linux-kernel - Re: [PATCH v10 48/50] KVM: SEV: Provide support for SNP_GUEST

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Date:   Mon, 16 Oct 2023 16:18:16 -0700
From:   Dionna Amalie Glaze <dionnaglaze@...gle.com>
To:     Michael Roth <michael.roth@....com>
Cc:     kvm@...r.kernel.org, linux-coco@...ts.linux.dev,
        linux-mm@...ck.org, linux-crypto@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        jroedel@...e.de, thomas.lendacky@....com, hpa@...or.com,
        ardb@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
        vkuznets@...hat.com, jmattson@...gle.com, luto@...nel.org,
        dave.hansen@...ux.intel.com, slp@...hat.com, pgonda@...gle.com,
        peterz@...radead.org, srinivas.pandruvada@...ux.intel.com,
        rientjes@...gle.com, dovmurik@...ux.ibm.com, tobin@....com,
        bp@...en8.de, vbabka@...e.cz, kirill@...temov.name,
        ak@...ux.intel.com, tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com,
        jarkko@...nel.org, ashish.kalra@....com, nikunj.dadhania@....com,
        pankaj.gupta@....com, liam.merwick@...cle.com,
        zhi.a.wang@...el.com, Brijesh Singh <brijesh.singh@....com>,
        Alexey Kardashevskiy <aik@....com>
Subject: Re: [PATCH v10 48/50] KVM: SEV: Provide support for SNP_GUEST_REQUEST
 NAE event

> +
> +       /*
> +        * If a VMM-specific certificate blob hasn't been provided, grab the
> +        * host-wide one.
> +        */
> +       snp_certs = sev_snp_certs_get(sev->snp_certs);
> +       if (!snp_certs)
> +               snp_certs = sev_snp_global_certs_get();
> +

This is where the generation I suggested adding would get checked. If
the instance certs' generation is not the global generation, then I
think we need a way to return to the VMM to make that right before
continuing to provide outdated certificates.
This might be an unreasonable request, but the fact that the certs and
reported_tcb can be set while a VM is running makes this an issue.

-- 
-Dionna Glaze, PhD (she/her)