linux-kernel - Re: Early boot regression from f0551af0213 ("x86/topology: Ignore non-present APIC IDs in a present package")

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Date: Thu, 25 Apr 2024 11:56:40 -0400
From: Lyude Paul <lyude@...hat.com>
To: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: Early boot regression from f0551af0213 ("x86/topology: Ignore
 non-present APIC IDs in a present package")

Yep - tried booting a kernel with f0551af0213 reverted and
possible_cpus=8, it definitely looks like that crashes things as well
in the same way. Also - it scrolled off the screen before I had a
chance to write it down, but I'm -fairly- sure I saw some sort of
complaint about "16 [or some double digit number] processors exceeds
max number of 8". Which is quite interesting, as this is definitely
just a quad core ryzen processor with hyperthreading - so there should
only be 8 threads.

On Thu, 2024-04-25 at 04:11 +0200, Thomas Gleixner wrote:
> Lyude!
> 
> On Wed, Apr 24 2024 at 16:56, Lyude Paul wrote:
> > On Sat, 2024-04-20 at 00:15 +0200, Thomas Gleixner wrote:
> > Lyude is fine BTW :P (I get the confusion though, Paul is usually
> > not a
> > last name lol)
> 
> :)
> 
> > Anyway - unfortunately it doesn't seem like this patch helps :s,
> > I'm
> > still not seeing any difference and the backtrace I'm seeing at
> > early
> > boot looks the same. Any more information I can provide?
> 
> Can you please boot a kernel with the commit in question reverted and
> add 'possible_cpus=8' to the kernel command line?
> 
> In theory this should fail too.
> 
> Thanks,
> 
>         tglx
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat