KVM: selftests: SEV-SNP test for KVM_SEV_INIT2

Add the X86_FEATURE_SEV_SNP CPU feature to the architectural definition
for the SEV-SNP VM type to exercise the KVM_SEV_INIT2 call. Ensure that
the SNP test is skipped in scenarios where CPUID supports it but KVM
does not, preventing reporting of failure in such cases.

Reviewed-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Pratik R. Sampat <prsampat@amd.com>
Link: https://lore.kernel.org/r/20250305230000.231025-3-prsampat@amd.com
[sean: use the same pattern as SEV and SEV-ES]
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: pratiksampat

tools/testing/selftests/kvm/include/x86/processor.h

@@ -203,6 +203,7 @@ struct kvm_x86_cpu_feature {
 #define X86_FEATURE_IDLE_HLT		KVM_X86_CPU_FEATURE(0x8000000A, 0, EDX, 30)
 #define X86_FEATURE_SEV			KVM_X86_CPU_FEATURE(0x8000001F, 0, EAX, 1)
 #define X86_FEATURE_SEV_ES		KVM_X86_CPU_FEATURE(0x8000001F, 0, EAX, 3)
+#define X86_FEATURE_SEV_SNP		KVM_X86_CPU_FEATURE(0x8000001F, 0, EAX, 4)
 #define	X86_FEATURE_PERFMON_V2		KVM_X86_CPU_FEATURE(0x80000022, 0, EAX, 0)
 #define	X86_FEATURE_LBR_PMC_FREEZE	KVM_X86_CPU_FEATURE(0x80000022, 0, EAX, 2)
 

tools/testing/selftests/kvm/x86/sev_init2_tests.c

@@ -28,6 +28,7 @@
 int kvm_fd;
 u64 supported_vmsa_features;
 bool have_sev_es;
+bool have_snp;
 
 static int __sev_ioctl(int vm_fd, int cmd_id, void *data)
 {
@@ -83,6 +84,9 @@ void test_vm_types(void)
 	if (have_sev_es)
 		test_init2(KVM_X86_SEV_ES_VM, &(struct kvm_sev_init){});
 
+	if (have_snp)
+		test_init2(KVM_X86_SNP_VM, &(struct kvm_sev_init){});
+
 	test_init2_invalid(0, &(struct kvm_sev_init){},
 			   "VM type is KVM_X86_DEFAULT_VM");
 	if (kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM))
@@ -138,15 +142,24 @@ int main(int argc, char *argv[])
 		    "sev-es: KVM_CAP_VM_TYPES (%x) does not match cpuid (checking %x)",
 		    kvm_check_cap(KVM_CAP_VM_TYPES), 1 << KVM_X86_SEV_ES_VM);
 
+	have_snp = kvm_cpu_has(X86_FEATURE_SEV_SNP);
+	TEST_ASSERT(have_snp == !!(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SNP_VM)),
+		    "sev-snp: KVM_CAP_VM_TYPES (%x) indicates SNP support (bit %d), but CPUID does not",
+		    kvm_check_cap(KVM_CAP_VM_TYPES), KVM_X86_SNP_VM);
+
 	test_vm_types();
 
 	test_flags(KVM_X86_SEV_VM);
 	if (have_sev_es)
 		test_flags(KVM_X86_SEV_ES_VM);
+	if (have_snp)
+		test_flags(KVM_X86_SNP_VM);
 
 	test_features(KVM_X86_SEV_VM, 0);
 	if (have_sev_es)
 		test_features(KVM_X86_SEV_ES_VM, supported_vmsa_features);
+	if (have_snp)
+		test_features(KVM_X86_SNP_VM, supported_vmsa_features);
 
 	return 0;
 }