Re: [PATCH 2/4] selftests/kvm: check that SEV-ES VMs are allowed in SEV-SNP mode

[Sean Christopherson <seanjc@google.com>]

On Mon, Feb 23, 2026, Tycho Andersen wrote:
> diff --git a/tools/testing/selftests/kvm/x86/sev_smoke_test.c b/tools/testing/selftests/kvm/x86/sev_smoke_test.c
> index 86ad1c7d068f..c7fda9fc324b 100644
> --- a/tools/testing/selftests/kvm/x86/sev_smoke_test.c
> +++ b/tools/testing/selftests/kvm/x86/sev_smoke_test.c
> @@ -213,13 +213,48 @@ static void test_sev_smoke(void *guest, uint32_t type, uint64_t policy)
>  	}
>  }
>  
> +static bool sev_es_allowed(void)
> +{
> +	struct kvm_sev_launch_start launch_start = {
> +		.policy = SEV_POLICY_ES,
> +	};
> +	struct kvm_vcpu *vcpu;
> +	struct kvm_vm *vm;
> +	int firmware_error, ret;
> +	bool supported = true;
> +
> +	if (!kvm_cpu_has(X86_FEATURE_SEV_ES))
> +		return false;
> +
> +	if (!kvm_cpu_has(X86_FEATURE_SEV_SNP))
> +		return true;
> +
> +	/*
> +	 * In some cases when SEV-SNP is enabled, firmware disallows starting
> +	 * an SEV-ES VM. When SEV-SNP is enabled try to launch an SEV-ES, and
> +	 * check the underlying firmware error for this case.
> +	 */
> +	vm = vm_sev_create_with_one_vcpu(KVM_X86_SEV_ES_VM, guest_sev_es_code,
> +					 &vcpu);

If there's a legimate reason why an SEV-ES VM can't be created, then that needs
to be explicitly enumerated in some way by the kernel.  E.g. is this due to lack
of ASIDs due to CipherTextHiding or something?  Throwing a noodle to see if it
sticks is not an option.

> +
> +	ret = __vm_sev_ioctl(vm, KVM_SEV_LAUNCH_START, &launch_start,
> +			     &firmware_error);
> +	if (ret == -1 && firmware_error == SEV_RET_UNSUPPORTED) {
> +		pr_info("SEV-ES not supported with SNP\n");
> +		supported = false;
> +	}
> +
> +	kvm_vm_free(vm);
> +	return supported;
> +}
> +
>  int main(int argc, char *argv[])
>  {
>  	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SEV));
>  
>  	test_sev_smoke(guest_sev_code, KVM_X86_SEV_VM, 0);
>  
> -	if (kvm_cpu_has(X86_FEATURE_SEV_ES))
> +	if (sev_es_allowed())
>  		test_sev_smoke(guest_sev_es_code, KVM_X86_SEV_ES_VM, SEV_POLICY_ES);
>  
>  	if (kvm_cpu_has(X86_FEATURE_SEV_SNP))
> -- 
> 2.53.0
>