[PATCH v14 28/32] fs/resctrl: Move RMID initialization to first mount

Tony Luck
2025-11-24T18:55:11Z

L3 monitor features are enumerated during resctrl initialization and
rmid_ptrs[] that tracks all RMIDs and depends on the number of supported
RMIDs is allocated during this time.

Telemetry monitor features are enumerated during first resctrl mount and
may support a different number of RMIDs compared to L3 monitor features.

Delay allocation and initialization of rmid_ptrs[] until first mount.
Since the number of RMIDs cannot change on later mounts, keep the same set of
rmid_ptrs[] until resctrl_exit(). This is required because the limbo handler
keeps running after resctrl is unmounted and needs to access rmid_ptrs[]
as it keeps tracking busy RMIDs after unmount.

Rename routines to match what they now do:
dom_data_init() -> setup_rmid_lru_list()
dom_data_exit() -> free_rmid_lru_list()

Signed-off-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
---
fs/resctrl/internal.h | 4 ++++
fs/resctrl/monitor.c | 54 ++++++++++++++++++++-----------------------
fs/resctrl/rdtgroup.c | 5 ++++
3 files changed, 34 insertions(+), 29 deletions(-)

diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index 399f625be67d..1a9b29119f88 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -369,6 +369,10 @@ int closids_supported(void);

void closid_free(int closid);

+int setup_rmid_lru_list(void);
+
+void free_rmid_lru_list(void);
+
int alloc_rmid(u32 closid);

void free_rmid(u32 closid, u32 rmid);
diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index 55772aeec1a2..bec6a69f2aae 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -896,20 +896,29 @@ void mbm_setup_overflow_handler(struct rdt_l3_mon_domain *dom, unsigned long del
schedule_delayed_work_on(cpu, &dom->mbm_over, delay);
}

-static int dom_data_init(struct rdt_resource *r)
+int setup_rmid_lru_list(void)
{
- u32 idx_limit = resctrl_arch_system_num_rmid_idx();
struct rmid_entry *entry = NULL;
- int err = 0, i;
+ u32 idx_limit;
u32 idx;
+ int i;

- mutex_lock(&rdtgroup_mutex);
+ if (!resctrl_arch_mon_capable())
+ return 0;

+ /*
+ * Called on every mount, but the number of RMIDs cannot change
+ * after the first mount, so keep using the same set of rmid_ptrs[]
+ * until resctrl_exit(). Note that the limbo handler continues to
+ * access rmid_ptrs[] after resctrl is unmounted.
+ */
+ if (rmid_ptrs)
+ return 0;
+
+ idx_limit = resctrl_arch_system_num_rmid_idx();
rmid_ptrs = kcalloc(idx_limit, sizeof(struct rmid_entry), GFP_KERNEL);
- if (!rmid_ptrs) {
- err = -ENOMEM;
- goto out_unlock;
- }
+ if (!rmid_ptrs)
+ return -ENOMEM;

for (i = 0; i < idx_limit; i++) {
entry = &rmid_ptrs[i];
@@ -922,30 +931,24 @@ static int dom_data_init(struct rdt_resource *r)
/*
* RESCTRL_RESERVED_CLOSID and RESCTRL_RESERVED_RMID are special and
* are always allocated. These are used for the rdtgroup_default
- * control group, which will be setup later in resctrl_init().
+ * control group, which was setup earlier in rdtgroup_setup_default().
*/
idx = resctrl_arch_rmid_idx_encode(RESCTRL_RESERVED_CLOSID,
RESCTRL_RESERVED_RMID);
entry = __rmid_entry(idx);
list_del(&entry->list);

-out_unlock:
- mutex_unlock(&rdtgroup_mutex);
-
- return err;
+ return 0;
}

-static void dom_data_exit(struct rdt_resource *r)
+void free_rmid_lru_list(void)
{
- mutex_lock(&rdtgroup_mutex);
-
- if (!r->mon_capable)
- goto out_unlock;
+ if (!resctrl_arch_mon_capable())
+ return;

+ mutex_lock(&rdtgroup_mutex);
kfree(rmid_ptrs);
rmid_ptrs = NULL;
-
-out_unlock:
mutex_unlock(&rdtgroup_mutex);
}

@@ -1823,7 +1826,8 @@ static void closid_num_dirty_rmid_free(void)
* resctrl_l3_mon_resource_init() - Initialise global monitoring structures.
*
* Allocate and initialise global monitor resources that do not belong to a
- * specific domain. i.e. the rmid_ptrs[] used for the limbo and free lists.
+ * specific domain. i.e. the closid_num_dirty_rmid[] used to find the CLOSID
+ * with the cleanest set of RMIDs.
* Called once during boot after the struct rdt_resource's have been configured
* but before the filesystem is mounted.
* Resctrl's cpuhp callbacks may be called before this point to bring a domain
@@ -1843,12 +1847,6 @@ int resctrl_l3_mon_resource_init(void)
if (ret)
return ret;

- ret = dom_data_init(r);
- if (ret) {
- closid_num_dirty_rmid_free();
- return ret;
- }
-
if (resctrl_arch_is_evt_configurable(QOS_L3_MBM_TOTAL_EVENT_ID)) {
mon_event_all[QOS_L3_MBM_TOTAL_EVENT_ID].configurable = true;
resctrl_file_fflags_init("mbm_total_bytes_config",
@@ -1895,6 +1893,4 @@ void resctrl_l3_mon_resource_exit(void)
return;

closid_num_dirty_rmid_free();
-
- dom_data_exit(r);
}
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index e95d3d0dc515..d49ffc56ea61 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -2799,6 +2799,10 @@ static int rdt_get_tree(struct fs_context *fc)
goto out;
}

+ ret = setup_rmid_lru_list();
+ if (ret)
+ goto out;
+
ret = rdtgroup_setup_root(ctx);
if (ret)
goto out;
@@ -4654,4 +4658,5 @@ void resctrl_exit(void)
*/

resctrl_l3_mon_resource_exit();
+ free_rmid_lru_list();
}
--
2.51.1