[PATCH] KVM: MMU: Zap shadow page table entries on writes to guest page tables

Iterate over all shadow pages which correspond to a the given guest page table
and remove the mappings.

A subsequent page fault will reestablish the new mapping.

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>

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index bce7eb2..6dbd83b 100644 (file)
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -958,7 +958,43 @@ int kvm_mmu_reset_context(struct kvm_vcpu *vcpu)
 
 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_head *bucket;
+       unsigned index;
+       u64 *spte;
+       u64 pte;
+       unsigned offset = offset_in_page(gpa);
+       unsigned page_offset;
+       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) {
+               if (page->gfn != gfn || page->role.metaphysical)
+                       continue;
+               page_offset = offset;
+               level = page->role.level;
+               if (page->role.glevels == PT32_ROOT_LEVEL) {
+                       page_offset <<= 1;          /* 32->64 */
+                       page_offset &= ~PAGE_MASK;
+               }
+               spte = __va(page->page_hpa);
+               spte += page_offset / sizeof(*spte);
+               pte = *spte;
+               if (is_present_pte(pte)) {
+                       if (level == PT_PAGE_TABLE_LEVEL)
+                               rmap_remove(vcpu->kvm, spte);
+                       else {
+                               child = page_header(pte & PT64_BASE_ADDR_MASK);
+                               mmu_page_remove_parent_pte(child, spte);
+                       }
+               }
+               *spte = 0;
+       }
 }
 
 void kvm_mmu_post_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes)