linux-kernel - Re: [PATCH 1/2] x86/random: Retry on RDSEED failure

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Message-ID: <CAHmME9rum4uwSNFd_GkD9p_+vN4DBxA=feZX7k9RvugFZsZNJg@mail.gmail.com>
Date: Tue, 30 Jan 2024 19:35:36 +0100
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: "Reshetova, Elena" <elena.reshetova@...el.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, 
	"x86@...nel.org" <x86@...nel.org>, "Theodore Ts'o" <tytso@....edu>, 
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>, 
	"Nakajima, Jun" <jun.nakajima@...el.com>, Tom Lendacky <thomas.lendacky@....com>, 
	"Kalra, Ashish" <ashish.kalra@....com>, Sean Christopherson <seanjc@...gle.com>, 
	"linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] x86/random: Retry on RDSEED failure

Elena,

On Tue, Jan 30, 2024 at 3:06 PM Jason A. Donenfeld <Jason@...c4.com> wrote:
> 2) Can a malicious host *actually* create a fully deterministic
> environment? One that'll produce the same timing for the jitter
> entropy creation, and all the other timers and interrupts and things?
> I imagine the attestation part of CoCo means these VMs need to run on
> real Intel silicon and so it can't be single stepped in TCG or
> something, right? So is this problem actually a real one? And to what
> degree? Any good experimental research on this?

I'd like to re-up this question. It seems like assessing the reality
of the concern would be worthwhile.

Jason