On Thu, 7 Sep 2023, Jan Beulich wrote: > On 06.09.2023 22:49, Stefano Stabellini wrote: > > On Fri, 1 Sep 2023, Jan Beulich wrote: > >> 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 <[email protected]> > >> > >> 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 am in favor of downgrading physical CPU hotplug support in > > SUPPORT.md. > > > > I noticed that there is no entry for physical CPU hotplug support in > > SUPPORT.md today. Should we assume that it is not supported already as > > it is not listed as supported? > > Hmm, I see > > ## Host hardware support > > ### Physical CPU Hotplug > > Status, x86: Supported > > pretty close to the top of the file.
Ops, it must have been the case-sensitive search that failed me > > Specifically, would it be a good idea to add a sentence at the top of > > the file saying that anything not explicitly listed is not supported? > > Iirc that was the plan to do for 4.18, but then we need to be sure that > things don't unintentionally become unsupported. I've no clear idea how > this plan was meant to be carried out, though. it would be interesting to discuss it again
