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

[Dominik 'Rathann' Mierzejewski]

On Monday, 01 December 2025 at 18:54, Dave Hansen wrote:
> 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 appreciate the explanation. Buggy BIOSes are a sad fact of life.
Can I fix that with the following?

wrmsr -p 3 0x000001a0 60840488

Would that change anything?

> 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.

Probably not worth any effort, then.

> Are there any ill effects other than the warning splat?

Kernel becomes tainted, which may lead to bug reports of other valid issues
get rejected.

I guess that's my main concern.

Regards,
Dominik
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