linux-kernel - Re: [RFC PATCH 05/36] ACPI / PPTT: Add a helper to fill a cpumask from a processor container

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Message-ID: <20250722152807.000069d3@huawei.com>
Date: Tue, 22 Jul 2025 15:28:07 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: James Morse <james.morse@....com>
CC: <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	"Rob Herring" <robh@...nel.org>, Ben Horgan <ben.horgan@....com>, Rohit
 Mathew <rohit.mathew@....com>, Shanker Donthineni <sdonthineni@...dia.com>,
	"Zeng Heng" <zengheng4@...wei.com>, Lecopzer Chen <lecopzerc@...dia.com>,
	"Carl Worth" <carl@...amperecomputing.com>,
	<shameerali.kolothum.thodi@...wei.com>, D Scott Phillips OS
	<scott@...amperecomputing.com>, <lcherian@...vell.com>,
	<bobo.shaobowang@...wei.com>, <tan.shaopeng@...itsu.com>,
	<baolin.wang@...ux.alibaba.com>, Jamie Iles <quic_jiles@...cinc.com>, Xin Hao
	<xhao@...ux.alibaba.com>, <peternewman@...gle.com>, <dfustini@...libre.com>,
	<amitsinght@...vell.com>, David Hildenbrand <david@...hat.com>, Rex Nie
	<rex.nie@...uarmicro.com>, Dave Martin <dave.martin@....com>, Koba Ko
	<kobak@...dia.com>, Sudeep Holla <sudeep.holla@....com>
Subject: Re: [RFC PATCH 05/36] ACPI / PPTT: Add a helper to fill a cpumask
 from a processor container

On Fri, 11 Jul 2025 18:36:17 +0000
James Morse <james.morse@....com> 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.
> 
> CC: Dave Martin <dave.martin@....com>
> Reviewed-by: Sudeep Holla <sudeep.holla@....com>
> Signed-off-by: James Morse <james.morse@....com>


> +/**
> + * acpi_pptt_get_cpus_from_container() - Populate a cpumask with all CPUs in a
> + *                                       processor containers
> + * @acpi_cpu_id:	The UID of the processor container.
> + * @cpus		The resulting CPU mask.
Missing colon.

From a W=1 build (and hence kernel-doc warning).
> + *
> + * Find the specified Processor Container, and fill @cpus with all the cpus
> + * below it.
> + *
> + * Not all 'Processor' entries in the PPTT are either a CPU or a Processor
> + * Container, they may exist purely to describe a Private resource. CPUs
> + * have to be leaves, so a Processor Container is a non-leaf that has the
> + * 'ACPI Processor ID valid' flag set.
> + *
> + * Return: 0 for a complete walk, or an error if the mask is incomplete.
> + */
> +int acpi_pptt_get_cpus_from_container(u32 acpi_cpu_id, cpumask_t *cpus)