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

[Jeremy Linton <jeremy.linton@arm.com>]

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@arm.com> 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.