Re: [PATCH] ACPI/PPTT: use ACPI ID whenever ACPI_PPTT_ACPI_PROCESSOR_ID_VALID is set

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

Hi,

On 07/02/2018 04:57 AM, Sudeep Holla wrote:
> 
> 
> On 02/07/18 10:06, Rafael J. Wysocki wrote:
>> On Fri, Jun 29, 2018 at 6:17 PM, Sudeep Holla <sudeep.holla@arm.com> wrote:
>>> Currently we use the ACPI processor ID only for the leaf/processor nodes
>>> as the specification states it must match the value of ACPI processor ID
>>> field in the processor’s entry in the MADT.
>>>
>>> However, if a PPTT structure represents processors group, it match a
>>> processor container UID in the namespace and ACPI_PPTT_ACPI_PROCESSOR_ID_VALID
>>> flag describe whether the ACPI processor ID is valid.
>>>
>>> Lets use UID whenever ACPI_PPTT_ACPI_PROCESSOR_ID_VALID is set to be
>>> consistent instead of using table offset as it's currently done for non
>>> leaf nodes.
>>>
>>> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
>>> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
>>> ---
>>>   drivers/acpi/pptt.c | 10 ++++++++--
>>>   1 file changed, 8 insertions(+), 2 deletions(-)
>>>
>>> Hi,
>>>
>>> There's ongoing discussion on assigning ID based in OS using simple
>>> counters. It can never be consistent with firmware's view. So if the
>>> firmware provides valid UID for non-processors node, we must use it.
>>
>> OK
>>
>> Do you regard this as a fix for the recently merged PPTT material?  If
>> so, I should apply it as a fix for 4.18.
>>
> 
> Yes, it should be considered as fix IMO.

Do we know which machines are affected?

I'm mostly agnostic to this patch because I believe its effectively a 
NOP. But that said, it could have a functional change, which implies 
there is some risk.