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

Michael Roth
2024-03-29T22:59:15Z

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)
--
2.25.1