From: Brijesh Singh <brijesh.singh@amd.com>
To: linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@suse.de>,
        Joerg Roedel <joro@8bytes.org>, "Michael S . Tsirkin" <mst@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        =?UTF-8?q?=5C=22Radim=20Kr=C4=8Dm=C3=A1=C5=99=5C=22?= 
        <rkrcmar@redhat.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Brijesh Singh <brijesh.singh@amd.com>
Subject: [RFC Part2 PATCH v3 25/26] KVM: SVM: Do not install #UD intercept when SEV is enabled
Date: Mon, 24 Jul 2017 15:03:02 -0500
Message-Id: <20170724200303.12197-26-brijesh.singh@amd.com>
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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, 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.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 arch/x86/kvm/svm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 64b9f60..4581d03 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1432,8 +1432,10 @@ static void init_vmcb(struct vcpu_svm *svm)
 		svm->vmcb->control.virt_ext |= VIRTUAL_VMLOAD_VMSAVE_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);
 
-- 
2.9.4