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[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: 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>
This commit is contained in:
Avi Kivity 2007-01-05 16:36:48 -08:00 committed by Linus Torvalds
parent 73f7198e73
commit 0e7bc4b961
1 changed files with 17 additions and 2 deletions
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19
drivers/kvm/mmu.c
View File

@ -954,21 +954,36 @@ void kvm_mmu_pre_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes)
gfn_t gfn = gpa >> PAGE_SHIFT;
struct kvm_mmu_page *page;
struct kvm_mmu_page *child;
struct hlist_node *node;
struct hlist_node *node, *n;
struct hlist_head *bucket;
unsigned index;
u64 *spte;
u64 pte;
unsigned offset = offset_in_page(gpa);
unsigned pte_size;
unsigned page_offset;
unsigned misaligned;
int level;
pgprintk("%s: gpa %llx bytes %d\n", __FUNCTION__, gpa, bytes);
index = kvm_page_table_hashfn(gfn) % KVM_NUM_MMU_PAGES;
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)
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;
level = page->role.level;
if (page->role.glevels == PT32_ROOT_LEVEL) {