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Date: Tue, 13 Feb 2024 16:53:06 -0800
From: Dan Williams <dan.j.williams@intel.com>
To: Theodore Ts'o <tytso@mit.edu>, Dan Williams <dan.j.williams@intel.com>
CC: "Reshetova, Elena" <elena.reshetova@intel.com>, "Jason A. Donenfeld"
	<Jason@zx2c4.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Dave Hansen <dave.hansen@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>, "x86@kernel.org" <x86@kernel.org>,
	"Kuppuswamy Sathyanarayanan" <sathyanarayanan.kuppuswamy@linux.intel.com>,
	"Nakajima, Jun" <jun.nakajima@intel.com>, Tom Lendacky
	<thomas.lendacky@amd.com>, "Kalra, Ashish" <ashish.kalra@amd.com>, Sean
 Christopherson <seanjc@google.com>, "linux-coco@lists.linux.dev"
	<linux-coco@lists.linux.dev>, "linux-kernel@vger.kernel.org"
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] x86/random: Retry on RDSEED failure
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Theodore Ts'o wrote:
> On Mon, Feb 12, 2024 at 11:28:31PM -0800, Dan Williams wrote:
> > Sure there is, that is what, for example, PCI TDISP (TEE Device
> > Interface Security Protocol) is about. Set aside the difficulty of doing
> > the PCI TDISP flow early in boot, and validating the device certficate
> > and measurements based on golden values without talking to a remote
> > verifier etc..., but if such a device has been accepted and its driver
> > calls hwrng_register() it should be added as an entropy source.
> 
> How real is TDISP?  What hardware exists today and how much of this
> support is ready to land in the kernel?  Looking at the news articles,
> it appears to me like bleeding edge technology, and what an unkind
> person might call "vaporware"?  Is that an unfair characterization?

Indeed it is. Typically when you have x86, riscv, arm, and s390 folks
all show up at a Linux Plumbers session [1] to talk about their approach
to handling a new platform paradigm, that is a decent indication that
the technology is more real than not. Point taken that it is not here
today, but it is also not multiple hardware generations away as the
Plumbers participation indicated.

> There have plenty of things that have squirted out of standards
> bodies, like for example, "objected base storage", which has turned
> out to be a complete commercial failure and was never actually
> deployed in any real numbers, other than sample hardare being provided
> to academic researchers.  How can we be sure that PCI TDISP won't end
> up going down that route?

Of course, that is always a risk. History is littered with obsolesence,
some of it before seeing any commercial uptake, some after.

> In any case, if we are going to go down this path, we will need to
> have some kind of policy engine hwrng_register() reject
> non-authenticated hardware if Confidential Compute is enabled (and
> possibly in other cases).

Sounds reasonable, that recognition is all I wanted from mentioning PCI
TDISP.

[1]: https://lpc.events/event/17/contributions/1633/