linux-kernel - Re: WARNING: CPU: 1 PID: 0 at arch/x86/kernel/cpu/cpuid-deps.c:123 do_clear_cpu_cap+0xdc/0x130 on Intel(R) Atom(TM) CPU N450 system

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Message-ID: <d0be2023-1dd4-4465-8153-d0f3f426a217@intel.com>
Date: Mon, 1 Dec 2025 09:54:00 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Dominik 'Rathann' Mierzejewski <dominik@...ysector.net>
Cc: Salvatore Bonaccorso <carnil@...ian.org>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 Laurențiu Păncescu <lpancescu@...il.com>,
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
 Sohil Mehta <sohil.mehta@...el.com>, "Chang S. Bae"
 <chang.seok.bae@...el.com>, Andi Kleen <ak@...ux.intel.com>,
 Eric Biggers <ebiggers@...gle.com>, linux-kernel@...r.kernel.org,
 1117002@...s.debian.org
Subject: Re: WARNING: CPU: 1 PID: 0 at arch/x86/kernel/cpu/cpuid-deps.c:123
 do_clear_cpu_cap+0xdc/0x130 on Intel(R) Atom(TM) CPU N450 system

On 11/27/25 04:37, Dominik 'Rathann' Mierzejewski wrote:
>> Could you boot the system on a known good kernel and run this, please?
>>
>> 	rdmsr -a 0x000001a0
>>
>> That'll dump out MSR_IA32_MISC_ENABLE on all the CPUs.
> # rdmsr -a 0x000001a0
> 60840488
> 60840488
> 60840488
> 60840489

I don't think there's any other way to read this than: the BIOS is buggy
and mis-programmed this MSR on one of the CPUs. We can shut the warning
up, of course. But it _is_ a quite valid warning.

I'm just not sure how much code we want to add to the kernel to silence
a warning on 15-year-old CPUs with buggy BIOSes.

Are there any ill effects other than the warning splat?