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

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Message-ID: <87plt26m2b.ffs@tglx>
Date: Fri, 31 May 2024 17:25:00 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Christian Heusel <christian@...sel.eu>
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 Fri, May 31 2024 at 16:29, Christian Heusel wrote:

P-Cores are consistent:

> CPU 0:
>    0x0000000b 0x01: eax=0x00000006 ebx=0x0000000c ecx=0x00000201 edx=0x00000000

>    0x0000001f 0x00: eax=0x00000001 ebx=0x00000002 ecx=0x00000100 edx=0x00000000

E-Cores are not:

> CPU 4:
>    0x0000000b 0x01: eax=0x00000006 ebx=0x0000000c ecx=0x00000201 edx=0x00000010

>    0x0000001f 0x01: eax=0x00000007 ebx=0x0000000c ecx=0x00000201 edx=0x00000010

As the topology is evaluated from CPU0 CPUID leaf 0x1f it's obvious that
CPU4...11 will trigger the sanity checks because their CPUID leaf 0x1f
subleaf 1 entries are bogus.

IOW it's a firmware bug and there is nothing the kernel will and can do
about it except what it does already: complaining about the inconsistency.

Thanks for providing all the information!

       tglx