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

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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: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Xiao Guangrong 2010-07-16 11:25:17 +08:00 committed by Avi Kivity
parent daa3db693c
commit 9ed5520dd3
1 changed files with 3 additions and 7 deletions
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10
arch/x86/kvm/mmu.c
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@ -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;