On 3/5/25 18:38, Kim Phillips wrote: > AMD EPYC 5th generation processors have introduced a feature that allows > the hypervisor to control the SEV_FEATURES that are set for, or by, a > guest [1]. ALLOWED_SEV_FEATURES can be used by the hypervisor to enforce > that SEV-ES and SEV-SNP guests cannot enable features that the > hypervisor does not want to be enabled. > > Always enable ALLOWED_SEV_FEATURES. A VMRUN will fail if any > non-reserved bits are 1 in SEV_FEATURES but are 0 in > ALLOWED_SEV_FEATURES. > > Some SEV_FEATURES - currently PmcVirtualization and SecureAvic > (see Appendix B, Table B-4) - require an opt-in via ALLOWED_SEV_FEATURES, > i.e. are off-by-default, whereas all other features are effectively > on-by-default, but still honor ALLOWED_SEV_FEATURES. > > [1] Section 15.36.20 "Allowed SEV Features", AMD64 Architecture > Programmer's Manual, Pub. 24593 Rev. 3.42 - March 2024: > https://bugzilla.kernel.org/attachment.cgi?id=306250 > > Co-developed-by: Kishon Vijay Abraham I <kvijayab@xxxxxxx> > Signed-off-by: Kishon Vijay Abraham I <kvijayab@xxxxxxx> > Signed-off-by: Kim Phillips <kim.phillips@xxxxxxx> > --- > arch/x86/include/asm/svm.h | 7 ++++++- > arch/x86/kvm/svm/sev.c | 13 +++++++++++++ > 2 files changed, 19 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h > index 9b7fa99ae951..b382fd251e5b 100644 > --- a/arch/x86/include/asm/svm.h > +++ b/arch/x86/include/asm/svm.h > @@ -159,7 +159,10 @@ struct __attribute__ ((__packed__)) vmcb_control_area { > u64 avic_physical_id; /* Offset 0xf8 */ > u8 reserved_7[8]; > u64 vmsa_pa; /* Used for an SEV-ES guest */ > - u8 reserved_8[720]; > + u8 reserved_8[40]; > + u64 allowed_sev_features; /* Offset 0x138 */ > + u64 guest_sev_features; /* Offset 0x140 */ > + u8 reserved_9[664]; > /* > * Offset 0x3e0, 32 bytes reserved > * for use by hypervisor/software. > @@ -291,6 +294,8 @@ 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 VMCB_ALLOWED_SEV_FEATURES_VALID BIT_ULL(63) > + > struct vmcb_seg { > u16 selector; > u16 attrib; > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 0bc708ee2788..7f6cb950edcf 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -793,6 +793,14 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp) > return ret; > } > > +static u64 allowed_sev_features(struct kvm_sev_info *sev) > +{ > + if (cpu_feature_enabled(X86_FEATURE_ALLOWED_SEV_FEATURES)) > + return sev->vmsa_features | VMCB_ALLOWED_SEV_FEATURES_VALID; > + > + return 0; > +} > + > static int sev_es_sync_vmsa(struct vcpu_svm *svm) > { > struct kvm_vcpu *vcpu = &svm->vcpu; > @@ -891,6 +899,7 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm) > static int __sev_launch_update_vmsa(struct kvm *kvm, struct kvm_vcpu *vcpu, > int *error) > { > + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; > struct sev_data_launch_update_vmsa vmsa; > struct vcpu_svm *svm = to_svm(vcpu); > int ret; > @@ -900,6 +909,8 @@ static int __sev_launch_update_vmsa(struct kvm *kvm, struct kvm_vcpu *vcpu, > return -EINVAL; > } > > + svm->vmcb->control.allowed_sev_features = allowed_sev_features(sev); I think you can move this to sev_es_init_vmcb() and have it just in that one place instead of each launch update routine. Thanks, Tom > + > /* Perform some pre-encryption checks against the VMSA */ > ret = sev_es_sync_vmsa(svm); > if (ret) > @@ -2426,6 +2437,8 @@ static int snp_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp) > struct vcpu_svm *svm = to_svm(vcpu); > u64 pfn = __pa(svm->sev_es.vmsa) >> PAGE_SHIFT; > > + svm->vmcb->control.allowed_sev_features = allowed_sev_features(sev); > + > ret = sev_es_sync_vmsa(svm); > if (ret) > return ret;
