[PATCH 6/9] KVM: SVM: WARN if KVM attempts emulation on #UD or #GP for SEV guests

[Sean Christopherson <seanjc@google.com>]

WARN if KVM attempts to emulate in response to #UD or #GP for SEV guests,
i.e. if KVM intercepts #UD or #GP, as emulation on any fault except #NPF
is impossible since KVM cannot read guest private memory to get the code
stream, and the CPU's DecodeAssists feature only provides the instruction
bytes on #NPF.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/svm/svm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 994224ae2731..ed2ca875b84b 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4267,6 +4267,9 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
 	if (!sev_guest(vcpu->kvm))
 		return true;
 
+	/* #UD and #GP should never be intercepted for SEV guests. */
+	WARN_ON_ONCE(emul_type & (EMULTYPE_TRAP_UD | EMULTYPE_VMWARE_GP));
+
 	/*
 	 * Emulation is impossible for SEV-ES guests as KVM doesn't have access
 	 * to guest register state.
-- 
2.34.1.703.g22d0c6ccf7-goog