[PATCH v3 19/47] arm_mpam: resctrl: Implement helpers to update configuration

Ben Horgan
2026-01-12T17:01:36Z

From: James Morse <james.morse@arm.com>

resctrl has two helpers for updating the configuration.
resctrl_arch_update_one() updates a single value, and is used by the
software-controller to apply feedback to the bandwidth controls, it has to
be called on one of the CPUs in the resctrl:domain.

resctrl_arch_update_domains() copies multiple staged configurations, it can
be called from anywhere.

Both helpers should update any changes to the underlying hardware.

Implement resctrl_arch_update_domains() to use
resctrl_arch_update_one(). Neither need to be called on a specific CPU as
the mpam driver will send IPIs as needed.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
list_for_each_entry -> list_for_each_entry_rcu
return 0
Restrict scope of local variables

Changes since v2:
whitespace fix
---
drivers/resctrl/mpam_resctrl.c | 70 ++++++++++++++++++++++++++++++++++
1 file changed, 70 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 25012e779509..5b73fe45b8fa 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -212,6 +212,76 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_ctrl_domain *d,
}
}

+int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_ctrl_domain *d,
+ u32 closid, enum resctrl_conf_type t, u32 cfg_val)
+{
+ u32 partid;
+ struct mpam_config cfg;
+ struct mpam_props *cprops;
+ struct mpam_resctrl_res *res;
+ struct mpam_resctrl_dom *dom;
+
+ lockdep_assert_cpus_held();
+ lockdep_assert_irqs_enabled();
+
+ /*
+ * No need to check the CPU as mpam_apply_config() doesn't care, and
+ * resctrl_arch_update_domains() relies on this.
+ */
+ res = container_of(r, struct mpam_resctrl_res, resctrl_res);
+ dom = container_of(d, struct mpam_resctrl_dom, resctrl_ctrl_dom);
+ cprops = &res->class->props;
+
+ partid = resctrl_get_config_index(closid, t);
+ if (!r->alloc_capable || partid >= resctrl_arch_get_num_closid(r)) {
+ pr_debug("Not alloc capable or computed PARTID out of range\n");
+ return -EINVAL;
+ }
+
+ /*
+ * Copy the current config to avoid clearing other resources when the
+ * same component is exposed multiple times through resctrl.
+ */
+ cfg = dom->ctrl_comp->cfg[partid];
+
+ switch (r->rid) {
+ case RDT_RESOURCE_L2:
+ case RDT_RESOURCE_L3:
+ cfg.cpbm = cfg_val;
+ mpam_set_feature(mpam_feat_cpor_part, &cfg);
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return mpam_apply_config(dom->ctrl_comp, partid, &cfg);
+}
+
+int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid)
+{
+ int err;
+ struct rdt_ctrl_domain *d;
+
+ lockdep_assert_cpus_held();
+ lockdep_assert_irqs_enabled();
+
+ list_for_each_entry_rcu(d, &r->ctrl_domains, hdr.list) {
+ for (enum resctrl_conf_type t = 0; t < CDP_NUM_TYPES; t++) {
+ struct resctrl_staged_config *cfg = &d->staged_config[t];
+
+ if (!cfg->have_new_ctrl)
+ continue;
+
+ err = resctrl_arch_update_one(r, d, closid, t,
+ cfg->new_ctrl);
+ if (err)
+ return err;
+ }
+ }
+
+ return 0;
+}
+
void resctrl_arch_reset_all_ctrls(struct rdt_resource *r)
{
struct mpam_resctrl_res *res;
--
2.43.0