x86: kvm: mmu: use ept a/d in vmcs02 iff used in vmcs12
EPT A/D was enabled in the vmcs02 EPTP regardless of the vmcs12's EPTP
value. The problem is that enabling A/D changes the behavior of L2's
x86 page table walks as seen by L1. With A/D enabled, x86 page table
walks are always treated as EPT writes.
Commit ae1e2d1082ae ("kvm: nVMX: support EPT accessed/dirty bits",
2017-03-30) tried to work around this problem by clearing the write
bit in the exit qualification for EPT violations triggered by page
walks. However, that fixup introduced the opposite bug: page-table walks
that actually set x86 A/D bits were *missing* the write bit in the exit
qualification.
This patch fixes the problem by disabling EPT A/D in the shadow MMU
when EPT A/D is disabled in vmcs12's EPTP.
Signed-off-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 48d8e7e..3ba600d 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4419,6 +4419,7 @@
context->root_level = context->shadow_root_level;
context->root_hpa = INVALID_PAGE;
context->direct_map = false;
+ context->base_role.ad_disabled = !accessed_dirty;
update_permission_bitmask(vcpu, context, true);
update_pkru_bitmask(vcpu, context, true);