Re: [PATCH v6 9/9] KVM: selftests: Add a basic SEV-SNP smoke test

Sean Christopherson
2025-02-12T02:31:44Z

On Mon, Feb 03, 2025, Pratik R. Sampat wrote:
> @@ -217,5 +244,20 @@ int main(int argc, char *argv[])
> }
> }
>
> + if (kvm_cpu_has(X86_FEATURE_SEV_SNP)) {
> + uint64_t snp_policy = snp_default_policy();
> +
> + test_snp(snp_policy);
> + /* Test minimum firmware level */
> + test_snp(snp_policy | SNP_FW_VER_MAJOR(SNP_MIN_API_MAJOR) |
> + SNP_FW_VER_MINOR(SNP_MIN_API_MINOR));

Ah, this is where the firmware policy stuff is used. Refresh me, can userspace
request _any_ major/minor as the min, and expect failure if the version isn't
supported? If so, the test should iterate over the major/minor combinations that
are guaranteed to fail. And if userspace can query the supported minor/major,
the test should iterate over all the happy versions too.

Unless there's nothing interesting to test, I would move the major/minor stuff to
a separate patch.

> +
> + test_snp_shutdown(snp_policy);
> +
> + if (kvm_has_cap(KVM_CAP_XCRS) &&
> + (xgetbv(0) & kvm_cpu_supported_xcr0() & xf_mask) == xf_mask)
> + test_sync_vmsa_snp(snp_policy);

This is all copy+paste from SEV-ES tests, minus SEV_POLICY_NO_DBG. There's gotta
be a way to dedup this code.

Something like this?

static void needs_a_better_name(uint32_t type, uint64_t policy)
{
const u64 xf_mask = XFEATURE_MASK_X87_AVX;

test_sev(guest_sev_code, policy | SEV_POLICY_NO_DBG);
test_sev(guest_sev_code, policy);

if (type == KVM_X86_SEV_VM)
return;

test_sev_shutdown(policy);

if (kvm_has_cap(KVM_CAP_XCRS) &&
(xgetbv(0) & kvm_cpu_supported_xcr0() & xf_mask) == xf_mask) {
test_sync_vmsa(policy);
test_sync_vmsa(policy | SEV_POLICY_NO_DBG);
}
}

int main(int argc, char *argv[])
{
TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SEV));

needs_a_better_name(KVM_X86_SEV_VM, 0);

if (kvm_cpu_has(X86_FEATURE_SEV_ES))
needs_a_better_name(KVM_X86_SEV_ES_VM, 0);

if (kvm_cpu_has(X86_FEATURE_SEV_SNP))
needs_a_better_name(KVM_X86_SEV_SNP_VM, 0);

return 0;
}