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authorSean Christopherson <seanjc@google.com>2022-01-20 01:07:19 +0000
committerPaolo Bonzini <pbonzini@redhat.com>2022-01-26 12:15:02 -0500
commitcdf85e0c5dc766fc7fc779466280e454a6d04f87 (patch)
tree436f0d0cf7a1142c9edbe2c82d0ddce470d1d84c /arch/x86
parent3280cc22aea74d78ebbea277ff8bc8d593582de3 (diff)
downloadlinux-cdf85e0c5dc766fc7fc779466280e454a6d04f87.tar.bz2
KVM: SVM: Don't kill SEV guest if SMAP erratum triggers in usermode
Inject a #GP instead of synthesizing triple fault to try to avoid killing the guest if emulation of an SEV guest fails due to encountering the SMAP erratum. The injected #GP may still be fatal to the guest, e.g. if the userspace process is providing critical functionality, but KVM should make every attempt to keep the guest alive. Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Liam Merwick <liam.merwick@oracle.com> Message-Id: <20220120010719.711476-10-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kvm/svm/svm.c16
1 files changed, 15 insertions, 1 deletions
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index be25831830b0..f14f4ab97a80 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4360,7 +4360,21 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
is_user = svm_get_cpl(vcpu) == 3;
if (smap && (!smep || is_user)) {
pr_err_ratelimited("KVM: SEV Guest triggered AMD Erratum 1096\n");
- kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
+
+ /*
+ * If the fault occurred in userspace, arbitrarily inject #GP
+ * to avoid killing the guest and to hopefully avoid confusing
+ * the guest kernel too much, e.g. injecting #PF would not be
+ * coherent with respect to the guest's page tables. Request
+ * triple fault if the fault occurred in the kernel as there's
+ * no fault that KVM can inject without confusing the guest.
+ * In practice, the triple fault is moot as no sane SEV kernel
+ * will execute from user memory while also running with SMAP=1.
+ */
+ if (is_user)
+ kvm_inject_gp(vcpu, 0);
+ else
+ kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
}
resume_guest: