Re: [PATCH v2 22/29] arm_mpam: Add helpers to allocate monitors

Jonathan Cameron
2025-09-12T13:11:28Z

On Wed, 10 Sep 2025 20:43:02 +0000
James Morse <james.morse@arm.com> wrote:

> MPAM's MSC support a number of monitors, each of which supports
> bandwidth counters, or cache-storage-utilisation counters. To use
> a counter, a monitor needs to be configured. Add helpers to allocate
> and free CSU or MBWU monitors.
>
> Signed-off-by: James Morse <james.morse@arm.com>
> Reviewed-by: Ben Horgan <ben.horgan@arm.com>

One minor requested change inline that will probably otherwise get picked
up by someone's cleanup script

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---
> drivers/resctrl/mpam_devices.c | 2 ++
> drivers/resctrl/mpam_internal.h | 35 +++++++++++++++++++++++++++++++++
> 2 files changed, 37 insertions(+)
>
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index f536ebbcf94e..cf190f896de1 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -340,6 +340,8 @@ mpam_class_alloc(u8 level_idx, enum mpam_class_types type)
> class->level = level_idx;
> class->type = type;
> INIT_LIST_HEAD_RCU(&class->classes_list);
> + ida_init(&class->ida_csu_mon);
> + ida_init(&class->ida_mbwu_mon);
>
> list_add_rcu(&class->classes_list, &mpam_classes);
>
> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
> index 326ba9114d70..81c4c2bfea3d 100644
> --- a/drivers/resctrl/mpam_internal.h
> +++ b/drivers/resctrl/mpam_internal.h
> @@ -210,6 +210,9 @@ struct mpam_class {
> /* member of mpam_classes */
> struct list_head classes_list;
>
> + struct ida ida_csu_mon;
> + struct ida ida_mbwu_mon;
> +
> struct mpam_garbage garbage;
> };
>
> @@ -288,6 +291,38 @@ struct mpam_msc_ris {
> struct mpam_garbage garbage;
> };
>
> +static inline int mpam_alloc_csu_mon(struct mpam_class *class)
> +{
> + struct mpam_props *cprops = &class->props;
> +
> + if (!mpam_has_feature(mpam_feat_msmon_csu, cprops))
> + return -EOPNOTSUPP;
> +
> + return ida_alloc_range(&class->ida_csu_mon, 0, cprops->num_csu_mon - 1,
> + GFP_KERNEL);
> +}
> +
> +static inline void mpam_free_csu_mon(struct mpam_class *class, int csu_mon)
> +{
> + ida_free(&class->ida_csu_mon, csu_mon);
> +}
> +
> +static inline int mpam_alloc_mbwu_mon(struct mpam_class *class)
> +{
> + struct mpam_props *cprops = &class->props;
> +
> + if (!mpam_has_feature(mpam_feat_msmon_mbwu, cprops))
> + return -EOPNOTSUPP;
> +
> + return ida_alloc_range(&class->ida_mbwu_mon, 0,
> + cprops->num_mbwu_mon - 1, GFP_KERNEL);

ida_alloc_max() - which is just a wrapper that sets the minimum to 0
but none the less perhaps conveys things slightly better.

> +}
> +
> +static inline void mpam_free_mbwu_mon(struct mpam_class *class, int mbwu_mon)
> +{
> + ida_free(&class->ida_mbwu_mon, mbwu_mon);
> +}
> +
> /* List of all classes - protected by srcu*/
> extern struct srcu_struct mpam_srcu;
> extern struct list_head mpam_classes;