Re: [PATCH v2 3/3] arm64: disable ACPI PPTT support temporarily

[Jeremy Linton]

Hi,

On 06/05/2018 10:27 AM, Sudeep Holla wrote:
> On 05/06/18 16:02, Rafael J. Wysocki wrote:
> > On Tue, Jun 5, 2018 at 4:35 PM, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
> > > Currently, ARM64 doesn't support updating the CPU topology masks on
> > > CPU hotplug operations. ACPI PPTT support rely on that missing feature
> > > which is technically not incorrect. Instead of reverting all the PPTT
> > > support, let's keep it simple and disable ACPI PPTT support on ARM64
> > > for time-being until the topology updates are added for CPU hotplug
> > > operations.
> >
> > When is that going to happen?
> > > Nobody else uses PPTT now.
>
> No we need it on ARM64. I have even the fixes for the original issue
> but it's bit invasive and too late as we are already in the merge
> window. It needs to be tested on NUMA platforms, I have asked for that
> explicitly.

So, there is a lot simpler fix for this, and its to remove the numa mask 
dependency from the scheduler domain building. That is just a couple 
line fix, and it reverts !ACPI to its original behavior, while the ACPI 
LLC building will work around the NUMA in package issue that caused 
patch 12/12 as the machine in question doesn't have a LLC crossing numa 
domains.