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Date:   Sun, 25 Jun 2023 20:07:32 -0700
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Subject: Re: [PATCH v3 0/3] TDX Guest Quote generation support
To:     Dan Williams <dan.j.williams@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        Shuah Khan <shuah@kernel.org>, Jonathan Corbet <corbet@lwn.net>
Cc:     "H . Peter Anvin" <hpa@zytor.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Wander Lairson Costa <wander@redhat.com>,
        Erdem Aktas <erdemaktas@google.com>,
        Dionna Amalie Glaze <dionnaglaze@google.com>,
        Chong Cai <chongc@google.com>, Qinkun Bao <qinkun@apache.org>,
        Guorui Yu <GuoRui.Yu@linux.alibaba.com>,
        Du Fan <fan.du@intel.com>, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org
References: <cover.1684048511.git.sathyanarayanan.kuppuswamy@linux.intel.com>
 <64966b842becf_142af8294a5@dwillia2-xfh.jf.intel.com.notmuch>
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From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@linux.intel.com>
In-Reply-To: <64966b842becf_142af8294a5@dwillia2-xfh.jf.intel.com.notmuch>
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On 6/23/23 9:05 PM, Dan Williams wrote:
> Kuppuswamy Sathyanarayanan wrote:
>> Hi All,
>>
>> In TDX guest, the attestation process is used to verify the TDX guest
>> trustworthiness to other entities before provisioning secrets to the
>> guest.
>>
>> The TDX guest attestation process consists of two steps:
>>
>> 1. TDREPORT generation
>> 2. Quote generation.
>>
>> The First step (TDREPORT generation) involves getting the TDX guest
>> measurement data in the format of TDREPORT which is further used to
>> validate the authenticity of the TDX guest. The second step involves
>> sending the TDREPORT to a Quoting Enclave (QE) server to generate a
>> remotely verifiable Quote. TDREPORT by design can only be verified on
>> the local platform. To support remote verification of the TDREPORT,
>> TDX leverages Intel SGX Quoting Enclave to verify the TDREPORT
>> locally and convert it to a remotely verifiable Quote. Although
>> attestation software can use communication methods like TCP/IP or
>> vsock to send the TDREPORT to QE, not all platforms support these
>> communication models. So TDX GHCI specification [1] defines a method
>> for Quote generation via hypercalls. Please check the discussion from
>> Google [2] and Alibaba [3] which clarifies the need for hypercall based
>> Quote generation support. This patch set adds this support.
>>
>> Support for TDREPORT generation already exists in the TDX guest driver. 
>> This patchset extends the same driver to add the Quote generation
>> support.
> 
> I missed that the TDREPORT ioctl() and this character device are already
> upstream. The TDREPORT ioctl() if it is only needed for quote generation
> seems a waste because it just retrieves a blob that needs to be turned
> around and injected back into the kernel to generate a quote.

Although the end goal is to generate the quote, the method the user chooses to
achieve it may differ for a variety of reasons. In this case, we're trying to
support the use case where the user will use methods like TCP/IP or vsock to
generate the Quote. They can use the GET_REPORT IOCTL to get the TDREPORT and
send it to the quoting enclave via the above-mentioned methods.  TDVMCALL-based
quote generation is intended for users who, for a variety of security reasons, do
not wish to use the methods described above.


-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer