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Date:   Tue, 19 Apr 2022 07:13:11 -0700
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To:     Kai Huang <kai.huang@intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.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,
        Hans de Goede <hdegoede@redhat.com>,
        Mark Gross <mgross@linux.intel.com>
Cc:     "H . Peter Anvin" <hpa@zytor.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Andi Kleen <ak@linux.intel.com>, linux-kernel@vger.kernel.org,
        platform-driver-x86@vger.kernel.org
References: <20220415220109.282834-1-sathyanarayanan.kuppuswamy@linux.intel.com>
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From:   Dave Hansen <dave.hansen@intel.com>
Subject: Re: [PATCH v3 4/4] platform/x86: intel_tdx_attest: Add TDX Guest
 attestation interface driver
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On 4/19/22 00:47, Kai Huang wrote:
>>From security's perspective, attestation is an essential part of TDX.  That
> being said, w/o attestation support in TD guest, I guess nobody will seriously
> use TD guest.

Are you saying you can't think of a single threat model where there's a
benefit to running a TDX guest without attestation?  Will TDX only be
used in environments where secrets are provisioned to guests on the
basis of attestation?

>>From this perspective, I am not sure what's the value of having a dedicated
> INTEL_TDX_ATTESTATION Kconfig.  The attestation support code should be turned on
> unconditionally when CONFIG_INTEL_TDX_GUEST is on.  The code can also be just
> under arch/x86/coco/tdx/ I guess?

How much code are we talking about?  What's the difference in the size
of the binaries with this compiled in?