linux-kernel - Re: [tip: x86/urgent] x86/CPU/AMD: Add RDSEED fix for Zen5

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Message-ID: <aQPdJ7CbIRI6dj0Q@zx2c4.com>
Date: Thu, 30 Oct 2025 22:48:23 +0100
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: linux-kernel@...r.kernel.org
Cc: linux-tip-commits@...r.kernel.org, stable@...r.kernel.org,
	Gregory Price <gourry@...rry.net>,
	"Borislav Petkov (AMD)" <bp@...en8.de>, x86@...nel.org
Subject: Re: [tip: x86/urgent] x86/CPU/AMD: Add RDSEED fix for Zen5

On Thu, Oct 30, 2025 at 07:05:16PM +0100, Jason A. Donenfeld wrote:
> I didn't see this on LKML or any mailing list before this appeared in
> tip. Did I miss something?

Also, by the way,

Link: https://www.amd.com/en/resources/product-security/bulletin/amd-sb-7055.html
> Until the microcode patch is deployed, the following software
> workaround options could be used: 
>
> [...]
>
> - Software can treat RDSEED returning 0 equivalent to when CF=0. Retry
>   RDSEED later until a non-zero value is returned with CF=1

You sure that's such a good idea?

Jason