Commit 0e7bc4b9 authored by Avi Kivity's avatar Avi Kivity Committed by Linus Torvalds

[PATCH] KVM: MMU: Handle misaligned accesses to write protected guest page tables

A misaligned access affects two shadow ptes instead of just one.

Since a misaligned access is unlikely to occur on a real page table, just zap
the page out of existence, avoiding further trouble.
Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 73f7198e
...@@ -954,21 +954,36 @@ void kvm_mmu_pre_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes) ...@@ -954,21 +954,36 @@ void kvm_mmu_pre_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes)
gfn_t gfn = gpa >> PAGE_SHIFT; gfn_t gfn = gpa >> PAGE_SHIFT;
struct kvm_mmu_page *page; struct kvm_mmu_page *page;
struct kvm_mmu_page *child; struct kvm_mmu_page *child;
struct hlist_node *node; struct hlist_node *node, *n;
struct hlist_head *bucket; struct hlist_head *bucket;
unsigned index; unsigned index;
u64 *spte; u64 *spte;
u64 pte; u64 pte;
unsigned offset = offset_in_page(gpa); unsigned offset = offset_in_page(gpa);
unsigned pte_size;
unsigned page_offset; unsigned page_offset;
unsigned misaligned;
int level; int level;
pgprintk("%s: gpa %llx bytes %d\n", __FUNCTION__, gpa, bytes); pgprintk("%s: gpa %llx bytes %d\n", __FUNCTION__, gpa, bytes);
index = kvm_page_table_hashfn(gfn) % KVM_NUM_MMU_PAGES; index = kvm_page_table_hashfn(gfn) % KVM_NUM_MMU_PAGES;
bucket = &vcpu->kvm->mmu_page_hash[index]; bucket = &vcpu->kvm->mmu_page_hash[index];
hlist_for_each_entry(page, node, bucket, hash_link) { hlist_for_each_entry_safe(page, node, n, bucket, hash_link) {
if (page->gfn != gfn || page->role.metaphysical) if (page->gfn != gfn || page->role.metaphysical)
continue; continue;
pte_size = page->role.glevels == PT32_ROOT_LEVEL ? 4 : 8;
misaligned = (offset ^ (offset + bytes - 1)) & ~(pte_size - 1);
if (misaligned) {
/*
* Misaligned accesses are too much trouble to fix
* up; also, they usually indicate a page is not used
* as a page table.
*/
pgprintk("misaligned: gpa %llx bytes %d role %x\n",
gpa, bytes, page->role.word);
kvm_mmu_zap_page(vcpu, page);
continue;
}
page_offset = offset; page_offset = offset;
level = page->role.level; level = page->role.level;
if (page->role.glevels == PT32_ROOT_LEVEL) { if (page->role.glevels == PT32_ROOT_LEVEL) {
......
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