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

[Jeremy Linton]

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@xxxxxxx> 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 processorâs 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@xxxxxxxxxxxxx>
> > > Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
> > > ---
> > >   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.