Hello!
(CC: +Dave Martin)
On 12/06/2025 18:13, 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.
> 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
> +/**
> + * 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.
> + *
> + * 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)
> +{
> + struct acpi_pptt_processor *cpu_node;
> + struct acpi_table_header *table_hdr;
> + struct acpi_subtable_header *entry;
> + bool leaf_flag, has_leaf_flag = false;
> + unsigned long table_end;
> + acpi_status status;
> + u32 proc_sz;
> + int ret = 0;
> +
> + cpumask_clear(cpus);
> +
> + status = acpi_get_table(ACPI_SIG_PPTT, 0, &table_hdr);
> + if (ACPI_FAILURE(status))
> + return 0;
> +
> + if (table_hdr->revision > 1)
> + has_leaf_flag = true;
> +
> + table_end = (unsigned long)table_hdr + table_hdr->length;
> + entry = ACPI_ADD_PTR(struct acpi_subtable_header, table_hdr,
> + sizeof(struct acpi_table_pptt));
> + proc_sz = sizeof(struct acpi_pptt_processor);
> + while ((unsigned long)entry + proc_sz < table_end) {
Dave Martin picked out an off-by-one here - this pattern was copied from other functions,
then fixed while I was still lugging this around out of tree. Should be:
| while ((unsigned long)entry + proc_sz <= table_end) {
See adfab6b39202481bb43286fff94def4953793fdb.
I've fixed this locally.
> + cpu_node = (struct acpi_pptt_processor *)entry;
> + if (entry->type == ACPI_PPTT_TYPE_PROCESSOR &&
> + cpu_node->flags & ACPI_PPTT_ACPI_PROCESSOR_ID_VALID) {
> + leaf_flag = cpu_node->flags & ACPI_PPTT_ACPI_LEAF_NODE;
> + if ((has_leaf_flag && !leaf_flag) ||
> + (!has_leaf_flag && !acpi_pptt_leaf_node(table_hdr, cpu_node))) {
> + if (cpu_node->acpi_processor_id == acpi_cpu_id)
> + acpi_pptt_get_child_cpus(table_hdr, cpu_node, cpus);
> + }
> + }
> + entry = ACPI_ADD_PTR(struct acpi_subtable_header, entry,
> + entry->length);
> + }
> +
> + acpi_put_table(table_hdr);
> +
> + return ret;
> +}
Thanks,
James
