From: Sean Christopherson Date: Thu, 27 Feb 2025 01:25:36 +0000 (-0800) Subject: KVM: SVM: Require AP's "requested" SEV_FEATURES to match KVM's view X-Git-Tag: v6.15-rc1~195^2~6^2~5 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=745ff82199b1d68585040a36f2f8c3a7987274cd;p=thirdparty%2Fkernel%2Flinux.git KVM: SVM: Require AP's "requested" SEV_FEATURES to match KVM's view When handling an "AP Create" event, return an error if the "requested" SEV features for the vCPU don't exactly match KVM's view of the VM-scoped features. There is no known use case for heterogeneous SEV features across vCPUs, and while KVM can't actually enforce an exact match since the value in RAX isn't guaranteed to match what the guest shoved into the VMSA, KVM can at least avoid knowingly letting the guest run in an unsupported state. E.g. if a VM is created with DebugSwap disabled, KVM will intercept #DBs and DRs for all vCPUs, even if an AP is "created" with DebugSwap enabled in its VMSA. Note, the GHCB spec only "requires" that "AP use the same interrupt injection mechanism as the BSP", but given the disaster that is DebugSwap and SEV_FEATURES in general, it's safe to say that AMD didn't consider all possible complications with mismatching features between the BSP and APs. Opportunistically fold the check into the relevant request flavors; the "request < AP_DESTROY" check is just a bizarre way of implementing the AP_CREATE_ON_INIT => AP_CREATE fallthrough. Fixes: e366f92ea99e ("KVM: SEV: Support SEV-SNP AP Creation NAE event") Reviewed-by: Tom Lendacky Reviewed-by: Pankaj Gupta Link: https://lore.kernel.org/r/20250227012541.3234589-6-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h index 12a9dde1e8425..9b7fa99ae9513 100644 --- a/arch/x86/include/asm/svm.h +++ b/arch/x86/include/asm/svm.h @@ -291,10 +291,6 @@ static_assert((X2AVIC_MAX_PHYSICAL_ID & AVIC_PHYSICAL_MAX_INDEX_MASK) == X2AVIC_ #define SVM_SEV_FEAT_ALTERNATE_INJECTION BIT(4) #define SVM_SEV_FEAT_DEBUG_SWAP BIT(5) -#define SVM_SEV_FEAT_INT_INJ_MODES \ - (SVM_SEV_FEAT_RESTRICTED_INJECTION | \ - SVM_SEV_FEAT_ALTERNATE_INJECTION) - struct vmcb_seg { u16 selector; u16 attrib; diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 2b76957209e68..8bc81a5a81598 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -3938,6 +3938,7 @@ unlock: static int sev_snp_ap_creation(struct vcpu_svm *svm) { + struct kvm_sev_info *sev = to_kvm_sev_info(svm->vcpu.kvm); struct kvm_vcpu *vcpu = &svm->vcpu; struct kvm_vcpu *target_vcpu; struct vcpu_svm *target_svm; @@ -3969,26 +3970,18 @@ static int sev_snp_ap_creation(struct vcpu_svm *svm) mutex_lock(&target_svm->sev_es.snp_vmsa_mutex); - /* Interrupt injection mode shouldn't change for AP creation */ - if (request < SVM_VMGEXIT_AP_DESTROY) { - u64 sev_features; - - sev_features = vcpu->arch.regs[VCPU_REGS_RAX]; - sev_features ^= to_kvm_sev_info(svm->vcpu.kvm)->vmsa_features; - - if (sev_features & SVM_SEV_FEAT_INT_INJ_MODES) { - vcpu_unimpl(vcpu, "vmgexit: invalid AP injection mode [%#lx] from guest\n", - vcpu->arch.regs[VCPU_REGS_RAX]); - ret = -EINVAL; - goto out; - } - } - switch (request) { case SVM_VMGEXIT_AP_CREATE_ON_INIT: kick = false; fallthrough; case SVM_VMGEXIT_AP_CREATE: + if (vcpu->arch.regs[VCPU_REGS_RAX] != sev->vmsa_features) { + vcpu_unimpl(vcpu, "vmgexit: mismatched AP sev_features [%#lx] != [%#llx] from guest\n", + vcpu->arch.regs[VCPU_REGS_RAX], sev->vmsa_features); + ret = -EINVAL; + goto out; + } + if (!page_address_valid(vcpu, svm->vmcb->control.exit_info_2)) { vcpu_unimpl(vcpu, "vmgexit: invalid AP VMSA address [%#llx] from guest\n", svm->vmcb->control.exit_info_2);