linux-kernel - Re: [PATCH v2] x86/amd: Disable RDSEED on AMD Zen5 because of an error.

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Message-ID: <27717271.1r3eYUQgxm@tjmaciei-mobl5>
Date: Fri, 07 Nov 2025 15:11:51 -0800
From: Thiago Macieira <thiago.macieira@...el.com>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: Borislav Petkov <bp@...en8.de>, Christopher Snowhill <chris@...e54.net>,
 Gregory Price <gourry@...rry.net>, x86@...nel.org,
 linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
 dave.hansen@...ux.intel.com, hpa@...or.com, peterz@...radead.org,
 mario.limonciello@....com, riel@...riel.com, yazen.ghannam@....com,
 me@...aill.net, kai.huang@...el.com, sandipan.das@....com,
 darwi@...utronix.de, stable@...r.kernel.org
Subject:
 Re: [PATCH v2] x86/amd: Disable RDSEED on AMD Zen5 because of an error.

On Friday, 7 November 2025 15:07:13 Pacific Standard Time Jason A. Donenfeld 
wrote:
> Oh. "Entropy source draining" is not a real thing. There used to be
> bizarre behavior related to /dev/random (not urandom), but this has been
> gone for ages. And even the non-getrandom Linux fallback code uses
> /dev/urandom before /dev/random. So not even on old kernels is this an
> issue. You can keep generating random numbers forever without worrying
> about running out of juice or irritating other processes.

Thank you. This probably seals the deal. I'll prepare a patch removing the 
direct use of the hardware instructions in the coming days.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Principal Engineer - Intel DCG - Platform & Sys. Eng.

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