Message-ID: <ba485a09-9c35-4115-decc-1b9c25519358@amd.com>
Date:   Fri, 10 Dec 2021 14:18:49 -0600
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Cc:     brijesh.singh@amd.com, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ard Biesheuvel <ardb@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Jim Mattson <jmattson@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        David Rientjes <rientjes@google.com>,
        Dov Murik <dovmurik@linux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@ibm.com>,
        Borislav Petkov <bp@alien8.de>,
        Michael Roth <michael.roth@amd.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Andi Kleen <ak@linux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        tony.luck@intel.com, marcorr@google.com,
        sathyanarayanan.kuppuswamy@linux.intel.com
Subject: Re: [PATCH v8 27/40] x86/boot: Add Confidential Computing type to
 setup_data
Content-Language: en-US
To:     Dave Hansen <dave.hansen@intel.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
        linux-coco@lists.linux.dev, linux-mm@kvack.org
References: <20211210154332.11526-1-brijesh.singh@amd.com>
 <20211210154332.11526-28-brijesh.singh@amd.com>
 <1fdaca61-884a-ac13-fb33-a47db198f050@intel.com>
From:   Brijesh Singh <brijesh.singh@amd.com>
In-Reply-To: <1fdaca61-884a-ac13-fb33-a47db198f050@intel.com>
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On 12/10/21 1:12 PM, Dave Hansen wrote:
> On 12/10/21 7:43 AM, Brijesh Singh wrote:
>> +/* AMD SEV Confidential computing blob structure */
>> +#define CC_BLOB_SEV_HDR_MAGIC	0x45444d41
>> +struct cc_blob_sev_info {
>> +	u32 magic;
>> +	u16 version;
>> +	u16 reserved;
>> +	u64 secrets_phys;
>> +	u32 secrets_len;
>> +	u64 cpuid_phys;
>> +	u32 cpuid_len;
>> +};
> This is an ABI structure rather than some purely kernel construct, right?


This is ABI between the guest BIOS and Guest OS. It is defined in the OVMF.

https://github.com/tianocore/edk2/blob/master/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h

SEV-SNP FW spec does not have it documented; it's up to the guest BIOS
on how it wants to communicate the Secrets and CPUID page location to
guest OS.


> I searched through all of the specs to which you linked in the cover
> letter.  I looked for "blob", "guid", the magic and part of the GUID
> itself trying to find where this is defined to see if the struct is correct.
>
> I couldn't find anything.
>
> Where is the spec for this blob?  How large is it?  Did you mean to
> leave a 4-byte hole after secrets_len and before cpuid_phys?

Yes, the length is never going to be > 4GB.