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[PATCH] KVM: MMU: Never free a shadow page actively serving as a root
We always need cr3 to point to something valid, so if we detect that we're freeing a root page, simply push it back to the top of the active list. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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parent
86a5ba025d
commit
3bb65a22a4
2 changed files with 19 additions and 2 deletions
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@ -134,6 +134,7 @@ struct kvm_mmu_page {
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*/
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int global; /* Set if all ptes in this page are global */
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int multimapped; /* More than one parent_pte? */
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int root_count; /* Currently serving as active root */
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union {
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u64 *parent_pte; /* !multimapped */
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struct hlist_head parent_ptes; /* multimapped, kvm_pte_chain */
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@ -550,8 +550,13 @@ static void kvm_mmu_zap_page(struct kvm_vcpu *vcpu,
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*parent_pte = 0;
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}
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kvm_mmu_page_unlink_children(vcpu, page);
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hlist_del(&page->hash_link);
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kvm_mmu_free_page(vcpu, page->page_hpa);
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if (!page->root_count) {
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hlist_del(&page->hash_link);
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kvm_mmu_free_page(vcpu, page->page_hpa);
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} else {
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list_del(&page->link);
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list_add(&page->link, &vcpu->kvm->active_mmu_pages);
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}
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}
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static int kvm_mmu_unprotect_page(struct kvm_vcpu *vcpu, gfn_t gfn)
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@ -667,12 +672,15 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, hpa_t p)
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static void mmu_free_roots(struct kvm_vcpu *vcpu)
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{
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int i;
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struct kvm_mmu_page *page;
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#ifdef CONFIG_X86_64
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if (vcpu->mmu.shadow_root_level == PT64_ROOT_LEVEL) {
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hpa_t root = vcpu->mmu.root_hpa;
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ASSERT(VALID_PAGE(root));
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page = page_header(root);
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--page->root_count;
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vcpu->mmu.root_hpa = INVALID_PAGE;
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return;
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}
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@ -682,6 +690,8 @@ static void mmu_free_roots(struct kvm_vcpu *vcpu)
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ASSERT(VALID_PAGE(root));
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root &= PT64_BASE_ADDR_MASK;
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page = page_header(root);
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--page->root_count;
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vcpu->mmu.pae_root[i] = INVALID_PAGE;
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}
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vcpu->mmu.root_hpa = INVALID_PAGE;
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@ -691,6 +701,8 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu)
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{
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int i;
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gfn_t root_gfn;
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struct kvm_mmu_page *page;
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root_gfn = vcpu->cr3 >> PAGE_SHIFT;
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#ifdef CONFIG_X86_64
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@ -700,6 +712,8 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu)
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ASSERT(!VALID_PAGE(root));
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root = kvm_mmu_get_page(vcpu, root_gfn, 0,
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PT64_ROOT_LEVEL, 0, NULL)->page_hpa;
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page = page_header(root);
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++page->root_count;
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vcpu->mmu.root_hpa = root;
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return;
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}
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@ -715,6 +729,8 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu)
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root = kvm_mmu_get_page(vcpu, root_gfn, i << 30,
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PT32_ROOT_LEVEL, !is_paging(vcpu),
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NULL)->page_hpa;
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page = page_header(root);
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++page->root_count;
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vcpu->mmu.pae_root[i] = root | PT_PRESENT_MASK;
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}
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vcpu->mmu.root_hpa = __pa(vcpu->mmu.pae_root);
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