This is a note to let you know that I've just added the patch titled KVM: SVM: Don't kill SEV guest if SMAP erratum triggers in usermode to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-svm-don-t-kill-sev-guest-if-smap-erratum-trigger.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 1618adc21bebbe4b6c91efad69b2c48f44535319 Author: Sean Christopherson <seanjc@xxxxxxxxxx> Date: Thu Jan 20 01:07:19 2022 +0000 KVM: SVM: Don't kill SEV guest if SMAP erratum triggers in usermode [ Upstream commit cdf85e0c5dc766fc7fc779466280e454a6d04f87 ] 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@xxxxxxxxxx> Reviewed-by: Liam Merwick <liam.merwick@xxxxxxxxxx> Message-Id: <20220120010719.711476-10-seanjc@xxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 980abc437cdaa..f05aa7290267d 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4473,7 +4473,21 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, void *insn, int i 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); } return false;