[PATCH v8 next 08/10] arm_mpam: Implement dynamic reqPARTID allocation for monitoring groups

Zeng Heng
2026-04-13T08:55:26Z

Replace static reqPARTID allocation with dynamic binding to maximize
the monitoring group utilization. Static allocation wastes resources when
control groups create fewer sub-groups than the pre-allocated limit.

Add a lookup table (reqpartid_map) to dynamically bind reqPARTIDs to
control groups needing extended monitoring capacity:

* resctrl_arch_rmid_expand(): Find and bind a free reqPARTID to the
specified closid when creating monitoring groups.

* resctrl_arch_rmid_reclaim(): Unbind reqPARTID when all monitoring
groups associated with pmg are freed, making it available for reuse.

Update conversion helpers for dynamic mapping:
* req2intpartid() switches to lookup table for dynamic allocation.
* Add partid2closid() and req_pmg2rmid() helpers.

Refactor __write_config() to iterate over all reqPARTIDs that match
by intPARTID, removing fixed per-closid slot assumption.

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
---
drivers/resctrl/mpam_devices.c | 21 ++---
drivers/resctrl/mpam_internal.h | 2 +
drivers/resctrl/mpam_resctrl.c | 141 +++++++++++++++++++++++++++++---
include/linux/arm_mpam.h | 17 ++++
4 files changed, 157 insertions(+), 24 deletions(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 2aeff798a865..cf94b45b4f9e 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -1764,27 +1764,24 @@ struct mpam_write_config_arg {
u16 partid;
};

-static u32 get_num_reqpartid_per_intpartid(void)
-{
- return (mpam_partid_max + 1) / (mpam_intpartid_max + 1);
-}
-
static int __write_config(void *arg)
{
int closid_num = resctrl_arch_get_num_closid(NULL);
struct mpam_write_config_arg *c = arg;
- u32 reqpartid, req_idx;
+ u32 reqpartid;

/* c->partid should be within the range of intPARTIDs */
WARN_ON_ONCE(c->partid >= closid_num);

- /* Synchronize the configuration to each sub-monitoring group. */
- for (req_idx = 0; req_idx < get_num_reqpartid_per_intpartid();
- req_idx++) {
- reqpartid = req_idx * closid_num + c->partid;
+ mpam_reprogram_ris_partid(c->ris, c->partid,
+ &c->comp->cfg[c->partid]);

- mpam_reprogram_ris_partid(c->ris, reqpartid,
- &c->comp->cfg[c->partid]);
+ /* Synchronize the configuration to each sub-monitoring group. */
+ for (reqpartid = closid_num;
+ reqpartid < get_num_reqpartid(); reqpartid++) {
+ if (req2intpartid(reqpartid) == c->partid)
+ mpam_reprogram_ris_partid(c->ris, reqpartid,
+ &c->comp->cfg[c->partid]);
}

return 0;
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 790a90a5ccd9..16ce968344d0 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -473,6 +473,8 @@ void mpam_msmon_reset_mbwu(struct mpam_component *comp, struct mon_cfg *ctx);
int mpam_get_cpumask_from_cache_id(unsigned long cache_id, u32 cache_level,
cpumask_t *affinity);

+u32 get_num_reqpartid(void);
+
#ifdef CONFIG_RESCTRL_FS
int mpam_resctrl_setup(void);
void mpam_resctrl_exit(void);
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 9d0a7a4dffd1..2762462d80e5 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -268,7 +268,7 @@ u32 resctrl_arch_get_num_closid(struct rdt_resource *ignored)
* The first call occurs in update_rmid_limits(), ensuring the
* prerequisite initialization is complete.
*/
-static u32 get_num_reqpartid(void)
+u32 get_num_reqpartid(void)
{
struct mpam_resctrl_res *res;
struct mpam_props *cprops;
@@ -318,9 +318,34 @@ static u8 rmid2pmg(u32 rmid)
return rmid % (mpam_pmg_max + 1);
}

+static u32 req_pmg2rmid(u32 reqpartid, u8 pmg)
+{
+ if (cdp_enabled)
+ reqpartid >>= 1;
+
+ return reqpartid * (mpam_pmg_max + 1) + pmg;
+}
+
+static u32 *reqpartid_map;
+
u16 req2intpartid(u16 reqpartid)
{
- return reqpartid % (mpam_intpartid_max + 1);
+ /*
+ * Directly return intPartid in case that mpam_reset_ris() access
+ * NULL pointer.
+ */
+ if (reqpartid < (mpam_intpartid_max + 1))
+ return reqpartid;
+
+ return reqpartid_map[reqpartid];
+}
+
+static u32 partid2closid(u32 partid)
+{
+ if (cdp_enabled)
+ partid >>= 1;
+
+ return partid;
}

/*
@@ -334,12 +359,12 @@ u16 req2intpartid(u16 reqpartid)
u32 resctrl_arch_rmid_idx_encode(u32 closid, u32 rmid)
{
u32 reqpartid = rmid2reqpartid(rmid);
- u32 intpartid = req2intpartid(reqpartid);

- if (cdp_enabled)
- intpartid >>= 1;
+ /* When enable CDP mode, needs to filter invalid rmid entry out */
+ if (reqpartid >= get_num_reqpartid())
+ return U32_MAX;

- if (closid != intpartid)
+ if (closid != partid2closid(req2intpartid(reqpartid)))
return U32_MAX;

return rmid;
@@ -352,11 +377,9 @@ void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid)

if (rmid)
*rmid = idx;
- if (closid) {
- if (cdp_enabled)
- intpartid >>= 1;
- *closid = intpartid;
- }
+
+ if (closid)
+ *closid = partid2closid(intpartid);
}

void resctrl_arch_sched_in(struct task_struct *tsk)
@@ -1665,6 +1688,93 @@ void mpam_resctrl_offline_cpu(unsigned int cpu)
}
}

+static int reqpartid_init(void)
+{
+ int req_num, idx;
+
+ req_num = get_num_reqpartid();
+ reqpartid_map = kcalloc(req_num, sizeof(u32), GFP_KERNEL);
+ if (!reqpartid_map)
+ return -ENOMEM;
+
+ for (idx = 0; idx < req_num; idx++)
+ reqpartid_map[idx] = idx;
+
+ return 0;
+}
+
+static void reqpartid_exit(void)
+{
+ kfree(reqpartid_map);
+}
+
+static void update_rmid_entries_for_reqpartid(u32 reqpartid)
+{
+ int pmg;
+ u32 intpartid = reqpartid_map[reqpartid];
+ u32 closid = partid2closid(intpartid);
+
+ for (pmg = 0; pmg <= mpam_pmg_max; pmg++)
+ rmid_entry_reassign_closid(closid, req_pmg2rmid(reqpartid, pmg));
+}
+
+int resctrl_arch_rmid_expand(u32 closid)
+{
+ int i;
+
+ for (i = resctrl_arch_get_num_closid(NULL);
+ i < get_num_reqpartid(); i++) {
+
+ /* Here means the reqpartid 'i' is free. */
+ if (reqpartid_map[i] >= resctrl_arch_get_num_closid(NULL)) {
+ if (cdp_enabled) {
+ reqpartid_map[i] = resctrl_get_config_index(closid, CDP_DATA);
+ /*
+ * Reqpartids are always allocated in
+ * pairs, never out-of-bounds access.
+ */
+ reqpartid_map[i + 1] = resctrl_get_config_index(closid, CDP_CODE);
+ } else {
+ reqpartid_map[i] = resctrl_get_config_index(closid, CDP_NONE);
+ }
+ update_rmid_entries_for_reqpartid(i);
+ return i;
+ }
+ }
+
+ return -ENOSPC;
+}
+
+void resctrl_arch_rmid_reclaim(u32 closid, u32 rmid)
+{
+ int pmg;
+ u32 intpartid;
+ int reqpartid = rmid2reqpartid(rmid);
+
+ if (reqpartid < resctrl_arch_get_num_closid(NULL))
+ return;
+
+ if (cdp_enabled)
+ intpartid = resctrl_get_config_index(closid, CDP_DATA);
+ else
+ intpartid = resctrl_get_config_index(closid, CDP_NONE);
+
+ WARN_ON_ONCE(intpartid != req2intpartid(reqpartid));
+
+ for (pmg = 0; pmg <= mpam_pmg_max; pmg++) {
+ if (rmid_is_occupied(closid, req_pmg2rmid(reqpartid, pmg)))
+ break;
+ }
+
+ if (pmg > mpam_pmg_max) {
+ reqpartid_map[reqpartid] = reqpartid;
+ if (cdp_enabled)
+ reqpartid_map[reqpartid + 1] = reqpartid + 1;
+
+ update_rmid_entries_for_reqpartid(reqpartid);
+ }
+}
+
int mpam_resctrl_setup(void)
{
int err = 0;
@@ -1720,10 +1830,16 @@ int mpam_resctrl_setup(void)
return -EOPNOTSUPP;
}

- err = resctrl_init();
+ err = reqpartid_init();
if (err)
return err;

+ err = resctrl_init();
+ if (err) {
+ reqpartid_exit();
+ return err;
+ }
+
WRITE_ONCE(resctrl_enabled, true);

return 0;
@@ -1741,6 +1857,7 @@ void mpam_resctrl_exit(void)

WRITE_ONCE(resctrl_enabled, false);
resctrl_exit();
+ reqpartid_exit();
}

/*
diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index f92a36187a52..d45422965907 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h
@@ -59,6 +59,23 @@ void resctrl_arch_set_cpu_default_closid_rmid(int cpu, u32 closid, u32 rmid);
void resctrl_arch_sched_in(struct task_struct *tsk);
bool resctrl_arch_match_closid(struct task_struct *tsk, u32 closid);
bool resctrl_arch_match_rmid(struct task_struct *tsk, u32 closid, u32 rmid);
+
+/**
+ * resctrl_arch_rmid_expand() - Expand the RMID resources for the specified closid.
+ * @closid: closid that matches the rmid.
+ *
+ * Return:
+ * 0 on success, or -ENOSPC etc on error.
+ */
+int resctrl_arch_rmid_expand(u32 closid);
+
+/**
+ * resctrl_arch_rmid_reclaim() - Reclaim the rmid resources for the specified closid.
+ * @closid: closid that matches the rmid.
+ * @rmid: Reclaim the rmid specified.
+ */
+void resctrl_arch_rmid_reclaim(u32 closid, u32 rmid);
+
u32 resctrl_arch_rmid_idx_encode(u32 closid, u32 rmid);
void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid);
u32 resctrl_arch_system_num_rmid_idx(void);
--
2.25.1