Re: [PATCH v12 09/29] KVM: SEV: Add initial SEV-SNP support

Paolo Bonzini
2024-03-30T19:58:50Z

On 3/29/24 23:58, Michael Roth wrote:
> SEV-SNP builds upon existing SEV and SEV-ES functionality while adding
> new hardware-based security protection. SEV-SNP adds strong memory
> encryption and integrity protection to help prevent malicious
> hypervisor-based attacks such as data replay, memory re-mapping, and
> more, to create an isolated execution environment.
>
> Define a new KVM_X86_SNP_VM type which makes use of these capabilities
> and extend the KVM_SEV_INIT2 ioctl to support it. Also add a basic
> helper to check whether SNP is enabled.
>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> [mdr: commit fixups, use similar ASID reporting as with SEV/SEV-ES]
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> ---
> arch/x86/include/asm/svm.h | 3 ++-
> arch/x86/include/uapi/asm/kvm.h | 1 +
> arch/x86/kvm/svm/sev.c | 21 ++++++++++++++++++++-
> arch/x86/kvm/svm/svm.c | 3 ++-
> arch/x86/kvm/svm/svm.h | 12 ++++++++++++
> arch/x86/kvm/x86.c | 2 +-
> 6 files changed, 38 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
> index 728c98175b9c..544a43c1cf11 100644
> --- a/arch/x86/include/asm/svm.h
> +++ b/arch/x86/include/asm/svm.h
> @@ -285,7 +285,8 @@ static_assert((X2AVIC_MAX_PHYSICAL_ID & AVIC_PHYSICAL_MAX_INDEX_MASK) == X2AVIC_
>
> #define AVIC_HPA_MASK ~((0xFFFULL << 52) | 0xFFF)
>
> -#define SVM_SEV_FEAT_DEBUG_SWAP BIT(5)
> +#define SVM_SEV_FEAT_SNP_ACTIVE BIT(0)
> +#define SVM_SEV_FEAT_DEBUG_SWAP BIT(5)
>
> struct vmcb_seg {
> u16 selector;
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 51b13080ed4b..725b75cfe9ff 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -868,5 +868,6 @@ struct kvm_hyperv_eventfd {
> #define KVM_X86_SW_PROTECTED_VM 1
> #define KVM_X86_SEV_VM 2
> #define KVM_X86_SEV_ES_VM 3
> +#define KVM_X86_SNP_VM 4
>
> #endif /* _ASM_X86_KVM_H */
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 1e65f5634ad3..3d9771163562 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -46,6 +46,9 @@ module_param_named(sev, sev_enabled, bool, 0444);
> static bool sev_es_enabled = true;
> module_param_named(sev_es, sev_es_enabled, bool, 0444);
>
> +/* enable/disable SEV-SNP support */
> +static bool sev_snp_enabled;
> +
> /* enable/disable SEV-ES DebugSwap support */
> static bool sev_es_debug_swap_enabled = true;
> module_param_named(debug_swap, sev_es_debug_swap_enabled, bool, 0444);
> @@ -275,6 +278,9 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp,
> sev->es_active = es_active;
> sev->vmsa_features = data->vmsa_features;
>
> + if (vm_type == KVM_X86_SNP_VM)
> + sev->vmsa_features |= SVM_SEV_FEAT_SNP_ACTIVE;
> +
> ret = sev_asid_new(sev);
> if (ret)
> goto e_no_asid;
> @@ -326,7 +332,8 @@ static int sev_guest_init2(struct kvm *kvm, struct kvm_sev_cmd *argp)
> return -EINVAL;
>
> if (kvm->arch.vm_type != KVM_X86_SEV_VM &&
> - kvm->arch.vm_type != KVM_X86_SEV_ES_VM)
> + kvm->arch.vm_type != KVM_X86_SEV_ES_VM &&
> + kvm->arch.vm_type != KVM_X86_SNP_VM)
> return -EINVAL;
>
> if (copy_from_user(&data, u64_to_user_ptr(argp->data), sizeof(data)))
> @@ -2297,11 +2304,16 @@ void __init sev_set_cpu_caps(void)
> kvm_cpu_cap_set(X86_FEATURE_SEV_ES);
> kvm_caps.supported_vm_types |= BIT(KVM_X86_SEV_ES_VM);
> }
> + if (sev_snp_enabled) {
> + kvm_cpu_cap_set(X86_FEATURE_SEV_SNP);
> + kvm_caps.supported_vm_types |= BIT(KVM_X86_SNP_VM);
> + }
> }
>
> void __init sev_hardware_setup(void)
> {
> unsigned int eax, ebx, ecx, edx, sev_asid_count, sev_es_asid_count;
> + bool sev_snp_supported = false;
> bool sev_es_supported = false;
> bool sev_supported = false;
>
> @@ -2382,6 +2394,7 @@ void __init sev_hardware_setup(void)
> sev_es_asid_count = min_sev_asid - 1;
> WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count));
> sev_es_supported = true;
> + sev_snp_supported = sev_snp_enabled && cc_platform_has(CC_ATTR_HOST_SEV_SNP);
>
> out:
> if (boot_cpu_has(X86_FEATURE_SEV))
> @@ -2394,9 +2407,15 @@ void __init sev_hardware_setup(void)
> pr_info("SEV-ES %s (ASIDs %u - %u)\n",
> sev_es_supported ? "enabled" : "disabled",
> min_sev_asid > 1 ? 1 : 0, min_sev_asid - 1);
> + if (boot_cpu_has(X86_FEATURE_SEV_SNP))
> + pr_info("SEV-SNP %s (ASIDs %u - %u)\n",
> + sev_snp_supported ? "enabled" : "disabled",
> + min_sev_asid > 1 ? 1 : 0, min_sev_asid - 1);
>
> sev_enabled = sev_supported;
> sev_es_enabled = sev_es_supported;
> + sev_snp_enabled = sev_snp_supported;
> +
> if (!sev_es_enabled || !cpu_feature_enabled(X86_FEATURE_DEBUG_SWAP) ||
> !cpu_feature_enabled(X86_FEATURE_NO_NESTED_DATA_BP))
> sev_es_debug_swap_enabled = false;
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 0f3b59da0d4a..2c162f6a1d78 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4890,7 +4890,8 @@ static int svm_vm_init(struct kvm *kvm)
>
> if (type != KVM_X86_DEFAULT_VM &&
> type != KVM_X86_SW_PROTECTED_VM) {
> - kvm->arch.has_protected_state = (type == KVM_X86_SEV_ES_VM);
> + kvm->arch.has_protected_state =
> + (type == KVM_X86_SEV_ES_VM || type == KVM_X86_SNP_VM);
> to_kvm_sev_info(kvm)->need_init = true;
> }
>
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index 157eb3f65269..4a01a81dd9b9 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -348,6 +348,18 @@ static __always_inline bool sev_es_guest(struct kvm *kvm)
> #endif
> }
>
> +static __always_inline bool sev_snp_guest(struct kvm *kvm)
> +{
> +#ifdef CONFIG_KVM_AMD_SEV
> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> +
> + return (sev->vmsa_features & SVM_SEV_FEAT_SNP_ACTIVE) &&
> + !WARN_ON_ONCE(!sev_es_guest(kvm));
> +#else
> + return false;
> +#endif
> +}
> +
> static inline void vmcb_mark_all_dirty(struct vmcb *vmcb)
> {
> vmcb->control.clean = 0;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 64eda7949f09..f85735b6235d 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -12603,7 +12603,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>
> kvm->arch.vm_type = type;
> kvm->arch.has_private_mem =
> - (type == KVM_X86_SW_PROTECTED_VM);
> + (type == KVM_X86_SW_PROTECTED_VM || type == KVM_X86_SNP_VM);
>
> ret = kvm_page_track_init(kvm);
> if (ret)

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Paolo