linux-kernel - [PATCH v2 08/11] KVM: MMU: use page track for non-leaf shadow pages

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Message-Id: <1450869954-30273-9-git-send-email-guangrong.xiao@linux.intel.com>
Date:	Wed, 23 Dec 2015 19:25:51 +0800
From:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
To:	pbonzini@...hat.com
Cc:	gleb@...nel.org, mtosatti@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, kai.huang@...ux.intel.com,
	jike.song@...el.com,
	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
Subject: [PATCH v2 08/11] KVM: MMU: use page track for non-leaf shadow pages

non-leaf shadow pages are always write protected, it can be the user
of page track

Signed-off-by: Xiao Guangrong <guangrong.xiao@...ux.intel.com>
---
 arch/x86/kvm/mmu.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index b23f9fc..5a2ca73 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -806,11 +806,17 @@ static void account_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
 	struct kvm_memory_slot *slot;
 	gfn_t gfn;
 
+	kvm->arch.indirect_shadow_pages++;
 	gfn = sp->gfn;
 	slots = kvm_memslots_for_spte_role(kvm, sp->role);
 	slot = __gfn_to_memslot(slots, gfn);
+
+	/* the non-leaf shadow pages are keeping readonly. */
+	if (sp->role.level > PT_PAGE_TABLE_LEVEL)
+		return kvm_slot_page_track_add_page_nolock(kvm, slot, gfn,
+							KVM_PAGE_TRACK_WRITE);
+
 	kvm_mmu_gfn_disallow_lpage(slot, gfn);
-	kvm->arch.indirect_shadow_pages++;
 }
 
 static void unaccount_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
@@ -819,11 +825,15 @@ static void unaccount_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
 	struct kvm_memory_slot *slot;
 	gfn_t gfn;
 
+	kvm->arch.indirect_shadow_pages--;
 	gfn = sp->gfn;
 	slots = kvm_memslots_for_spte_role(kvm, sp->role);
 	slot = __gfn_to_memslot(slots, gfn);
+	if (sp->role.level > PT_PAGE_TABLE_LEVEL)
+		return kvm_slot_page_track_remove_page_nolock(kvm, slot, gfn,
+							KVM_PAGE_TRACK_WRITE);
+
 	kvm_mmu_gfn_allow_lpage(slot, gfn);
-	kvm->arch.indirect_shadow_pages--;
 }
 
 static bool __mmu_gfn_lpage_is_disallowed(gfn_t gfn, int level,
@@ -2140,12 +2150,18 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
 	hlist_add_head(&sp->hash_link,
 		&vcpu->kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)]);
 	if (!direct) {
-		if (rmap_write_protect(vcpu, gfn))
+		/*
+		 * we should do write protection before syncing pages
+		 * otherwise the content of the synced shadow page may
+		 * be inconsistent with guest page table.
+		 */
+		account_shadowed(vcpu->kvm, sp);
+
+		if (level == PT_PAGE_TABLE_LEVEL &&
+		      rmap_write_protect(vcpu, gfn))
 			kvm_flush_remote_tlbs(vcpu->kvm);
 		if (level > PT_PAGE_TABLE_LEVEL && need_sync)
 			kvm_sync_pages(vcpu, gfn);
-
-		account_shadowed(vcpu->kvm, sp);
 	}
 	sp->mmu_valid_gen = vcpu->kvm->arch.mmu_valid_gen;
 	init_shadow_page_table(sp);
-- 
1.8.3.1

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