Re: [XEN PATCH] x86/ACPI: Ignore entries with invalid APIC IDs when parsing MADT

[Jan Beulich <jbeulich@xxxxxxxx>]

On 07.08.2023 11:38, Simon Gaiser wrote:
> It seems some firmwares put dummy entries in the ACPI MADT table for non
> existing processors. On my NUC11TNHi5 those have the invalid APIC ID
> 0xff. Linux already has code to handle those cases both in
> acpi_parse_lapic [1] as well as in acpi_parse_x2apic [2]. So add the
> same check to Xen.
> 
> Note that on some older (2nd gen Core i) laptop of mine I also saw dummy
> entries with a valid APIC ID. Linux would still ignore those because
> they have !ACPI_MADT_ENABLED && !ACPI_MADT_ONLINE_CAPABLE. But in Xen
> this check is only active for madt_revision >= 5. But since this version
> check seems to be intentionally I leave that alone.
> 
> Link: 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f3bf1dbe64b62a2058dd1944c00990df203e8e7a
>  # [1]
> Link: 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=10daf10ab154e31237a8c07242be3063fb6a9bf4
>  # [2]
> Signed-off-by: Simon Gaiser <simon@xxxxxxxxxxxxxxxxxxxxxx>

This patch was committed with unaddressed review comments. The normal action
in such a case would be to revert, expecting a v2 to arrive. One alternative
here would be a timely incremental patch submission. Another alternative,
considering in particular Thomas's most recent reply, would be to properly
downgrade CPU hotplug support in SUPPORT.md (with a corresponding entry in
CHANGELOG.md).

I'll give it until the end of next week for either of the alternatives to be
carried out. If nothing appears by then, I'll assume I may rightfully revert.
(This timeline also allows putting this topic on the Community Call agenda,
should anyone think this is necessary.)

Regards, Jan