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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aS36sX1zP8760L7f@amaterasu.greysector.net>
Date: Mon, 1 Dec 2025 21:29:37 +0100
From: Dominik 'Rathann' Mierzejewski <dominik@...ysector.net>
To: Dave Hansen <dave.hansen@...el.com>
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 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
-- 
Fedora   https://fedoraproject.org
Deep in the human unconscious is a pervasive need for a logical universe that
makes sense. But the real universe is always one step beyond logic.
        -- from "The Sayings of Muad'Dib" by the Princess Irulan