[RFC PATCH v3 00/39] ACPI/arm64: add support for virtual cpuhotplug

[Rafael J. Wysocki]

On Tue, Oct 24, 2023 at 5:15 PM Russell King (Oracle)
<linux at armlinux.org.uk> wrote:
>
> Hi,
>
> I'm posting James' patch set updated with most of the review comments
> from his RFC v2 series back in September. Individual patches have a
> changelog attached at the bottom of the commit message. Those which
> I have finished updating have my S-o-b on them, those which still have
> outstanding review comments from RFC v2 do not. In some of these cases
> I've asked questions and am waiting for responses.
>
> I'm posting this as RFC v3 because there's still some unaddressed
> comments and it's clearly not ready for merging. Even if it was ready
> to be merged, it is too late in this development cycle to be taking
> this change in, so there would be little point posting it non-RFC.
> Also James stated that he's waiting for confirmation from the
> Kubernetes/Kata folk - I have no idea what the status is there.
>
> I will be sending each patch individually to a wider audience
> appropriate for that patch - apologies to those missing out on this
> cover message. I have added more mailing lists to the series with the
> exception of the acpica list in a hope of this cover message also
> reaching those folk.
>
> The changes that aren't included are:
>
> 1. Updates for my patch that was merged via Thomas (thanks!):
>    c4dd854f740c cpu-hotplug: Provide prototypes for arch CPU registration
>    rather than having this change spread through James' patches.
>
> 2. New patch - simplification of PA-RISC's smp_prepare_boot_cpu()
>
> 3. Moved "ACPI: Use the acpi_device_is_present() helper in more places"
>    and "ACPI: Rename acpi_scan_device_not_present() to be about
>    enumeration" to the beginning of the series - these two patches are
>    already queued up for merging into 6.7.
>
> 4. Moved "arm64, irqchip/gic-v3, ACPI: Move MADT GICC enabled check into
>    a helper" to the beginning of the series, which has been submitted,
>    but as yet the fate of that posting isn't known.
>
> The first four patches in this series are provided for completness only.
>
> There is an additional patch in James' git tree that isn't in the set
> of patches that James posted: "ACPI: processor: Only call
> arch_unregister_cpu() if HOTPLUG_CPU is selected" which looks to me to
> be a workaround for arch_unregister_cpu() being under the ifdef. I've
> commented on this on the RFC v2 posting making a suggestion, but as yet
> haven't had any response.
>
> I've included almost all of James' original covering body below the
> diffstat.
>
> The reason that I'm doing this is to help move this code forward so
> hopefully it can be merged - which is why I have been keen to dig out
> from James' patches anything that can be merged and submit it
> separately, since this is a feature for which some users have a
> definite need for.

I've gone through the series and there is at least one thing in it
that concerns me a lot and some others that at least appear to be
really questionable.

I need more time to send comments which I'm not going to do before the
6.7 merge window (sorry), but from what I can say right now, this is
not looking good.

Thanks!