KVM: MMU: dont hold pagecount reference for mapped sptes pages (acb66dd0) · Commits · 戴 / test

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>

arch/x86/kvm/mmu.c

+2 −5

Original line number	Diff line number	Diff line
		@@ -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);
		@@ -1877,7 +1875,6 @@ 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);
		if (rmap_count > RMAP_RECYCLE_THRESHOLD)
		rmap_recycle(vcpu, sptep, gfn);

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