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

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Message-ID: <176221415302.318632.4870393502359325240@copycat>
Date: Mon, 03 Nov 2025 15:55:53 -0800
From: Christopher Snowhill <chris@...e54.net>
To: Borislav Petkov <bp@...en8.de>
Cc: "Jason A. Donenfeld" <Jason@...c4.com>, 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 Mon 03 Nov 2025 01:03:19 PM , Borislav Petkov wrote:
> On Mon, Nov 03, 2025 at 02:22:44AM -0800, Christopher Snowhill wrote:
> > Although apparently, the patch does break userspace for any distribution
> > building packages with -march=znver4
> 
> Care to elaborate?

Sorry for the HTML before, apparently I'm not supposed to try writing
replies from my tablet, because it will interpret the quote indenting as
formatting and forcibly send HTML mail.

Anyway. A bug report was sent here:

https://lore.kernel.org/lkml/9a27f2e6-4f62-45a6-a527-c09983b8dce4@cachyos.org/

Qt is built with -march=znver4, which automatically enables -mrdseed.
This is building rdseed 64 bit, but then the software is also performing
kernel feature checks on startup. There is no separate feature flag for
16/32/64 variants.

> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette

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