linux-kernel - Re: [PATCH v17 1/3] x86/tdx: Add a wrapper to get TDREPORT from the TDX Module

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Message-ID: <8d5f8a74-f864-3cd9-dac2-7650d83a8b90@linux.intel.com>
Date:   Mon, 14 Nov 2022 16:33:52 -0800
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Shuah Khan <shuah@...nel.org>, Jonathan Corbet <corbet@....net>
Cc:     "H . Peter Anvin" <hpa@...or.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Kai Huang <kai.huang@...el.com>,
        Wander Lairson Costa <wander@...hat.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v17 1/3] x86/tdx: Add a wrapper to get TDREPORT from the
 TDX Module

Hi Dave,

On 11/11/22 10:35 AM, Dave Hansen wrote:
> This is *NOT* "a wrapper to get TDREPORT from the TDX Module", this is
> at best "a wrapper to get TDREPORT sub type 0 from the TDX Module".

In both the commit log and the comments, I can highlight the "subtype 0"
information. Will that work for you, or do you prefer that this wrapper
take the "subtype" option as argument and we pass 0 for the subtype value
from the TDX guest driver?

> 
> It also occurs to me that "sub type 0" could use an actual name.  Could
> we give it one, please?

Although the subtype option is mentioned in the TDX Module spec, it is not
currently used (it expects this value to be zero), and the spec also does
not explain why this option is required. According to TDX architects, this
option was primarily added to handle any future requirements that may arise
that require additional information to be added to the TDREPORT. However,
they do not currently have any valid use cases for it. So the current
version can only be described as "Type-0." Once a new use case for Subtype 1
is defined, we may be able to come up with a suitable name. Are you okay
with calling it "Type-0" for the time being?

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer