Re: [PATCH AUTOSEL 6.6 02/17] x86/acpi: Ignore invalid x2APIC entries

[Andres Freund]

Hi,

On 2023-11-22 10:31:31 -0500, Sasha Levin wrote:
> From: Zhang Rui <rui.zhang@xxxxxxxxx>
>
> [ Upstream commit ec9aedb2aa1ab7ac420c00b31f5edc5be15ec167 ]
>
> Currently, the kernel enumerates the possible CPUs by parsing both ACPI
> MADT Local APIC entries and x2APIC entries. So CPUs with "valid" APIC IDs,
> even if they have duplicated APIC IDs in Local APIC and x2APIC, are always
> enumerated.

As just described in
https://lore.kernel.org/all/20231206065850.hs7k554v6wym7gw5@xxxxxxxxxxxxxxxxxx/
and also previously described by John Sperbeck
https://lore.kernel.org/all/20231122221947.781812-1-jsperbeck@xxxxxxxxxx/

this patch causes some machines to "loose" cpus. All but one in my case.


Even if the commit didn't have these unintended consequences, it seems like a
commit like this hardly is -stable material?

- Andres