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

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Message-ID: <176216536464.37138.975167391934381427@copycat>
Date: Mon, 03 Nov 2025 02:22:44 -0800
From: Christopher Snowhill <chris@...e54.net>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: Borislav Petkov <bp@...en8.de>, 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 Sun 19 Oct 2025 05:03:25 PM , Jason A. Donenfeld wrote:
> On Sun, Oct 19, 2025 at 05:00:27PM +0200, Borislav Petkov wrote:
> > On Sun, Oct 19, 2025 at 04:46:06PM +0200, Jason A. Donenfeld wrote:
> > > While your team is checking into this, I'd be most interested to know
> > > one way or the other whether this affects RDRAND too.
> > 
> > No it doesn't, AFAIK. The only one affected is the 32-bit or 16-bit dest
> > operand version of RDSEED. Again, AFAIK.
> 
> Oh good. So on 64-bit kernels, the impact to random.c is zilch.
> 
> Jason
>

Although apparently, the patch does break userspace for any distribution
building packages with -march=znver4

- Christopher

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