linux-kernel - Re: [PATCH v3 5/5] virt: sevguest: Add TSM_REPORTS support for SNP_{GET, GET_EXT}

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Date:   Mon, 4 Sep 2023 02:14:55 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "Williams, Dan J" <dan.j.williams@...el.com>,
        "linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>,
        "jpiotrowski@...ux.microsoft.com" <jpiotrowski@...ux.microsoft.com>
CC:     "bp@...en8.de" <bp@...en8.de>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "thomas.lendacky@....com" <thomas.lendacky@....com>,
        "dionnaglaze@...gle.com" <dionnaglaze@...gle.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "brijesh.singh@....com" <brijesh.singh@....com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>
Subject: Re: [PATCH v3 5/5] virt: sevguest: Add TSM_REPORTS support for
 SNP_{GET, GET_EXT}_REPORT

On Fri, 2023-09-01 at 09:38 -0700, Dan Williams wrote:
> > The extended guest request is another topic, since userspace has to be aware of
> > where the kernel choses to put the extended data, and fixup all the offsets in the
> > table (section 4.1.8.1 in [2]). It would be better to return this data through a
> > separate file.
> 
> I notice that the TDX report also includes a certificate blob, so if
> that is a common concept then yes, it makes sense to have a separate
> file for that.

+ Sathy and Isaku.

It is a common concept from the perspective of "concept", because we need
certificates to verify the attestation blob anyway.  But in implementation,
unlike to SEV, TDX doesn't have a command to return certificates separately or
independently [1] -- they are embed to the Quote itself, or theoretically can be
fetched from Intel.  

More, for TDX (SGX based attestation) certificates blob itself isn't mandatory
to be part of the Quote.  Instead, TDX Quote can choose to include some more
basic platform identification which can in turn be used to get those
certificates from Intel's provisioning certificate service [2].

[1] I am not sure whether we can add one or already have one in the latest TDX
development.  Maybe Sathy or Isaku can help to confirm.

[2]: Table 9: QE Certification Data
https://download.01.org/intel-sgx/dcap-1.0.1/docs/Intel_SGX_ECDSA_QuoteGenReference_DCAP_API_Linux_1.0.1.pdf