KVM: MMU: ignore zapped root pagetables
Mark zapped root pagetables as invalid and ignore such pages during lookup.
This is a problem with the cr3-target feature, where a zapped root table fools
the faulting code into creating a read-only mapping. The result is a lockup
if the instruction can't be emulated.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f7541fe..103d008 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -667,7 +667,8 @@
index = kvm_page_table_hashfn(gfn);
bucket = &kvm->arch.mmu_page_hash[index];
hlist_for_each_entry(sp, node, bucket, hash_link)
- if (sp->gfn == gfn && !sp->role.metaphysical) {
+ if (sp->gfn == gfn && !sp->role.metaphysical
+ && !sp->role.invalid) {
pgprintk("%s: found role %x\n",
__FUNCTION__, sp->role.word);
return sp;
@@ -792,8 +793,11 @@
if (!sp->root_count) {
hlist_del(&sp->hash_link);
kvm_mmu_free_page(kvm, sp);
- } else
+ } else {
list_move(&sp->link, &kvm->arch.active_mmu_pages);
+ sp->role.invalid = 1;
+ kvm_reload_remote_mmus(kvm);
+ }
kvm_mmu_reset_last_pte_updated(kvm);
}
@@ -1073,6 +1077,8 @@
sp = page_header(root);
--sp->root_count;
+ if (!sp->root_count && sp->role.invalid)
+ kvm_mmu_zap_page(vcpu->kvm, sp);
vcpu->arch.mmu.root_hpa = INVALID_PAGE;
spin_unlock(&vcpu->kvm->mmu_lock);
return;
@@ -1085,6 +1091,8 @@
root &= PT64_BASE_ADDR_MASK;
sp = page_header(root);
--sp->root_count;
+ if (!sp->root_count && sp->role.invalid)
+ kvm_mmu_zap_page(vcpu->kvm, sp);
}
vcpu->arch.mmu.pae_root[i] = INVALID_PAGE;
}