linux-kernel - Re: [PATCH v3 06/12] x86/amd_nb: Use topology info to get AMD node count

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Message-ID: <945b3be6-3392-4104-aac1-35d460e40cbb@amd.com>
Date: Thu, 23 Oct 2025 12:12:50 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Michal Pecio <michal.pecio@...il.com>
Cc: Yazen Ghannam <yazen.ghannam@....com>, Shyam-sundar.S-k@....com,
 bhelgaas@...gle.com, hdegoede@...hat.com, ilpo.jarvinen@...ux.intel.com,
 jdelvare@...e.com, linux-edac@...r.kernel.org, linux-hwmon@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, linux@...ck-us.net,
 naveenkrishna.chatradhi@....com, platform-driver-x86@...r.kernel.org,
 suma.hegde@....com, tony.luck@...el.com, x86@...nel.org
Subject: Re: [PATCH v3 06/12] x86/amd_nb: Use topology info to get AMD node
 count

On 10/23/25 12:06 PM, Michal Pecio wrote:
> On Thu, 23 Oct 2025 11:22:29 -0500, Mario Limonciello wrote:
>> As this is an ancient BIOS this reminds me of some related commits:
>>
>> aa06e20f1be6 ("x86/ACPI: Don't add CPUs that are not online capable")
>> a74fabfbd1b70 ("x86/ACPI/boot: Use FADT version to check support for
>> online capable")
>>
>> Does reverting that second one help?
> 
> Not sure if it's worth trying? My BIOS predates the ACPI 6.3 spec by
> several years and (if I understand correctly) MADT revision is 1.
> 
> It seems Yazen guessed right: they list 6 APICs and mark absent ones
> as not enabled. But I don't think we can assume any ACPI 6.3 flags to
> be valid here.
> 
> I wonder if some quick check could recognize those consumer CPUs and
> simply ignore hotplug there? AFAIK it was never a thing on AM3.
> 
> Michal

Oh if the MADT revision is that old, then yeah reverting won't do 
anything here.