linux-kernel - Re: [PATCH 0/6] [v2] x86/cpu: Take Intel platform into account for old microcode checks

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Message-ID: <aYmwSYgWS6bca8iZ@wieczorr-mobl1.localdomain>
Date: Mon, 09 Feb 2026 10:14:21 +0000
From: Maciej Wieczor-Retman <m.wieczorretman@...me>
To: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, sohil.mehta@...el.com, zhao1.liu@...el.com, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Jon Kohler <jon@...anix.com>, Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, "Peter Zijlstra (Intel)" <peterz@...radead.org>, Thomas Gleixner <tglx@...nel.org>, Tony Luck <tony.luck@...el.com>, x86@...nel.org
Subject: Re: [PATCH 0/6] [v2] x86/cpu: Take Intel platform into account for old microcode checks

Retested by fabricating the faulting scenario. After adding the patches the old
microcode warning didn't appear and the microcode entry was correctly matched.

Tested-by: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>

On 2026-02-06 at 15:14:38 -0800, Dave Hansen wrote:
>Changes from v1:
> * Fix non-x86 PECI compile issues by lifting some x86 macros
>   into an arch-independent header.
> * Make intel_get_platform_id() match its name and return an ID,
>   not a mask.
> * Sort #includes
> * Move ->x86_platform_id comment
>
>The platform ID vs. platform mask confusion meant that v1
>worked by total accident. If you tested v1, I'd really
>appreciate you retest this as well.
>
>--
>
>There was a report[1] that CPUs running updated microcode were being
>reported as running old microcode. The reason is that the old
>microcode list neglects to take the platform ID into account.
>
>The platform ID is an Intel-only construct that allows CPUs that
>otherwise have the same model/family/stepping to take different
>microcode revisions. The microcode loader itself already checks this.
>Only the recent "old_microcode" checker failed here.
>
>Treat the platform ID as a peer of model/family/stepping. Store it
>in 'struct cpuinfo_x86', enable matching on it with with 'struct
>x86_cpu_id', and flesh out the 'old_microcode' list with it.
>
>This fixes the report of an inaccurate, false positive in the
>'old_microcode' vulnerability file.
>
>1. https://lore.kernel.org/all/38660F8F-499E-48CD-B58B-4822228A5941@nutanix.com/
>
>Cc: Thomas Gleixner <tglx@...nel.org>
>Cc: Ingo Molnar <mingo@...hat.com>
>Cc: Borislav Petkov <bp@...en8.de>
>Cc: Dave Hansen <dave.hansen@...ux.intel.com>
>Cc: "H. Peter Anvin" <hpa@...or.com>
>Cc: Tony Luck <tony.luck@...el.com>
>Cc: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
>Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
>Cc: x86@...nel.org
>Cc: Jon Kohler <jon@...anix.com>

-- 
Kind regards
Maciej Wieczór-Retman