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>
Tested-by: Fenghua Yu <fenghuay@nvidia.com>
---
Changes since v2:
* Removed stray cleanup useage in preference for acpi_get_pptt().
* Removed WARN_ON_ONCE() for symmetry with other helpers.
* Dropped restriction on unified caches.
Changes since v1:
* Added punctuation to the commit message.
* Removed a comment about an alternative implementaion.
* Made the loop continue with a warning if a CPU is missing from the PPTT.
Changes since RFC:
* acpi_count_levels() now returns a value.
* Converted the table-get stuff to use Jonathan's cleanup helper.
* Dropped Sudeep's Review tag due to the cleanup change.
---
drivers/acpi/pptt.c | 64 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/acpi.h | 6 +++++
2 files changed, 70 insertions(+)
diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index 50c8f2a3c927..2f86f58699a6 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -985,3 +985,67 @@ 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 level, cpu;
+ u32 acpi_cpu_id;
+ 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);
+
+ table = acpi_get_pptt();
+ if (!table)
+ return -ENOENT;
+
+ if (table->revision < 3)
+ return -ENOENT;
+
+ 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)
+ continue;
+
+ /* Start at 1 for L1 */
+ level = 1;
+ cache = acpi_find_any_type_cache_node(table, acpi_cpu_id, level,
+ &cpu_node);
+ while (cache) {
+ cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1,
+ cache, sizeof(*cache));
+ if (!cache)
+ continue;
+
+ cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1,
+ cache, sizeof(*cache));
+
+ if (cache->flags & ACPI_PPTT_CACHE_ID_VALID &&
+ cache_v1->cache_id == cache_id)
+ cpumask_set_cpu(cpu, cpus);
+
+ level++;
+ cache = acpi_find_any_type_cache_node(table, acpi_cpu_id,
+ level, &cpu_node);
+ }
+ }
+
+ 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);
--
2.39.5Hi,
This is largely looking pretty solid, but..
On 10/17/25 1:56 PM, James Morse 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>
> Tested-by: Fenghua Yu <fenghuay@nvidia.com>
> ---
> Changes since v2:
> * Removed stray cleanup useage in preference for acpi_get_pptt().
> * Removed WARN_ON_ONCE() for symmetry with other helpers.
> * Dropped restriction on unified caches.
>
> Changes since v1:
> * Added punctuation to the commit message.
> * Removed a comment about an alternative implementaion.
> * Made the loop continue with a warning if a CPU is missing from the PPTT.
>
> Changes since RFC:
> * acpi_count_levels() now returns a value.
> * Converted the table-get stuff to use Jonathan's cleanup helper.
> * Dropped Sudeep's Review tag due to the cleanup change.
> ---
> drivers/acpi/pptt.c | 64 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/acpi.h | 6 +++++
> 2 files changed, 70 insertions(+)
>
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index 50c8f2a3c927..2f86f58699a6 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -985,3 +985,67 @@ 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 level, cpu;
> + u32 acpi_cpu_id;
> + 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);
> +
> + table = acpi_get_pptt();
> + if (!table)
> + return -ENOENT;
> +
> + if (table->revision < 3)
> + return -ENOENT;
> +
> + 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)
> + continue;
> +
> + /* Start at 1 for L1 */
> + level = 1;
> + cache = acpi_find_any_type_cache_node(table, acpi_cpu_id, level,
> + &cpu_node);
> + while (cache) {
> + cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1,
> + cache, sizeof(*cache));
Is the core acpi definition in actbl2.h correct? Shouldn't it be
something along the lines of:
struct acpi_pptt_cache_v1 {
struct acpi_subtable_header header;
u16 reservedd;
u32 flags;
u32 next_level_of_cache;
u32 size;
u32 number_of_sets;
u8 associativity;
u8 attributes;
u16 lines_size;
u32 cache_id;
}
Then that solves the detection of the additional field problem correctly
because the length (24 vs 28) of the subtable then tells you which
version your dealing with. (and goes back to why much of this is coded
to use ACPI_ADD_PTR rather than structure+ logic.)
Thanks,
> + if (!cache)
> + continue;
> +
> + cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1,
> + cache, sizeof(*cache));
> +
> + if (cache->flags & ACPI_PPTT_CACHE_ID_VALID &&
> + cache_v1->cache_id == cache_id)
> + cpumask_set_cpu(cpu, cpus);
> +
> + level++;
> + cache = acpi_find_any_type_cache_node(table, acpi_cpu_id,
> + level, &cpu_node);
> + }
> + }
> +
> + 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);
On Wed, 22 Oct 2025 07:58:36 -0500
Jeremy Linton <jeremy.linton@arm.com> wrote:
> Hi,
>
> This is largely looking pretty solid, but..
>
>
> On 10/17/25 1:56 PM, James Morse 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>
> > Tested-by: Fenghua Yu <fenghuay@nvidia.com>
> > ---
> > Changes since v2:
> > * Removed stray cleanup useage in preference for acpi_get_pptt().
> > * Removed WARN_ON_ONCE() for symmetry with other helpers.
> > * Dropped restriction on unified caches.
> >
> > Changes since v1:
> > * Added punctuation to the commit message.
> > * Removed a comment about an alternative implementaion.
> > * Made the loop continue with a warning if a CPU is missing from the PPTT.
> >
> > Changes since RFC:
> > * acpi_count_levels() now returns a value.
> > * Converted the table-get stuff to use Jonathan's cleanup helper.
> > * Dropped Sudeep's Review tag due to the cleanup change.
> > ---
> > drivers/acpi/pptt.c | 64 ++++++++++++++++++++++++++++++++++++++++++++
> > include/linux/acpi.h | 6 +++++
> > 2 files changed, 70 insertions(+)
> >
> > diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> > index 50c8f2a3c927..2f86f58699a6 100644
> > --- a/drivers/acpi/pptt.c
> > +++ b/drivers/acpi/pptt.c
> > @@ -985,3 +985,67 @@ 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 level, cpu;
> > + u32 acpi_cpu_id;
> > + 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);
> > +
> > + table = acpi_get_pptt();
> > + if (!table)
> > + return -ENOENT;
> > +
> > + if (table->revision < 3)
> > + return -ENOENT;
> > +
> > + 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)
> > + continue;
> > +
> > + /* Start at 1 for L1 */
> > + level = 1;
> > + cache = acpi_find_any_type_cache_node(table, acpi_cpu_id, level,
> > + &cpu_node);
> > + while (cache) {
> > + cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1,
> > + cache, sizeof(*cache));
>
> Is the core acpi definition in actbl2.h correct? Shouldn't it be
> something along the lines of:
>
> struct acpi_pptt_cache_v1 {
> struct acpi_subtable_header header;
> u16 reservedd;
> u32 flags;
> u32 next_level_of_cache;
> u32 size;
> u32 number_of_sets;
> u8 associativity;
> u8 attributes;
> u16 lines_size;
> u32 cache_id;
> }
>
>
> Then that solves the detection of the additional field problem correctly
> because the length (24 vs 28) of the subtable then tells you which
> version your dealing with. (and goes back to why much of this is coded
> to use ACPI_ADD_PTR rather than structure+ logic.)
>
Do we want to deal with arguing the change in ACPICA?
I fully agree that it would be much nicer if that didn't use this weird
bits of structures approach :(
https://github.com/acpica/acpica/blob/master/source/include/actbl2.h#L3497
is where this is coming from.
Maybe can do it in parallel. Rafael, what do you think is best way forwards
with this?
Jonathan
>
> Thanks,
>
>
>
>
>
>
> > + if (!cache)
> > + continue;
> > +
> > + cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1,
> > + cache, sizeof(*cache));
> > +
> > + if (cache->flags & ACPI_PPTT_CACHE_ID_VALID &&
> > + cache_v1->cache_id == cache_id)
> > + cpumask_set_cpu(cpu, cpus);
> > +
> > + level++;
> > + cache = acpi_find_any_type_cache_node(table, acpi_cpu_id,
> > + level, &cpu_node);
> > + }
> > + }
> > +
> > + 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);
>
>
Hi Jonathan, Jeremy,
(Replying for James as I'll post the next version of this series.)
On 10/24/25 15:22, Jonathan Cameron wrote:
> On Wed, 22 Oct 2025 07:58:36 -0500
> Jeremy Linton <jeremy.linton@arm.com> wrote:
>
>> Hi,
>>
>> This is largely looking pretty solid, but..
>>
>>
>> On 10/17/25 1:56 PM, James Morse 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>
>>> Tested-by: Fenghua Yu <fenghuay@nvidia.com>
>>> ---
[...]
>>
>> Is the core acpi definition in actbl2.h correct? Shouldn't it be
>> something along the lines of:
>>
>> struct acpi_pptt_cache_v1 {
>> struct acpi_subtable_header header;
>> u16 reservedd;
>> u32 flags;
>> u32 next_level_of_cache;
>> u32 size;
>> u32 number_of_sets;
>> u8 associativity;
>> u8 attributes;
>> u16 lines_size;
>> u32 cache_id;
>> }
>>
>>
>> Then that solves the detection of the additional field problem correctly
>> because the length (24 vs 28) of the subtable then tells you which
>> version your dealing with. (and goes back to why much of this is coded
>> to use ACPI_ADD_PTR rather than structure+ logic.)
>>
>
> Do we want to deal with arguing the change in ACPICA?
> I fully agree that it would be much nicer if that didn't use this weird
> bits of structures approach :(
For the moment I've added:
struct acpi_pptt_cache_v1_full {
struct acpi_pptt_cache f;
struct acpi_pptt_cache_v1 extra;
} __packed;
in drivers/acpi/pptt.c
A stop gap but the length can be used to check for field presence and
you can avoid some ACPI_ADD_PTR usages.
>
> https://github.com/acpica/acpica/blob/master/source/include/actbl2.h#L3497
> is where this is coming from.
>
> Maybe can do it in parallel. Rafael, what do you think is best way forwards
> with this?
>
> Jonathan
Thanks,
Ben
Hi James,
On 10/17/25 19:56, James Morse 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>
> Tested-by: Fenghua Yu <fenghuay@nvidia.com>
> ---
> Changes since v2:
> * Removed stray cleanup useage in preference for acpi_get_pptt().
> * Removed WARN_ON_ONCE() for symmetry with other helpers.
> * Dropped restriction on unified caches.
>
> Changes since v1:
> * Added punctuation to the commit message.
> * Removed a comment about an alternative implementaion.
> * Made the loop continue with a warning if a CPU is missing from the PPTT.
>
> Changes since RFC:
> * acpi_count_levels() now returns a value.
> * Converted the table-get stuff to use Jonathan's cleanup helper.
> * Dropped Sudeep's Review tag due to the cleanup change.
> ---
> drivers/acpi/pptt.c | 64 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/acpi.h | 6 +++++
> 2 files changed, 70 insertions(+)
>
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index 50c8f2a3c927..2f86f58699a6 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -985,3 +985,67 @@ 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 level, cpu;
> + u32 acpi_cpu_id;
> + 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);
> +
> + table = acpi_get_pptt();
> + if (!table)
> + return -ENOENT;
> +
> + if (table->revision < 3)
> + return -ENOENT;
> +
> + 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)
> + continue;
> +
> + /* Start at 1 for L1 */
> + level = 1;
> + cache = acpi_find_any_type_cache_node(table, acpi_cpu_id, level,
> + &cpu_node);
> + while (cache) {
> + cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1,
> + cache, sizeof(*cache));
> + if (!cache)
> + continue;
> +
> + cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1,
> + cache, sizeof(*cache));
> +
> + if (cache->flags & ACPI_PPTT_CACHE_ID_VALID &&
> + cache_v1->cache_id == cache_id)
> + cpumask_set_cpu(cpu, cpus);
> +
> + level++;
Same comment as for the previous patch. You are bumping the level
without considering if there is another cache at that level.
> + cache = acpi_find_any_type_cache_node(table, acpi_cpu_id,
> + level, &cpu_node);
> + }
> + }
> +
> + return 0;
> +}
Thanks,
Ben
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