linux-kernel - Re: Old microcode CPU matching issue - x86/microcode/intel: Refresh the revisions that determine old

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Message-ID: <E8349015-4FF7-4E6B-9A93-61D384619DFB@nutanix.com>
Date: Thu, 20 Nov 2025 16:35:22 +0000
From: Jon Kohler <jon@...anix.com>
To: Dave Hansen <dave.hansen@...el.com>
CC: Sohil Mehta <sohil.mehta@...el.com>,
        Dave Hansen
	<dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, Borislav
 Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar
	<mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra
	<peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Pawan Gupta
	<pawan.kumar.gupta@...ux.intel.com>,
        Nikolay Borisov <nik.borisov@...e.com>,
        Alex Murray <alex.murray@...onical.com>,
        Andrew Cooper
	<andrew.cooper3@...rix.com>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: Old microcode CPU matching issue - x86/microcode/intel: Refresh
 the revisions that determine old_microcode



> On Nov 14, 2025, at 3:34 PM, Dave Hansen <dave.hansen@...el.com> wrote:
> 
> On 10/22/25 10:53, Dave Hansen wrote:
>> I think this is a platform mismatch problem. The microcode file for
>> 06-8f-08 has two different versions for two different platforms:
>> 
>> $ iucode-tool --list-all intel-ucode/06-8f-08 
>> ...
>>           sig 0x000806f8, pf_mask 0x10, 2025-04-08, rev 0x2c000401
>> ...
>>           sig 0x000806f8, pf_mask 0x87, 2025-04-04, rev 0x2b000643
>> 
>> Note the pf_mask and rev deltas here:      ^^^^                  ^^^^^^^^^^
>> 
>> I guess we'll need to take those into consideration, both adding pf_mask to
>> the match list and actually matching on it.
> 
> Jon,
> 
> Here is a completely untested series that might fix your issue:
> 
> https://urldefense.proofpoint.com/v2/url?u=https-3A__git.kernel.org_pub_scm_linux_kernel_git_daveh_devel.git_log_-3Fh-3Dold-2Ducode-2Dplatform&d=DwICaQ&c=s883GpUCOChKOHiocYtGcg&r=NGPRGGo37mQiSXgHKm5rCQ&m=4zPePvFxfJXfp66SgLg_V32bsZLtf6acUOdSXGiOs7nHYrGTY8wvYIsVMdQwGguK&s=RASYUF-4djrYzQOFmSzkZbzpoWsg_qsGHiQJMcLGVhw&e= 
> 
> It attempts to take IA32_PLATFORM_ID into account when considering
> old microcode.

Hey Dave - got a chance to give it a go, and this did not seem to solve
the issue, and in fact it made it kinda worse as I didn’t end up seeing
the microcode getting patched up at all now.

On 6.18 rc6 with a bit of debug logging added, still seeing the same

[    0.000000] x86/CPU: microcode 0x721421856 is older than minimum 0x721421881
[    0.000000] x86/CPU: MATCH LIST DATA: family 0x6, model 0x8f, steppings 0x100
[    0.000000] x86/CPU: BOOT_CPU_DATA: family 0x6, model 0x8f, stepping 0x8
[    0.000000] x86/CPU: Running old microcode
[    3.404176] microcode: Current revision: 0x2b000620 <<<<< I do have 0x2b000643 on the system, but it didn’t give me a notice that it updated early now

This was on this proc:
smpboot: CPU0: Intel(R) Xeon(R) Gold 5416S (family: 0x6, model: 0x8f, stepping: 0x8)

Jon