linux-kernel - Re: [PATCH 2/2] x86/random: Issue a warning if RDRAND or RDSEED fails

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Message-ID: <a076974c-e2c7-43c9-9858-71c913361cea@intel.com>
Date: Tue, 30 Jan 2024 09:58:09 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: "Reshetova, Elena" <elena.reshetova@...el.com>,
 "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 2/2] x86/random: Issue a warning if RDRAND or RDSEED fails

On 1/30/24 09:49, Jason A. Donenfeld wrote:
>> Anybody disagree?
> Yes, I disagree. I made a trivial test that shows RDSEED breaks easily
> in a busy loop. So at the very least, your statement holds true only
> for RDRAND.

Well, darn. :)

Any chance you could share some more information about the environment
where you're seeing this?  It'd be good to reconcile what you're seeing
with how the hardware is expected to behave.