Re: [PATCH 1/4] ACPI / PPTT: Add a helper to fill a cpumask from a processor container

[Sudeep Holla <sudeep.holla@arm.com>]

On Thu, Jun 12, 2025 at 05:13:33PM +0000, James Morse wrote:
> The PPTT describes CPUs and caches, as well as processor containers.
> The ACPI table for MPAM describes the set of CPUs that can access an MSC
> with the UID of a processor container.
> 
> Add a helper to find the processor container by its id, then walk
> the possible CPUs to fill a cpumask with the CPUs that have this
> processor container as a parent.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
>  drivers/acpi/pptt.c  | 91 ++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/acpi.h |  6 +++
>  2 files changed, 97 insertions(+)
> 
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index 54676e3d82dd..aaf9b5a26d07 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -298,6 +298,97 @@ static struct acpi_pptt_processor *acpi_find_processor_node(struct acpi_table_he
>  	return NULL;
>  }
>  
> +/**
> + * acpi_pptt_get_child_cpus() - Find all the CPUs below a PPTT processor node
> + * @table_hdr:		A reference to the PPTT table.
> + * @parent_node:	A pointer to the processor node in the @table_hdr.
> + * @cpus:		A cpumask to fill with the CPUs below @parent_node.
> + *

Is this cpus mask always cleared before acpi_pptt_get_child_cpus() is called.
Just checking if it makes sense to clear it before we start the loop in this
function or do we have a need to start with a pre-filled cpumask ?

Other than that, LGTM.

Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>

-- 
Regards,
Sudeep