From 3bb65a22a4502067f8cd3cb4c923ffa70be62091 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Fri, 5 Jan 2007 16:36:51 -0800 Subject: [PATCH] [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 Acked-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/kvm/kvm.h | 1 + drivers/kvm/mmu.c | 20 ++++++++++++++++++-- 2 files changed, 19 insertions(+), 2 deletions(-) diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h index 201b2735ca91..b24a86e1f434 100644 --- a/drivers/kvm/kvm.h +++ b/drivers/kvm/kvm.h @@ -134,6 +134,7 @@ struct kvm_mmu_page { */ int global; /* Set if all ptes in this page are global */ int multimapped; /* More than one parent_pte? */ + int root_count; /* Currently serving as active root */ union { u64 *parent_pte; /* !multimapped */ struct hlist_head parent_ptes; /* multimapped, kvm_pte_chain */ diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c index 0e44aca9eee7..f16321498093 100644 --- a/drivers/kvm/mmu.c +++ b/drivers/kvm/mmu.c @@ -550,8 +550,13 @@ static void kvm_mmu_zap_page(struct kvm_vcpu *vcpu, *parent_pte = 0; } kvm_mmu_page_unlink_children(vcpu, page); - hlist_del(&page->hash_link); - kvm_mmu_free_page(vcpu, page->page_hpa); + if (!page->root_count) { + hlist_del(&page->hash_link); + kvm_mmu_free_page(vcpu, page->page_hpa); + } else { + list_del(&page->link); + list_add(&page->link, &vcpu->kvm->active_mmu_pages); + } } static int kvm_mmu_unprotect_page(struct kvm_vcpu *vcpu, gfn_t gfn) @@ -667,12 +672,15 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, hpa_t p) static void mmu_free_roots(struct kvm_vcpu *vcpu) { int i; + struct kvm_mmu_page *page; #ifdef CONFIG_X86_64 if (vcpu->mmu.shadow_root_level == PT64_ROOT_LEVEL) { hpa_t root = vcpu->mmu.root_hpa; ASSERT(VALID_PAGE(root)); + page = page_header(root); + --page->root_count; vcpu->mmu.root_hpa = INVALID_PAGE; return; } @@ -682,6 +690,8 @@ static void mmu_free_roots(struct kvm_vcpu *vcpu) ASSERT(VALID_PAGE(root)); root &= PT64_BASE_ADDR_MASK; + page = page_header(root); + --page->root_count; vcpu->mmu.pae_root[i] = INVALID_PAGE; } vcpu->mmu.root_hpa = INVALID_PAGE; @@ -691,6 +701,8 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu) { int i; gfn_t root_gfn; + struct kvm_mmu_page *page; + root_gfn = vcpu->cr3 >> PAGE_SHIFT; #ifdef CONFIG_X86_64 @@ -700,6 +712,8 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu) ASSERT(!VALID_PAGE(root)); root = kvm_mmu_get_page(vcpu, root_gfn, 0, PT64_ROOT_LEVEL, 0, NULL)->page_hpa; + page = page_header(root); + ++page->root_count; vcpu->mmu.root_hpa = root; return; } @@ -715,6 +729,8 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu) root = kvm_mmu_get_page(vcpu, root_gfn, i << 30, PT32_ROOT_LEVEL, !is_paging(vcpu), NULL)->page_hpa; + page = page_header(root); + ++page->root_count; vcpu->mmu.pae_root[i] = root | PT_PRESENT_MASK; } vcpu->mmu.root_hpa = __pa(vcpu->mmu.pae_root); -- 2.20.1