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Message-ID: <92f99246-1533-4bf9-bbb5-39d1c148467f@arm.com>
Date: Wed, 19 Nov 2025 10:37:29 -0600
From: Jeremy Linton <jeremy.linton@....com>
To: Ben Horgan <ben.horgan@....com>, james.morse@....com
Cc: amitsinght@...vell.com, baisheng.gao@...soc.com,
baolin.wang@...ux.alibaba.com, bobo.shaobowang@...wei.com,
carl@...amperecomputing.com, catalin.marinas@....com, dakr@...nel.org,
dave.martin@....com, david@...hat.com, dfustini@...libre.com,
fenghuay@...dia.com, gregkh@...uxfoundation.org, gshan@...hat.com,
guohanjun@...wei.com, jonathan.cameron@...wei.com, kobak@...dia.com,
lcherian@...vell.com, lenb@...nel.org, linux-acpi@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
lpieralisi@...nel.org, peternewman@...gle.com, quic_jiles@...cinc.com,
rafael@...nel.org, robh@...nel.org, rohit.mathew@....com,
scott@...amperecomputing.com, sdonthineni@...dia.com, sudeep.holla@....com,
tan.shaopeng@...itsu.com, will@...nel.org, xhao@...ux.alibaba.com,
Zeng Heng <zengheng4@...wei.com>, Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Subject: Re: [PATCH v5 05/34] ACPI / PPTT: Add a helper to fill a cpumask from
a cache_id
On 11/17/25 10:59 AM, Ben Horgan wrote:
> From: James Morse <james.morse@....com>
>
> 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.
All the PPTT stuff look fine to me, patch 4+5 continue to build on some
of the copy/pasty bits in this module which isn't ideal but seems to be
the best way forward at the moment.
Reviewed-by: Jeremy Linton <jeremy.linton@....com>
Thanks again for taking care of this.
>
> CC: Rohit Mathew <Rohit.Mathew@....com>
> Reviewed-by: Gavin Shan <gshan@...hat.com>
> Reviewed-by: Fenghua Yu <fenghuay@...dia.com>
> Tested-by: Fenghua Yu <fenghuay@...dia.com>
> Tested-by: Carl Worth <carl@...amperecomputing.com>
> Tested-by: Gavin Shan <gshan@...hat.com>
> Tested-by: Zeng Heng <zengheng4@...wei.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> Signed-off-by: James Morse <james.morse@....com>
> Signed-off-by: Ben Horgan <ben.horgan@....com>
> ---
> Changes since v4:
> Same changes as previous patch in series
> do/while
> initialisation of acpi_cpu_id
> use new version of acpi_pptt_cache_v1_full
>
> Changes since v3:
> Equivalent changes to the previous patch:
> Tags dropped due to rework
> Fallout/simplification from adding acpi_pptt_cache_v1_full
> Look for each cache type before incrementing level
> ---
> drivers/acpi/pptt.c | 65 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/acpi.h | 6 ++++
> 2 files changed, 71 insertions(+)
>
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index 5b1e9e410204..cea80337f01f 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -998,3 +998,68 @@ int find_acpi_cache_level_from_id(u32 cache_id)
>
> return -ENOENT;
> }
> +
> +/**
> + * acpi_pptt_get_cpumask_from_cache_id() - Get the cpus associated with the
> + * specified cache
> + * @cache_id: The id field of the 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)
> +{
> + int cpu;
> + struct acpi_table_header *table;
> +
> + cpumask_clear(cpus);
> +
> + table = acpi_get_pptt();
> + if (!table)
> + return -ENOENT;
> +
> + if (table->revision < 3)
> + return -ENOENT;
> +
> + for_each_possible_cpu(cpu) {
> + bool empty;
> + int level = 1;
> + u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
> + struct acpi_pptt_cache *cache;
> + struct acpi_pptt_processor *cpu_node;
> +
> + cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
> + if (!cpu_node)
> + continue;
> +
> + do {
> + int cache_type[] = {CACHE_TYPE_INST, CACHE_TYPE_DATA, CACHE_TYPE_UNIFIED};
> +
> + empty = true;
> + for (int i = 0; i < ARRAY_SIZE(cache_type); i++) {
> + struct acpi_pptt_cache_v1_full *cache_v1;
> +
> + cache = acpi_find_cache_node(table, acpi_cpu_id, cache_type[i],
> + level, &cpu_node);
> +
> + if (!cache)
> + continue;
> +
> + empty = false;
> +
> + cache_v1 = upgrade_pptt_cache(cache);
> + if (cache_v1 && cache_v1->cache_id == cache_id)
> + cpumask_set_cpu(cpu, cpus);
> + }
> + level++;
> + } while (!empty);
> + }
> +
> + return 0;
> +}
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index be074bdfd4d1..a9dbacabdf89 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);
> void 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)
> {
> @@ -1570,6 +1571,11 @@ static inline int find_acpi_cache_level_from_id(u32 cache_id)
> {
> return -ENOENT;
> }
> +static inline int acpi_pptt_get_cpumask_from_cache_id(u32 cache_id,
> + cpumask_t *cpus)
> +{
> + return -ENOENT;
> +}
> #endif
>
> void acpi_arch_init(void);
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