From: Brijesh Singh <brijesh.singh@amd.com>
Date: Mon, 4 Dec 2017 10:57:39 -0600
Subject: KVM: SVM: Do not install #UD intercept when SEV is enabled
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Git-commit: 35c6f649bbb2e3f367116307273f998f0bf3e08e
Patch-mainline: v4.16-rc1
References: bsc#1063068

On #UD, x86_emulate_instruction() fetches the data from guest memory and
decodes the instruction bytes to assist further. When SEV is enabled, the
instruction bytes will be encrypted using the guest-specific key and the
hypervisor will no longer able to fetch the instruction bytes to assist
UD handling. By not installing intercept we let the guest receive and
handle #UD.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Acked-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/kvm/svm.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1442,8 +1442,10 @@ static void init_vmcb(struct vcpu_svm *s
 		svm->vmcb->control.int_ctl |= V_GIF_ENABLE_MASK;
 	}
 
-	if (sev_guest(svm->vcpu.kvm))
+	if (sev_guest(svm->vcpu.kvm)) {
 		svm->vmcb->control.nested_ctl |= SVM_NESTED_CTL_SEV_ENABLE;
+		clr_exception_intercept(svm, UD_VECTOR);
+	}
 
 	mark_all_dirty(svm->vmcb);