On 3/19/20 3:05 AM, Paolo Bonzini wrote:
On 18/03/20 19:40, Krish Sadhukhan wrote:
On 3/18/20 5:41 AM, Paolo Bonzini wrote:
EFER is set for L2 using svm_set_efer, which hardcodes EFER_SVME to 1
and hides
an incorrect value for EFER.SVME in the L1 VMCB. Perform the check
manually
to detect invalid guest state.
Reported-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/svm.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 08568ae9f7a1..2125c6ae5951 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3558,6 +3558,9 @@ static bool nested_svm_vmrun_msrpm(struct
vcpu_svm *svm)
static bool nested_vmcb_checks(struct vmcb *vmcb)
{
+ if ((vmcb->save.efer & EFER_SVME) == 0)
+ return false;
+
if ((vmcb->control.intercept & (1ULL << INTERCEPT_VMRUN)) == 0)
return false;
Ah! This now tells me that I forgot the KVM fix that was supposed to
accompany my patchset.
Heh, indeed. I was puzzled for a second after applying it, then decided
I would just fix it myself. :)
Do we need this check in software ? I wasn't checking the bit in KVM and
instead I was just making sure that L0 sets that bit based on the
setting in nested vmcb:
Thanks !
The only effect of the function below over svm_set_efer is to guarantee
a vmrun error to happen. Doing the test in nested_vmcb_checks is more
consistent with other must-be-one bits such as the VMRUN intercept, and
it's also a smaller patch.
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
Paolo
+static void nested_svm_set_efer(struct kvm_vcpu *vcpu, u64
nested_vmcb_efer)
+{
+ svm_set_efer(vcpu, nested_vmcb_efer);
+
+ if (!(nested_vmcb_efer & EFER_SVME))
+ to_svm(vcpu)->vmcb->save.efer &= ~EFER_SVME;
+}
+
static int is_external_interrupt(u32 info)
{
info &= SVM_EVTINJ_TYPE_MASK | SVM_EVTINJ_VALID;
@@ -3554,7 +3562,7 @@ static void enter_svm_guest_mode(struct vcpu_svm
*svm, u64
svm->vmcb->save.gdtr = nested_vmcb->save.gdtr;
svm->vmcb->save.idtr = nested_vmcb->save.idtr;
kvm_set_rflags(&svm->vcpu, nested_vmcb->save.rflags);
- svm_set_efer(&svm->vcpu, nested_vmcb->save.efer);
+ nested_svm_set_efer(&svm->vcpu, nested_vmcb->save.efer);
svm_set_cr0(&svm->vcpu, nested_vmcb->save.cr0);
svm_set_cr4(&svm->vcpu, nested_vmcb->save.cr4);
if (npt_enabled) {
