[PATCH v2 39/45] arm_mpam: resctrl: Call resctrl_init() on platforms that can support resctrl

Ben Horgan
2025-12-19T18:15:09Z

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

Now that MPAM links against resctrl, call resctrl_init() to register the
filesystem and setup resctrl's structures.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
drivers/resctrl/mpam_devices.c | 32 +++++++++++--
drivers/resctrl/mpam_internal.h | 4 ++
drivers/resctrl/mpam_resctrl.c | 82 ++++++++++++++++++++++++++++++++-
3 files changed, 113 insertions(+), 5 deletions(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 4f5d908d02a9..c20b2757b86b 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -73,6 +73,14 @@ static DECLARE_WORK(mpam_broken_work, &mpam_disable);
/* When mpam is disabled, the printed reason to aid debugging */
static char *mpam_disable_reason;

+/*
+ * Whether resctrl has been setup. Used by cpuhp in preference to
+ * mpam_is_enabled(). The disable call after an error interrupt makes
+ * mpam_is_enabled() false before the cpuhp callbacks are made.
+ * Reads/writes should hold mpam_cpuhp_state_lock, (or be cpuhp callbacks).
+ */
+static bool mpam_resctrl_enabled;
+
/*
* An MSC is a physical container for controls and monitors, each identified by
* their RIS index. These share a base-address, interrupts and some MMIO
@@ -1628,7 +1636,7 @@ static int mpam_cpu_online(unsigned int cpu)
mpam_reprogram_msc(msc);
}

- if (mpam_is_enabled())
+ if (mpam_resctrl_enabled)
mpam_resctrl_online_cpu(cpu);

return 0;
@@ -1674,7 +1682,7 @@ static int mpam_cpu_offline(unsigned int cpu)
{
struct mpam_msc *msc;

- if (mpam_is_enabled())
+ if (mpam_resctrl_enabled)
mpam_resctrl_offline_cpu(cpu);

guard(srcu)(&mpam_srcu);
@@ -2536,6 +2544,7 @@ static void mpam_enable_once(void)
}

static_branch_enable(&mpam_enabled);
+ mpam_resctrl_enabled = true;
mpam_register_cpuhp_callbacks(mpam_cpu_online, mpam_cpu_offline,
"mpam:online");

@@ -2595,24 +2604,39 @@ void mpam_reset_class(struct mpam_class *class)
void mpam_disable(struct work_struct *ignored)
{
int idx;
+ bool do_resctrl_exit;
struct mpam_class *class;
struct mpam_msc *msc, *tmp;

+ if (mpam_is_enabled())
+ static_branch_disable(&mpam_enabled);
+
mutex_lock(&mpam_cpuhp_state_lock);
if (mpam_cpuhp_state) {
cpuhp_remove_state(mpam_cpuhp_state);
mpam_cpuhp_state = 0;
}
+
+ /*
+ * Removing the cpuhp state called mpam_cpu_offline() and told resctrl
+ * all the CPUs are offline.
+ */
+ do_resctrl_exit = mpam_resctrl_enabled;
+ mpam_resctrl_enabled = false;
mutex_unlock(&mpam_cpuhp_state_lock);

- static_branch_disable(&mpam_enabled);
+ if (do_resctrl_exit)
+ mpam_resctrl_exit();

mpam_unregister_irqs();

idx = srcu_read_lock(&mpam_srcu);
list_for_each_entry_srcu(class, &mpam_classes, classes_list,
- srcu_read_lock_held(&mpam_srcu))
+ srcu_read_lock_held(&mpam_srcu)) {
mpam_reset_class(class);
+ if (do_resctrl_exit)
+ mpam_resctrl_teardown_class(class);
+ }
srcu_read_unlock(&mpam_srcu, idx);

mutex_lock(&mpam_list_lock);
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index b907bec96ba5..9a3996decda5 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -447,12 +447,16 @@ int mpam_get_cpumask_from_cache_id(unsigned long cache_id, u32 cache_level,

#ifdef CONFIG_RESCTRL_FS
int mpam_resctrl_setup(void);
+void mpam_resctrl_exit(void);
int mpam_resctrl_online_cpu(unsigned int cpu);
void mpam_resctrl_offline_cpu(unsigned int cpu);
+void mpam_resctrl_teardown_class(struct mpam_class *class);
#else
static inline int mpam_resctrl_setup(void) { return 0; }
+static inline void mpam_resctrl_exit(void) { }
static inline int mpam_resctrl_online_cpu(unsigned int cpu) { return 0; }
static inline void mpam_resctrl_offline_cpu(unsigned int cpu) { }
+static inline void mpam_resctrl_teardown_class(struct mpam_class *class) { }
#endif /* CONFIG_RESCTRL_FS */

/*
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 059148c38a38..bbb12b5dfd8c 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -53,6 +53,12 @@ static bool exposed_mon_capable;
*/
static bool cdp_enabled;

+/*
+ * If resctrl_init() succeeded, resctrl_exit() can be used to remove support
+ * for the filesystem in the event of an error.
+ */
+static bool resctrl_enabled;
+
/*
* mpam_resctrl_pick_caches() needs to know the size of the caches. cacheinfo
* populates this from a device_initcall(). mpam_resctrl_setup() must wait.
@@ -318,6 +324,9 @@ static int resctrl_arch_mon_ctx_alloc_no_wait(enum resctrl_event_id evtid)
{
struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[evtid];

+ if (!mpam_is_enabled())
+ return -EINVAL;
+
if (!mon->class)
return -EINVAL;

@@ -360,6 +369,9 @@ static void resctrl_arch_mon_ctx_free_no_wait(enum resctrl_event_id evtid,
{
struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[evtid];

+ if (!mpam_is_enabled())
+ return;
+
if (!mon->class)
return;

@@ -461,6 +473,9 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_mon_domain *d,

resctrl_arch_rmid_read_context_check();

+ if (!mpam_is_enabled())
+ return -EINVAL;
+
if (eventid >= QOS_NUM_EVENTS || !mon->class)
return -EINVAL;

@@ -1399,6 +1414,9 @@ int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_ctrl_domain *d,
lockdep_assert_cpus_held();
lockdep_assert_irqs_enabled();

+ if (!mpam_is_enabled())
+ return -EINVAL;
+
/*
* No need to check the CPU as mpam_apply_config() doesn't care, and
* resctrl_arch_update_domains() relies on this.
@@ -1461,6 +1479,9 @@ int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid)
lockdep_assert_cpus_held();
lockdep_assert_irqs_enabled();

+ if (!mpam_is_enabled())
+ return -EINVAL;
+
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];
@@ -1840,11 +1861,70 @@ int mpam_resctrl_setup(void)
pr_warn("Number of PMG is not a power of 2! resctrl may misbehave");
}

- /* TODO: call resctrl_init() */
+ err = resctrl_init();
+ if (!err)
+ WRITE_ONCE(resctrl_enabled, true);

return err;
}

+void mpam_resctrl_exit(void)
+{
+ if (!READ_ONCE(resctrl_enabled))
+ return;
+
+ WRITE_ONCE(resctrl_enabled, false);
+ resctrl_exit();
+}
+
+static void mpam_resctrl_teardown_mon(struct mpam_resctrl_mon *mon, struct mpam_class *class)
+{
+ u32 num_mbwu_mon = l3_num_allocated_mbwu;
+
+ if (!mon->mbwu_idx_to_mon)
+ return;
+
+ if (mon->assigned_counters) {
+ __free_mbwu_mon(class, mon->assigned_counters, num_mbwu_mon);
+ mon->assigned_counters = NULL;
+ kfree(mon->mbwu_idx_to_mon);
+ } else {
+ __free_mbwu_mon(class, mon->mbwu_idx_to_mon, num_mbwu_mon);
+ }
+ mon->mbwu_idx_to_mon = NULL;
+}
+
+/*
+ * The driver is detaching an MSC from this class, if resctrl was using it,
+ * pull on resctrl_exit().
+ */
+void mpam_resctrl_teardown_class(struct mpam_class *class)
+{
+ int i;
+ struct mpam_resctrl_res *res;
+ struct mpam_resctrl_mon *mon;
+
+ might_sleep();
+
+ for (i = 0; i < RDT_NUM_RESOURCES; i++) {
+ res = &mpam_resctrl_controls[i];
+ if (res->class == class) {
+ res->class = NULL;
+ break;
+ }
+ }
+ for (i = 0; i < QOS_NUM_EVENTS; i++) {
+ mon = &mpam_resctrl_counters[i];
+ if (mon->class == class) {
+ mon->class = NULL;
+
+ mpam_resctrl_teardown_mon(mon, class);
+
+ break;
+ }
+ }
+}
+
static int __init __cacheinfo_ready(void)
{
cacheinfo_ready = true;
--
2.43.0