Hi, On 06/29/2018 11:17 AM, Sudeep Holla 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" <r...@rjwysocki.net> Signed-off-by: Sudeep Holla <sudeep.ho...@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. Regards, Sudeep diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c index e5ea1974d1e3..d1e26cb599bf 100644 --- a/drivers/acpi/pptt.c +++ b/drivers/acpi/pptt.c @@ -481,8 +481,14 @@ static int topology_get_acpi_cpu_tag(struct acpi_table_header *table, if (cpu_node) { cpu_node = acpi_find_processor_package_id(table, cpu_node, level, flag); - /* Only the first level has a guaranteed id */ - if (level == 0) + /* + * As per specification if the processor structure represents + * an actual processor, then ACPI processor ID must be valid. + * For processor containers ACPI_PPTT_ACPI_PROCESSOR_ID_VALID + * should be set if the UID is valid + */ + if (level == 0 || + cpu_node->flags & ACPI_PPTT_ACPI_PROCESSOR_ID_VALID) return cpu_node->acpi_processor_id;
While, for some machines this likely helps create more human readable ID's... What happens when the ID namespaces conflict with each other?
AKA, I'm a little shy of this change because your going from something we can guarantee is unique to depending on an portion of the PPTT definition that has a couple different ways that it can be interpreted.
OTOH the change is probably safe at the moment because i don't think anyone has partially marked nodes at a given PPTT "level" valid, or put structures that aren't part of the PE/cache's in the tree (outside of my juno test tree with the GPU's/etc).
