KVM: MMU: large page update_pte issue with non-PAE 32-bit guests (resend)

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>

1 files changed, 7 insertions, 5 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 9628091c574d..baa6503894d3 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -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)