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    SubjectRe: [PATCH v6 08/42] x86/sev-es: initialize sev_status/features within #VC handler
    On Mon, Oct 25, 2021 at 11:35:18AM -0500, Michael Roth wrote:
    > As counter-intuitive as it sounds, it actually doesn't buy us if the CPUID
    > table is part of the PSP attestation report, since:

    Thanks for taking the time to explain in detail - I think I know now
    what's going on, and David explained some additional stuff to me
    yesterday.

    So, to cut to the chase:

    - yeah, ok, I guess guest owner attestation is what should happen.

    - as to the boot detection, I think you should do in sme_enable(), in
    pseudo:

    bool snp_guest_detected;

    if (CPUID page address) {
    read SEV_STATUS;

    snp_guest_detected = SEV_STATUS & MSR_AMD64_SEV_SNP_ENABLED;
    }

    /* old SME/SEV detection path */
    read 0x8000_001F_EAX and look at bits SME and SEV, yadda yadda.

    if (snp_guest_detected && (!SME || !SEV))
    /*
    * HV is lying to me, do something there, dunno what. I guess we can
    * continue booting unencrypted so that the guest owner knows that
    * detection has failed and maybe the HV didn't want us to force SNP.
    * This way, attestation will fail and the user will know why.
    * Or something like that.
    */


    /* normal feature detection continues. */

    How does that sound?

    --
    Regards/Gruss,
    Boris.

    https://people.kernel.org/tglx/notes-about-netiquette

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