linux-kernel - Re: [PATCH Part1 v5 35/38] x86/sev: Register SNP guest request platform device

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Message-ID: <a42c782c-1de4-6c9f-4e97-cc4e1e48b358@amd.com>
Date:   Fri, 3 Sep 2021 07:08:06 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Dov Murik <dovmurik@...ux.ibm.com>, Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>, tony.luck@...el.com,
        marcorr@...gle.com, sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH Part1 v5 35/38] x86/sev: Register SNP guest request
 platform device


On 9/3/21 3:15 AM, Dov Murik wrote:
>> Unfortunately, the secrets page does not contain a magic header or uuid
>> which a guest can read to verify that the page is actually populated by
>> the PSP. 
> In the SNP FW ABI document section 8.14.2.5 there's a Table 61 titled
> Secrets Page Format, which states that the first field in that page is a
> u32 VERSION field which should equal 2h.
>
> While not as strict as GUID header, this can help detect early that the
> content of the SNP secrets page is invalid.

The description indicates that the field is a version number of the
secrets page format; it will get bumped every time the spec steals the
reserved bytes for something new. IMHO, we should not depend on the
version number.

thanks