Skip to contentSkip to conversation

KVM: MMU: split kvm_sync_page() function

PATCH Applied Xiao Guangrong 2 participants 4 messages May 15, 2010 – May 19, 2010

Subsystems (3)
x86 KVM KVM x86
lore
Share & tools
lore

Xiao Guangrong

author
#0 lore raw

PATCH 1/3 KVM: MMU: split kvm_sync_page() function

Split kvm_sync_page() into kvm_sync_page() and kvm_sync_page_transient() to clarify the code address Avi's suggestion

kvm_sync_page_transient() function only update shadow page but not mark it sync and not write protect sp->gfn. it will be used by later patch

Signed-off-by Xiao Guangrong <[email protected]>
---
 arch/x86/kvm/mmu.c |   29 +++++++++++++++++++++++++----
 1 files changed, 25 insertions(+), 4 deletions(-)
arch/x86/kvm/mmu.c +25 -4
index 48ed42e..549255d 100644
@@ -1198,16 +1198,20 @@ static void kvm_unlink_unsync_page(struct kvm *kvm, struct kvm_mmu_page *sp)
 
 static int kvm_mmu_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp);
 
-static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
+static int __kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
+			   bool clear_unsync)
 {
 	if (sp->role.cr4_pae != !!is_pae(vcpu)) {
 		kvm_mmu_zap_page(vcpu->kvm, sp);
 		return 1;
 	}
 
-	if (rmap_write_protect(vcpu->kvm, sp->gfn))
-		kvm_flush_remote_tlbs(vcpu->kvm);
-	kvm_unlink_unsync_page(vcpu->kvm, sp);
+	if (clear_unsync) {
+		if (rmap_write_protect(vcpu->kvm, sp->gfn))
+			kvm_flush_remote_tlbs(vcpu->kvm);
+		kvm_unlink_unsync_page(vcpu->kvm, sp);
+	}
+
 	if (vcpu->arch.mmu.sync_page(vcpu, sp)) {
 		kvm_mmu_zap_page(vcpu->kvm, sp);
 		return 1;

@@ -1217,6 +1221,23 @@ static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
 	return 0;
 }
 
+static void mmu_convert_notrap(struct kvm_mmu_page *sp);
+static int kvm_sync_page_transient(struct kvm_vcpu *vcpu,
+				   struct kvm_mmu_page *sp)
+{
+	int ret;
+
+	ret = __kvm_sync_page(vcpu, sp, false);
+	if (!ret)
+		mmu_convert_notrap(sp);
+	return ret;
+}
+
+static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
+{
+	return __kvm_sync_page(vcpu, sp, true);
+}
+
 struct mmu_page_path {
 	struct kvm_mmu_page *parent[PT64_ROOT_LEVEL-1];
 	unsigned int idx[PT64_ROOT_LEVEL-1];
Signature · 1 line
1.6.1.2
author
#1 lore raw

PATCH 2/3 KVM: MMU: don't write-protect if have new mapping to unsync page

Two cases maybe happen in kvm_mmu_get_page() function:

- one case is, the goal sp is already in cache, if the sp is unsync, we only need update it to assure this mapping is valid, but not mark it sync and not write-protect sp->gfn since it not broke unsync rule(one shadow page for a gfn)

- another case is, the goal sp not existed, we need create a new sp for gfn, i.e, gfn (may)has another shadow page, to keep unsync rule, we should sync(mark sync and write-protect) gfn's unsync shadow page. After enabling multiple unsync shadows, we sync those shadow pages only when the new sp not allow to become unsync(also for the unsyc rule, the new rule is: allow all pte page become unsync)

Signed-off-by Xiao Guangrong <[email protected]>
---
 arch/x86/kvm/mmu.c |   18 ++++++++++++++----
 1 files changed, 14 insertions(+), 4 deletions(-)
arch/x86/kvm/mmu.c +14 -4
index 549255d..97c5217 100644
@@ -1336,7 +1336,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
 	unsigned index;
 	unsigned quadrant;
 	struct hlist_head *bucket;
-	struct kvm_mmu_page *sp;
+	struct kvm_mmu_page *sp, *unsync_sp = NULL;
 	struct hlist_node *node, *tmp;
 
 	role = vcpu->arch.mmu.base_role;

@@ -1355,20 +1355,30 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
 	hlist_for_each_entry_safe(sp, node, tmp, bucket, hash_link)
 		if (sp->gfn == gfn) {
 			if (sp->unsync)
-				if (kvm_sync_page(vcpu, sp))
-					continue;
+				unsync_sp = sp;
 
 			if (sp->role.word != role.word)
 				continue;
 
+			if (!direct && unsync_sp &&
+			      kvm_sync_page_transient(vcpu, unsync_sp)) {
+				unsync_sp = NULL;
+				break;
+			}
+
 			mmu_page_add_parent_pte(vcpu, sp, parent_pte);
 			if (sp->unsync_children) {
 				set_bit(KVM_REQ_MMU_SYNC, &vcpu->requests);
 				kvm_mmu_mark_parents_unsync(sp);
-			}
+			} else if (sp->unsync)
+				kvm_mmu_mark_parents_unsync(sp);
+
 			trace_kvm_mmu_get_page(sp, false);
 			return sp;
 		}
+	if (!direct && unsync_sp)
+		kvm_sync_page(vcpu, unsync_sp);
+
 	++vcpu->kvm->stat.mmu_cache_miss;
 	sp = kvm_mmu_alloc_page(vcpu, parent_pte);
 	if (!sp)
Signature · 1 line
1.6.1.2
author
#2 lore raw

PATCH 3/3 KVM: MMU: only update unsync page in invlpg path

Only unsync pages need updated at invlpg time since other shadow pages are write-protected

Signed-off-by Xiao Guangrong <[email protected]>
---
 arch/x86/kvm/paging_tmpl.h |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)
arch/x86/kvm/paging_tmpl.h +6 -2
index 71c73fe..dfbc8c7 100644
@@ -463,6 +463,7 @@ out_unlock:
 static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
 {
 	struct kvm_shadow_walk_iterator iterator;
+	struct kvm_mmu_page *sp;
 	gpa_t pte_gpa = -1;
 	int level;
 	u64 *sptep;

@@ -474,10 +475,13 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
 		level = iterator.level;
 		sptep = iterator.sptep;
 
+		sp = page_header(__pa(sptep));
 		if (is_last_spte(*sptep, level)) {
-			struct kvm_mmu_page *sp = page_header(__pa(sptep));
 			int offset, shift;
 
+			if (!sp->unsync)
+				break;
+
 			shift = PAGE_SHIFT -
 				  (PT_LEVEL_BITS - PT64_LEVEL_BITS) * level;
 			offset = sp->role.quadrant << shift;

@@ -495,7 +499,7 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
 			break;
 		}
 
-		if (!is_shadow_present_pte(*sptep))
+		if (!is_shadow_present_pte(*sptep) || !sp->unsync_children)
 			break;
 	}
Signature · 1 line
1.6.1.2
Applied
#3 lore raw
In reply to Xiao Guangrong
Quoted 6 lines · Xiao Guangrong

Split kvm_sync_page() into kvm_sync_page() and kvm_sync_page_transient() to clarify the code address Avi's suggestion

kvm_sync_page_transient() function only update shadow page but not mark it sync and not write protect sp->gfn. it will be used by later patch

Applied all three, thanks.

Signature · 1 line
Do not meddle in the internals of kernels, for they are subtle and quick to panic.