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Commit 9ed5520d authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Avi Kivity
Browse files

KVM: MMU: fix page dirty tracking lost while sync page 



In sync-page path, if spte.writable is changed, it will lose page dirty
tracking, for example:

assume spte.writable = 0 in a unsync-page, when it's synced, it map spte
to writable(that is spte.writable = 1), later guest write spte.gfn, it means
spte.gfn is dirty, then guest changed this mapping to read-only, after it's
synced,  spte.writable = 0

So, when host release the spte, it detect spte.writable = 0 and not mark page
dirty

Signed-off-by: default avatarXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent daa3db69

arch/x86/kvm/mmu.c

+3 −7
Original line number Diff line number Diff line
@@ -1985,6 +1985,8 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, 
		mark_page_dirty(vcpu->kvm, gfn);



set_pte:

	if (is_writable_pte(*sptep) && !is_writable_pte(spte))

		kvm_set_pfn_dirty(pfn);

	update_spte(sptep, spte);

done:

	return ret;
@@ -1998,7 +2000,6 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, 
			 bool reset_host_protection)

{

	int was_rmapped = 0;

	int was_writable = is_writable_pte(*sptep);

	int rmap_count;



	pgprintk("%s: spte %llx access %x write_fault %d"
@@ -2048,15 +2049,10 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, 
	page_header_update_slot(vcpu->kvm, sptep, gfn);

	if (!was_rmapped) {

		rmap_count = rmap_add(vcpu, sptep, gfn);

		kvm_release_pfn_clean(pfn);

		if (rmap_count > RMAP_RECYCLE_THRESHOLD)

			rmap_recycle(vcpu, sptep, gfn);

	} else {

		if (was_writable)

			kvm_release_pfn_dirty(pfn);

		else

			kvm_release_pfn_clean(pfn);

	}

	kvm_release_pfn_clean(pfn);

	if (speculative) {

		vcpu->arch.last_pte_updated = sptep;

		vcpu->arch.last_pte_gfn = gfn;