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

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Message-ID: <20251023182506.GA796848@yaz-khff2.amd.com>
Date: Thu, 23 Oct 2025 14:25:06 -0400
From: Yazen Ghannam <yazen.ghannam@....com>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Michal Pecio <michal.pecio@...il.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, Oct 23, 2025 at 12:12:50PM -0500, Mario Limonciello wrote:
> 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.
> 

I think this commit is interesting:
fed8d8773b8e ("x86/acpi/boot: Correct acpi_is_processor_usable() check")

Thanks,
Yazen