linux-kernel - Re: Kernel 6.9 regression: X86: Bogus messages from topology detection

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Date: Fri, 31 May 2024 16:29:51 +0200
From: Christian Heusel <christian@...sel.eu>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Schneider <pschneider1968@...glemail.com>, 
	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org, stable@...r.kernel.org, 
	regressions@...ts.linux.dev
Subject: Re: Kernel 6.9 regression: X86: Bogus messages from topology
 detection

On 24/05/31 03:42PM, Thomas Gleixner wrote:
> On Fri, May 31 2024 at 15:08, Christian Heusel wrote:

> > The other person with the i7-1255U in the meantime got back to me with
> > the needed outputs:
> >> - output of cpuid -r
> 
> > 0x0000000b: subleafs:
> >   0: EAX=0x00000001, EBX=0x00000001, ECX=0x00000100, EDX=0x00000012
> >   1: EAX=0x00000006, EBX=0x0000000c, ECX=0x00000201, EDX=0x00000012
> 
> > 0x0000001f: subleafs:
> >   0: EAX=0x00000001, EBX=0x00000001, ECX=0x00000100, EDX=0x00000012
> >   1: EAX=0x00000007, EBX=0x0000000c, ECX=0x00000201, EDX=0x00000012
> 
> So this is inconsistent already. Both leafs should describe the same
> topology. See the differing EAX values (6/7) in subleaf 1, which are
> exactly the values the kernel complains about :)
> 
> But that should not be an issue because the kernel preferres 0x1f over
> 0xb and will never evaluate both, but this is just from one randomly
> picked CPU.
> 
> I wonder which variant of the cpuid tool that is. cpuid -r gives you
> usually just the plain values and collects them for all CPUs.

The previously attached one is output from the version located here:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/arch/x86/kcpuid

The one I have now attached is the one being built from this:
https://www.etallen.com/cpuid.html

Cheers,
Chris

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