[Part2,v4,27/29] KVM: SVM: Do not install #UD intercept when SEV is enabled

Commit Message

Brijesh Singh Sept. 19, 2017, 8:46 p.m. UTC

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 <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: "H. Peter Anvin" <[e-mail]>
Cc: Paolo Bonzini <[e-mail]>
Cc: "Radim Krčmář" <[e-mail]>
Cc: Joerg Roedel <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Tom Lendacky <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Reviewed-by: Borislav Petkov <[e-mail]>
Signed-off-by: Brijesh Singh <[e-mail]>
---
 arch/x86/kvm/svm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Patch

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index b9906cb59238..d997f63c765d 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1437,8 +1437,10 @@  static void init_vmcb(struct vcpu_svm *svm)
 		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);