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From:   Peter Gonda <pgonda@google.com>
Date:   Tue, 21 Jun 2022 11:50:59 -0600
Message-ID: <CAMkAt6qorwbAXaPaCaSm0SC9o2uQ9ZQzB6s1kBkvAv2D4tkUug@mail.gmail.com>
Subject: Re: [PATCH Part2 v6 02/49] iommu/amd: Introduce function to check
 SEV-SNP support
To:     "Kalra, Ashish" <Ashish.Kalra@amd.com>
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On Tue, Jun 21, 2022 at 11:45 AM Kalra, Ashish <Ashish.Kalra@amd.com> wrote:
>
> [AMD Official Use Only - General]
>
> Hello Peter,
>
> >> +bool iommu_sev_snp_supported(void)
> >> +{
> >> +       struct amd_iommu *iommu;
> >> +
> >> +       /*
> >> +        * The SEV-SNP support requires that IOMMU must be enabled, and is
> >> +        * not configured in the passthrough mode.
> >> +        */
> >> +       if (no_iommu || iommu_default_passthrough()) {
> >> +               pr_err("SEV-SNP: IOMMU is either disabled or
> >> + configured in passthrough mode.\n");
>
> > Like below could this say something like snp support is disabled because of iommu settings.
>
> Here we may need to be more precise with the error information indicating why SNP is not enabled.
> Please note that this patch may actually become part of the IOMMU + SNP patch series, where
> additional checks are done, for example, not enabling SNP if IOMMU v2 page tables are enabled,
> so precise error information will be useful here.

I agree we should be more precise. I just thought we should explicitly
state something like: "SEV-SNP: IOMMU is either disabled or configured
in passthrough mode, SNP cannot be supported".