[RFC PATCH v3 13/27] KVM: SVM: Warn if we ever receive AVIC_UNACCELERATED_ACCESS #VMEXIT

[Naveen N Rao (AMD)]

With Secure AVIC, all AVIC-related exits are NAE (Non-Automatic Exits)
and result in a #VC in the guest rather than a #VMEXIT. The guest can
then use GHCB to request specific services from the hypervisor. As such,
we should never see AVIC_UNACCELERATED_ACCESS exits in KVM. Add a
WARN_ON() so that it is clear that something is wrong.

Note that AVIC_INCOMPLETE_IPI is still possible via VMGEXIT.

Signed-off-by: Naveen N Rao (AMD) <naveen@xxxxxxxxxx>
---
 arch/x86/kvm/svm/avic.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index bfd758369b5a..bf701e604a85 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -896,6 +896,10 @@ int avic_unaccelerated_access_interception(struct kvm_vcpu *vcpu)
 
 	trace_kvm_avic_unaccelerated_access(vcpu->vcpu_id, offset,
 					    trap, write, vector);
+
+	if (WARN_ON_ONCE(snp_is_secure_avic_enabled(vcpu->kvm)))
+		return 1;
+
 	if (trap) {
 		/* Handling Trap */
 		WARN_ONCE(!write, "svm: Handling trap read.\n");
-- 
2.54.0