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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>
hifive-unleashed-5.1
Avi Kivity 2007-01-05 16:36:51 -08:00 committed by Linus Torvalds
parent 86a5ba025d
commit 3bb65a22a4
2 changed files with 19 additions and 2 deletions
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1
drivers/kvm/kvm.h
View File

@ -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 */

20
drivers/kvm/mmu.c
View File

@ -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);