linux-kernel - Re: AMD zen microcode updates breaks boot

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Message-ID: <aaf25389-e0c3-408a-ae05-a166c1720bf8@kernel.dk>
Date: Fri, 18 Oct 2024 10:47:35 -0600
From: Jens Axboe <axboe@...nel.dk>
To: "Dr. David Alan Gilbert" <linux@...blig.org>,
 Borislav Petkov <bp@...en8.de>
Cc: Thomas Gleixner <tglx@...utronix.de>,
 the arch/x86 maintainers <x86@...nel.org>,
 LKML <linux-kernel@...r.kernel.org>,
 "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>
Subject: Re: AMD zen microcode updates breaks boot

On 10/18/24 10:45 AM, Dr. David Alan Gilbert wrote:
> * Borislav Petkov (bp@...en8.de) wrote:
>> On Fri, Oct 18, 2024 at 07:30:15AM -0600, Jens Axboe wrote:
>>> At least on mine, the BIOS has an option that says something like "L3
>>> cache as numa domain", which is on and why there's 32 nodes on that box.
>>> It's pretty handy for testing since there's a crap ton of CPUs, as it
>>> makes affinity handling easier.
>>
>> Right, so two boxes I tested with this:
>>
>> * 2 socket, a bit different microcode:
>>
>> [   22.947525] smp: Brought up 32 nodes, 512 CPUs
>>
>> * your CPU, one socket:
>>
>> [   26.830137] smp: Brought up 16 nodes, 255 CPUs
> 
> (Probably unrelated but...)
> What happened to number 256 ?

Quick guess, maybe iommu was off, will cap it to 255. IIRC...

-- 
Jens Axboe