KVM: MMU: large page update_pte issue with non-PAE 32-bit guests (resend)
Marcelo Tosatti [Wed, 11 Jun 2008 23:32:40 +0000 (20:32 -0300)]
kvm_mmu_pte_write() does not handle 32-bit non-PAE large page backed
guests properly. It will instantiate two 2MB sptes pointing to the same
physical 2MB page when a guest large pte update is trapped.

Instead of duplicating code to handle this, disallow directory level
updates to happen through kvm_mmu_pte_write(), so the two 2MB sptes
emulating one guest 4MB pte can be correctly created by the page fault
handling path.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

arch/x86/kvm/mmu.c

index 9628091..baa6503 100644 (file)
@@ -1581,11 +1581,13 @@ static void mmu_pte_write_new_pte(struct kvm_vcpu *vcpu,
                                  u64 *spte,
                                  const void *new)
 {
-       if ((sp->role.level != PT_PAGE_TABLE_LEVEL)
-           && !vcpu->arch.update_pte.largepage) {
-               ++vcpu->kvm->stat.mmu_pde_zapped;
-               return;
-       }
+       if (sp->role.level != PT_PAGE_TABLE_LEVEL) {
+               if (!vcpu->arch.update_pte.largepage ||
+                   sp->role.glevels == PT32_ROOT_LEVEL) {
+                       ++vcpu->kvm->stat.mmu_pde_zapped;
+                       return;
+               }
+        }
 
        ++vcpu->kvm->stat.mmu_pte_updated;
        if (sp->role.glevels == PT32_ROOT_LEVEL)