From: Sean Christopherson seanjc@google.com
commit 55467fcd55b89c622e62b4afe60ac0eb2fae91f2 upstream.
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 thomas.lendacky@amd.com Cc: Brijesh Singh brijesh.singh@amd.com Signed-off-by: Sean Christopherson seanjc@google.com Reviewed-by: Liam Merwick liam.merwick@oracle.com Message-Id: 20220120010719.711476-2-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/svm/svm.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4464,8 +4464,13 @@ static bool svm_can_emulate_instruction( 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; @@ -4518,9 +4523,6 @@ static bool svm_can_emulate_instruction( 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); }