[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <24770143-28e8-b4c5-5377-2125bdebe6b2@amd.com>
Date: Fri, 14 Mar 2025 14:59:36 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Kim Phillips <kim.phillips@....com>, kvm@...r.kernel.org,
linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Cc: Michael Roth <michael.roth@....com>, Ashish Kalra <ashish.kalra@....com>,
"Nikunj A . Dadhania" <nikunj@....com>,
Neeraj Upadhyay <Neeraj.Upadhyay@....com>, Naveen N Rao <naveen@...nel.org>,
Alexey Kardashevskiy <aik@....com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
<pbonzini@...hat.com>, Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v5 2/2] KVM: SEV: Configure "ALLOWED_SEV_FEATURES" VMCB
Field
On 3/10/25 15:16, 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@....com>
> Signed-off-by: Kishon Vijay Abraham I <kvijayab@....com>
> Reviewed-by: Pankaj Gupta <pankaj.gupta@....com>
> Signed-off-by: Kim Phillips <kim.phillips@....com>
Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
> ---
> arch/x86/include/asm/svm.h | 7 ++++++-
> arch/x86/kvm/svm/sev.c | 5 +++++
> arch/x86/kvm/svm/svm.c | 2 ++
> 3 files changed, 13 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..f9ec139901ef 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -4449,6 +4449,7 @@ void sev_vcpu_after_set_cpuid(struct vcpu_svm *svm)
>
> static void sev_es_init_vmcb(struct vcpu_svm *svm)
> {
> + struct kvm_sev_info *sev = to_kvm_sev_info(svm->vcpu.kvm);
> struct vmcb *vmcb = svm->vmcb01.ptr;
> struct kvm_vcpu *vcpu = &svm->vcpu;
>
> @@ -4464,6 +4465,10 @@ static void sev_es_init_vmcb(struct vcpu_svm *svm)
> if (svm->sev_es.vmsa && !svm->sev_es.snp_has_guest_vmsa)
> svm->vmcb->control.vmsa_pa = __pa(svm->sev_es.vmsa);
>
> + if (cpu_feature_enabled(X86_FEATURE_ALLOWED_SEV_FEATURES))
> + svm->vmcb->control.allowed_sev_features = sev->vmsa_features |
> + VMCB_ALLOWED_SEV_FEATURES_VALID;
> +
> /* Can't intercept CR register access, HV can't modify CR registers */
> svm_clr_intercept(svm, INTERCEPT_CR0_READ);
> svm_clr_intercept(svm, INTERCEPT_CR4_READ);
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 8abeab91d329..bff6e9c34586 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -3435,6 +3435,8 @@ static void dump_vmcb(struct kvm_vcpu *vcpu)
> pr_err("%-20s%016llx\n", "avic_logical_id:", control->avic_logical_id);
> pr_err("%-20s%016llx\n", "avic_physical_id:", control->avic_physical_id);
> pr_err("%-20s%016llx\n", "vmsa_pa:", control->vmsa_pa);
> + pr_err("%-20s%016llx\n", "allowed_sev_features:", control->allowed_sev_features);
> + pr_err("%-20s%016llx\n", "guest_sev_features:", control->guest_sev_features);
> pr_err("VMCB State Save Area:\n");
> pr_err("%-5s s: %04x a: %04x l: %08x b: %016llx\n",
> "es:",
Powered by blists - more mailing lists