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KVM: MMU: dont hold pagecount reference for mapped sptes pages

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When using mmu notifiers, we are allowed to remove the page count
reference tooken by get_user_pages to a specific page that is mapped
inside the shadow page tables.

This is needed so we can balance the pagecount against mapcount
checking.

(Right now kvm increase the pagecount and does not increase the
mapcount when mapping page into shadow page table entry,
so when comparing pagecount against mapcount, you have no
reliable result.)

Signed-off-by: Izik Eidus <ieidus@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Izik Eidus 2009-09-23 21:47:16 +03:00 committed by Avi Kivity
parent 6a54435560
commit acb66dd051
1 changed files with 2 additions and 5 deletions
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7
arch/x86/kvm/mmu.c
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@ -634,9 +634,7 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
if (*spte & shadow_accessed_mask)
kvm_set_pfn_accessed(pfn);
if (is_writeble_pte(*spte))
kvm_release_pfn_dirty(pfn);
else
kvm_release_pfn_clean(pfn);
kvm_set_pfn_dirty(pfn);
rmapp = gfn_to_rmap(kvm, sp->gfns[spte - sp->spt], sp->role.level);
if (!*rmapp) {
printk(KERN_ERR "rmap_remove: %p %llx 0->BUG\n", spte, *spte);
@ -1877,8 +1875,7 @@ 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);
if (!is_rmap_spte(*sptep))
kvm_release_pfn_clean(pfn);
kvm_release_pfn_clean(pfn);
if (rmap_count > RMAP_RECYCLE_THRESHOLD)
rmap_recycle(vcpu, sptep, gfn);
} else {