linux-kernel - Re: [RFC 1/5] selftests: KVM: Add a basic SNP smoke test

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Message-ID: <CAMkAt6oc5YC8oLpvFDeCOrEH6Hm88M_U_eMBPXpQWvcqjL7nzg@mail.gmail.com>
Date: Thu, 11 Jul 2024 09:16:05 -0600
From: Peter Gonda <pgonda@...gle.com>
To: "Pratik R. Sampat" <pratikrajesh.sampat@....com>
Cc: kvm@...r.kernel.org, shuah@...nel.org, thomas.lendacky@....com, 
	michael.roth@....com, seanjc@...gle.com, pbonzini@...hat.com, 
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 1/5] selftests: KVM: Add a basic SNP smoke test

On Wed, Jul 10, 2024 at 4:06 PM Pratik R. Sampat
<pratikrajesh.sampat@....com> wrote:
>
> Extend sev_smoke_test to also run a minimal SEV-SNP smoke test that
> initializes and sets up private memory regions required to run a simple
> SEV-SNP guest.
>
> Similar to it's SEV-ES smoke test counterpart, this also does not support
> GHCB and ucall yet and uses the GHCB MSR protocol to trigger an exit of
> the type KVM_EXIT_SYSTEM_EVENT.
>
> Also, decouple policy and type and require functions to provide both
> such that there is no assumption regarding the type using policy.
>
> Signed-off-by: Pratik R. Sampat <pratikrajesh.sampat@....com>

Tested-by: Peter Gonda <pgonda@...gle.com>

>
> -       test_sev(guest_sev_code, SEV_POLICY_NO_DBG);
> -       test_sev(guest_sev_code, 0);
> +       test_sev(guest_sev_code, KVM_X86_SEV_VM, SEV_POLICY_NO_DBG);
> +       test_sev(guest_sev_code, KVM_X86_SEV_VM, 0);
>
>         if (kvm_cpu_has(X86_FEATURE_SEV_ES)) {
> -               test_sev(guest_sev_es_code, SEV_POLICY_ES | SEV_POLICY_NO_DBG);
> -               test_sev(guest_sev_es_code, SEV_POLICY_ES);
> +               test_sev(guest_sev_es_code, KVM_X86_SEV_ES_VM, SEV_POLICY_ES | SEV_POLICY_NO_DBG);
> +               test_sev(guest_sev_es_code, KVM_X86_SEV_ES_VM, SEV_POLICY_ES);
> +
> +               if (kvm_has_cap(KVM_CAP_XCRS) &&
> +                   (xgetbv(0) & XFEATURE_MASK_X87_AVX) == XFEATURE_MASK_X87_AVX) {
> +                       test_sync_vmsa(KVM_X86_SEV_ES_VM, SEV_POLICY_ES);
> +                       test_sync_vmsa(KVM_X86_SEV_ES_VM, SEV_POLICY_ES | SEV_POLICY_NO_DBG);
> +               }
> +       }
> +
> +       if (kvm_cpu_has(X86_FEATURE_SNP) && is_kvm_snp_supported()) {
> +               test_sev(guest_snp_code, KVM_X86_SNP_VM, SNP_POLICY_SMT | SNP_POLICY_RSVD_MBO);

I'd guess most systems have SMT enabled, but is there a way we can
check and toggle the SNP_POLICY_SMT policy bit programmatically?

Also should we have a base SNP policy so we don't have to read
`SNP_POLICY_SMT | SNP_POLICY_RSVD_MBO` every time? Not sure I think
selftests prefer more verbosity.