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@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: "Radim Krčmář" <rkrcmar@xxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
---
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 f350e9bac9eb..3e848f952b4f 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1443,8 +1443,10 @@ 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);
--
2.9.5
