From 55467fcd55b89c622e62b4afe60ac0eb2fae91f2 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 20 Jan 2022 01:07:11 +0000 Subject: [PATCH] KVM: SVM: Never reject emulation due to SMAP errata for !SEV guests Always signal that emulation is possible for !SEV guests regardless of whether or not the CPU provided a valid instruction byte stream. KVM can read all guest state (memory and registers) for !SEV guests, i.e. can fetch the code stream from memory even if the CPU failed to do so because of the SMAP errata. Fixes: 05d5a4863525 ("KVM: SVM: Workaround errata#1096 (insn_len maybe zero on SMAP violation)") Cc: stable@vger.kernel.org Cc: Tom Lendacky Cc: Brijesh Singh Signed-off-by: Sean Christopherson Reviewed-by: Liam Merwick Message-Id: <20220120010719.711476-2-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/svm.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index ec05f8b..a46e1c6 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4258,8 +4258,13 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, void *insn, int i bool smep, smap, is_user; unsigned long cr4; + /* Emulation is always possible when KVM has access to all guest state. */ + if (!sev_guest(vcpu->kvm)) + return true; + /* - * When the guest is an SEV-ES guest, emulation is not possible. + * Emulation is impossible for SEV-ES guests as KVM doesn't have access + * to guest register state. */ if (sev_es_guest(vcpu->kvm)) return false; @@ -4319,9 +4324,6 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, void *insn, int i smap = cr4 & X86_CR4_SMAP; is_user = svm_get_cpl(vcpu) == 3; if (smap && (!smep || is_user)) { - if (!sev_guest(vcpu->kvm)) - return true; - pr_err_ratelimited("KVM: SEV Guest triggered AMD Erratum 1096\n"); kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu); } -- 2.7.4