On Fri, 11 Jul 2025 18:36:20 +0000
James Morse <james.morse@arm.com> wrote:
> MPAM identifies CPUs by the cache_id in the PPTT cache structure.
>
> The driver needs to know which CPUs are associated with the cache,
> the CPUs may not all be online, so cacheinfo does not have the
> information.
>
> Add a helper to pull this information out of the PPTT.
>
> CC: Rohit Mathew <Rohit.Mathew@arm.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
> drivers/acpi/pptt.c | 70 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/acpi.h | 6 ++++
> 2 files changed, 76 insertions(+)
>
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index f53748a5df19..81f7ac18c023 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -985,3 +985,73 @@ int find_acpi_cache_level_from_id(u32 cache_id)
> acpi_put_table(table);
> return -ENOENT;
> }
> +
> +/**
> + * acpi_pptt_get_cpumask_from_cache_id() - Get the cpus associated with the
> + * specified cache
> + * @cache_id: The id field of the unified cache
> + * @cpus: Where to build the cpumask
> + *
> + * Determine which CPUs are below this cache in the PPTT. This allows the property
> + * to be found even if the CPUs are offline.
> + *
> + * The PPTT table must be rev 3 or later,
> + *
> + * Return: -ENOENT if the PPTT doesn't exist, or the cache cannot be found.
> + * Otherwise returns 0 and sets the cpus in the provided cpumask.
> + */
> +int acpi_pptt_get_cpumask_from_cache_id(u32 cache_id, cpumask_t *cpus)
> +{
> + u32 acpi_cpu_id;
> + acpi_status status;
> + int level, cpu, num_levels;
> + struct acpi_pptt_cache *cache;
> + struct acpi_table_header *table;
> + struct acpi_pptt_cache_v1 *cache_v1;
> + struct acpi_pptt_processor *cpu_node;
> +
> + cpumask_clear(cpus);
> +
> + status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
Similar suggestions to previous patch apply here as well.
> + if (ACPI_FAILURE(status)) {
> + acpi_pptt_warn_missing();
> + return -ENOENT;
> + }
> +
> + if (table->revision < 3) {
> + acpi_put_table(table);
> + return -ENOENT;
> + }
> +
> + /*
> + * If we found the cache first, we'd still need to walk from each cpu.
> + */
> + for_each_possible_cpu(cpu) {
> + acpi_cpu_id = get_acpi_id_for_cpu(cpu);
> + cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
> + if (!cpu_node)
> + break;
> + acpi_count_levels(table, cpu_node, &num_levels, NULL);
> +
> + /* Start at 1 for L1 */
> + for (level = 1; level <= num_levels; level++) {
> + cache = acpi_find_cache_node(table, acpi_cpu_id,
> + ACPI_PPTT_CACHE_TYPE_UNIFIED,
> + level, &cpu_node);
> + if (!cache)
> + continue;
> +
> + cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1,
> + cache,
> + sizeof(struct acpi_pptt_cache));
> +
> + if (cache->flags & ACPI_PPTT_CACHE_ID_VALID &&
> + cache_v1->cache_id == cache_id) {
> + cpumask_set_cpu(cpu, cpus);
> + }
Unnecessary {} Fine to keep them if you add something else here later.
> + }
> + }
> +
> + acpi_put_table(table);
> + return 0;
> +}
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 82947f6d2a43..61ac3d1de1e8 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -1543,6 +1543,7 @@ int find_acpi_cpu_topology_package(unsigned int cpu);
> int find_acpi_cpu_topology_hetero_id(unsigned int cpu);
> int acpi_pptt_get_cpus_from_container(u32 acpi_cpu_id, cpumask_t *cpus);
> int find_acpi_cache_level_from_id(u32 cache_id);
> +int acpi_pptt_get_cpumask_from_cache_id(u32 cache_id, cpumask_t *cpus);
> #else
> static inline int acpi_pptt_cpu_is_thread(unsigned int cpu)
> {
> @@ -1573,6 +1574,11 @@ static inline int find_acpi_cache_level_from_id(u32 cache_id)
> {
> return -EINVAL;
> }
> +static inline int acpi_pptt_get_cpumask_from_cache_id(u32 cache_id,
> + cpumask_t *cpus)
> +{
> + return -EINVAL;
> +}
> #endif
>
> void acpi_arch_init(void);