@ -1560,8 +1567,7 @@ static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 		if (child->role.access == direct_access)
 			return;
 
-		mmu_page_remove_parent_pte(child, sptep);
-		__set_spte(sptep, shadow_trap_nonpresent_pte);
+		drop_parent_pte(child, sptep);
 		kvm_flush_remote_tlbs(vcpu->kvm);
 	}
 }
@@ -1578,7 +1584,7 @@ static void mmu_page_zap_pte(struct kvm *kvm, struct kvm_mmu_page *sp,
 			drop_spte(kvm, spte, shadow_trap_nonpresent_pte);
 		else {
 			child = page_header(pte & PT64_BASE_ADDR_MASK);
-			mmu_page_remove_parent_pte(child, spte);
+			drop_parent_pte(child, spte);
 		}
 	}
 	__set_spte(spte, shadow_trap_nonpresent_pte);
@@ -1613,10 +1619,8 @@ static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
 {
 	u64 *parent_pte;
 
-	while ((parent_pte = pte_list_next(&sp->parent_ptes, NULL))) {
-		kvm_mmu_put_page(sp, parent_pte);
-		__set_spte(parent_pte, shadow_trap_nonpresent_pte);
-	}
+	while ((parent_pte = pte_list_next(&sp->parent_ptes, NULL)))
+		drop_parent_pte(sp, parent_pte);
 }
 
 static int mmu_zap_unsync_children(struct kvm *kvm,
@@ -2046,8 +2050,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 			u64 pte = *sptep;
 
 			child = page_header(pte & PT64_BASE_ADDR_MASK);
-			mmu_page_remove_parent_pte(child, sptep);
-			__set_spte(sptep, shadow_trap_nonpresent_pte);
+			drop_parent_pte(child, sptep);
 			kvm_flush_remote_tlbs(vcpu->kvm);
 		} else if (pfn != spte_to_pfn(*sptep)) {
 			pgprintk("hfn old %llx new %llx\n",
-- 
1.7.4.4

Re: [PATCH v2 1/7] KVM: MMU: optimize pte write path if don't have protected sp

[Avi Kivity]

On 05/15/2011 06:20 PM, Xiao Guangrong wrote:
> Simply return from kvm_mmu_pte_write path if no shadow page is
> write-protected, then we can avoid to walk all shadow pages and hold
> mmu-lock

Patchset looks like a very good cleanup (plus the nice optimization in 
patch 1).

-- 
error compiling committee.c: too many arguments to function

Re: [PATCH v2 1/7] KVM: MMU: optimize pte write path if don't have protected sp

[Marcelo Tosatti]

On Mon, May 16, 2011 at 02:25:02PM +0300, Avi Kivity wrote:
> On 05/15/2011 06:20 PM, Xiao Guangrong wrote:
> >Simply return from kvm_mmu_pte_write path if no shadow page is
> >write-protected, then we can avoid to walk all shadow pages and hold
> >mmu-lock
> 
> Patchset looks like a very good cleanup (plus the nice optimization
> in patch 1).

What case is patch 1 optimizing for?

Re: [PATCH v2 1/7] KVM: MMU: optimize pte write path if don't have protected sp

[Avi Kivity]

On 05/18/2011 04:12 PM, Marcelo Tosatti wrote:
> On Mon, May 16, 2011 at 02:25:02PM +0300, Avi Kivity wrote:
> >  On 05/15/2011 06:20 PM, Xiao Guangrong wrote:
> >  >Simply return from kvm_mmu_pte_write path if no shadow page is
> >  >write-protected, then we can avoid to walk all shadow pages and hold
> >  >mmu-lock
> >
> >  Patchset looks like a very good cleanup (plus the nice optimization
> >  in patch 1).
>
> What case is patch 1 optimizing for?
>

Say, kvmclock updates.

-- 
error compiling committee.c: too many arguments to function

Re: [PATCH v2 1/7] KVM: MMU: optimize pte write path if don't have protected sp

[Marcelo Tosatti]

On Sun, May 15, 2011 at 11:20:27PM +0800, Xiao Guangrong wrote:
> Simply return from kvm_mmu_pte_write path if no shadow page is
> write-protected, then we can avoid to walk all shadow pages and hold
> mmu-lock
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>

Applied, thanks.