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

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Message-ID: <20251023190644.114bf9f8.michal.pecio@gmail.com>
Date: Thu, 23 Oct 2025 19:06:44 +0200
From: Michal Pecio <michal.pecio@...il.com>
To: Mario Limonciello <mario.limonciello@....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 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