Re: [PATCH v2 20/29] arm_mpam: Allow configuration to be applied and restored during cpu online

Jonathan Cameron
2025-09-12T12:22:34Z

On Wed, 10 Sep 2025 20:43:00 +0000
James Morse <james.morse@arm.com> wrote:

> When CPUs come online the MSC's original configuration should be restored.
>
> Add struct mpam_config to hold the configuration. This has a bitmap of
> features that were modified. Once the maximum partid is known, allocate
> a configuration array for each component, and reprogram each RIS
> configuration from this.
>
> CC: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: James Morse <james.morse@arm.com>
Trivial comments
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> +
> +static void mpam_init_reset_cfg(struct mpam_config *reset_cfg)
> +{
> + memset(reset_cfg, 0, sizeof(*reset_cfg));

Might as well do the following and skip the memset.

*reset_cfg = (struct mpam_config) {
.features = ~0,
.cpbm = ~0,
.mbw_pbm = ~0,
.mbw_max = MPAM...
.reset_cpbm = true,
.reset_mbw_pbm = true,
};
> +
> + reset_cfg->features = ~0;
> + reset_cfg->cpbm = ~0;
> + reset_cfg->mbw_pbm = ~0;
> + reset_cfg->mbw_max = MPAMCFG_MBW_MAX_MAX;
> +
> + reset_cfg->reset_cpbm = true;
> + reset_cfg->reset_mbw_pbm = true;
> +}

> +static int mpam_allocate_config(void)
> +{
> + int err = 0;

Always set before use. Maybe push down so it is in tighter scope and
can declare and initialize to final value in one line.

> + struct mpam_class *class;
> + struct mpam_component *comp;
> +
> + lockdep_assert_held(&mpam_list_lock);
> +
> + list_for_each_entry(class, &mpam_classes, classes_list) {
> + list_for_each_entry(comp, &class->components, class_list) {
> + err = __allocate_component_cfg(comp);
> + if (err)
> + return err;
> + }
> + }
> +
> + return 0;
> +}

> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
> index b69fa9199cb4..17570d9aae9b 100644
> --- a/drivers/resctrl/mpam_internal.h
> +++ b/drivers/resctrl/mpam_internal.h
> @@ -169,11 +169,7 @@ struct mpam_props {
> u16 num_mbwu_mon;
> };
>
> -static inline bool mpam_has_feature(enum mpam_device_features feat,
> - struct mpam_props *props)
> -{
> - return (1 << feat) & props->features;
> -}
> +#define mpam_has_feature(_feat, x) ((1 << (_feat)) & (x)->features)

If this is worth doing push it back to original introduction.
I'm not sure it is necessary.

Jonathan