6.12-stable review patch. If anyone has any objections, please let me know.
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From: Sean Christopherson seanjc@google.com
commit d26638bfcdfc5c8c4e085dc3f5976a0443abab3c upstream.
If KVM rejects an AP Creation event, leave the target vCPU state as-is. Nothing in the GHCB suggests the hypervisor is *allowed* to muck with vCPU state on failure, let alone required to do so. Furthermore, kicking only in the !ON_INIT case leads to divergent behavior, and even the "kick" case is non-deterministic.
E.g. if an ON_INIT request fails, the guest can successfully retry if the fixed AP Creation request is made prior to sending INIT. And if a !ON_INIT fails, the guest can successfully retry if the fixed AP Creation request is handled before the target vCPU processes KVM's KVM_REQ_UPDATE_PROTECTED_GUEST_STATE.
Fixes: e366f92ea99e ("KVM: SEV: Support SEV-SNP AP Creation NAE event") Cc: stable@vger.kernel.org Reviewed-by: Tom Lendacky thomas.lendacky@amd.com Reviewed-by: Pankaj Gupta pankaj.gupta@amd.com Link: https://lore.kernel.org/r/20250227012541.3234589-5-seanjc@google.com Signed-off-by: Sean Christopherson seanjc@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/svm/sev.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)
--- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -3957,16 +3957,12 @@ static int sev_snp_ap_creation(struct vc
/* * The target vCPU is valid, so the vCPU will be kicked unless the - * request is for CREATE_ON_INIT. For any errors at this stage, the - * kick will place the vCPU in an non-runnable state. + * request is for CREATE_ON_INIT. */ kick = true;
mutex_lock(&target_svm->sev_es.snp_vmsa_mutex);
- target_svm->sev_es.snp_vmsa_gpa = INVALID_PAGE; - target_svm->sev_es.snp_ap_waiting_for_reset = true; - /* Interrupt injection mode shouldn't change for AP creation */ if (request < SVM_VMGEXIT_AP_DESTROY) { u64 sev_features; @@ -4012,20 +4008,23 @@ static int sev_snp_ap_creation(struct vc target_svm->sev_es.snp_vmsa_gpa = svm->vmcb->control.exit_info_2; break; case SVM_VMGEXIT_AP_DESTROY: + target_svm->sev_es.snp_vmsa_gpa = INVALID_PAGE; break; default: vcpu_unimpl(vcpu, "vmgexit: invalid AP creation request [%#x] from guest\n", request); ret = -EINVAL; - break; + goto out; }
-out: + target_svm->sev_es.snp_ap_waiting_for_reset = true; + if (kick) { kvm_make_request(KVM_REQ_UPDATE_PROTECTED_GUEST_STATE, target_vcpu); kvm_vcpu_kick(target_vcpu); }
+out: mutex_unlock(&target_svm->sev_es.snp_vmsa_mutex);
return ret;