[PATCH v8 next 02/10] arm_mpam: Add intPARTID and reqPARTID support for Narrow-PARTID feature

Zeng Heng
2026-04-13T08:55:34Z

Introduce Narrow-PARTID (partid_nrw) feature support, which enables
many-to-one mapping of request PARTIDs (reqPARTID) to internal PARTIDs
(intPARTID). This expands monitoring capability by allowing a single
control group to track more task types through multiple reqPARTIDs
per intPARTID, bypassing the PMG limit in some extent.

intPARTID: Internal PARTID used for control group configuration.
Configurations are synchronized to all reqPARTIDs mapped to the same
intPARTID. Count is indicated by MPAMF_PARTID_NRW_IDR.INTPARTID_MAX, or
defaults to PARTID count if Narrow-PARTID is unsupported.

reqPARTID: Request PARTID used to expand monitoring groups. Enables
a single control group to monitor more task types by multiple reqPARTIDs
within one intPARTID, overcoming the PMG count limitation.

For systems with homogeneous MSCs (all supporting Narrow-PARTID), the
driver exposes the full reqPARTID range directly. For heterogeneous
systems where some MSCs lack Narrow-PARTID support, the driver utilizes
PARTIDs beyond the intPARTID range as reqPARTIDs to expand monitoring
capacity.

So, the numbers of control group and monitoring group are calculated as:

n = min(intPARTID, PARTID) /* the number of control groups */
l = min(reqPARTID, PARTID) /* the number of monitoring groups */
m = l // n /* monitoring groups per control group */

Where:

intPARTID: intPARTIDs on Narrow-PARTID-capable MSCs
reqPARTID: reqPARTIDs on Narrow-PARTID-capable MSCs
PARTID: PARTIDs on non-Narrow-PARTID-capable MSCs

Example: L3 cache (256 PARTIDs, without Narrow-PARTID feature) +
MATA (32 intPARTIDs, 256 reqPARTIDs):

n = min( 32, 256) = 32 intPARTIDs
l = min(256, 256) = 256 reqPARTIDs
m = 256 / 32 = 8 reqPARTIDs per intPARTID

Implementation notes:
* Handle mixed MSC systems (some support Narrow-PARTID, some don't) by
taking minimum number of intPARTIDs across all MSCs.
* resctrl_arch_get_num_closid() now returns the number of intPARTIDs
(was PARTID).

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
---
drivers/resctrl/mpam_devices.c | 30 ++++++++++++++++++++----------
drivers/resctrl/mpam_internal.h | 2 ++
drivers/resctrl/mpam_resctrl.c | 4 ++--
3 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 41b14344b16f..cf067bf5092e 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -63,6 +63,7 @@ static DEFINE_MUTEX(mpam_cpuhp_state_lock);
* Generating traffic outside this range will result in screaming interrupts.
*/
u16 mpam_partid_max;
+u16 mpam_intpartid_max;
u8 mpam_pmg_max;
static bool partid_max_init, partid_max_published;
static DEFINE_SPINLOCK(partid_max_lock);
@@ -288,10 +289,12 @@ int mpam_register_requestor(u16 partid_max, u8 pmg_max)
{
guard(spinlock)(&partid_max_lock);
if (!partid_max_init) {
+ mpam_intpartid_max = partid_max;
mpam_partid_max = partid_max;
mpam_pmg_max = pmg_max;
partid_max_init = true;
} else if (!partid_max_published) {
+ mpam_intpartid_max = min(mpam_intpartid_max, partid_max);
mpam_partid_max = min(mpam_partid_max, partid_max);
mpam_pmg_max = min(mpam_pmg_max, pmg_max);
} else {
@@ -931,7 +934,9 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
u16 partid_max = FIELD_GET(MPAMF_PARTID_NRW_IDR_INTPARTID_MAX, nrwidr);

mpam_set_feature(mpam_feat_partid_nrw, props);
- msc->partid_max = min(msc->partid_max, partid_max);
+ msc->intpartid_max = min(msc->partid_max, partid_max);
+ } else {
+ msc->intpartid_max = msc->partid_max;
}
}

@@ -995,6 +1000,7 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)

spin_lock(&partid_max_lock);
mpam_partid_max = min(mpam_partid_max, msc->partid_max);
+ mpam_intpartid_max = min(mpam_intpartid_max, msc->intpartid_max);
mpam_pmg_max = min(mpam_pmg_max, msc->pmg_max);
spin_unlock(&partid_max_lock);

@@ -1711,7 +1717,7 @@ static int mpam_reset_ris(void *arg)
return 0;

spin_lock(&partid_max_lock);
- partid_max = mpam_partid_max;
+ partid_max = mpam_intpartid_max;
spin_unlock(&partid_max_lock);
for (partid = 0; partid <= partid_max; partid++)
mpam_reprogram_ris_partid(ris, partid, &reset_cfg);
@@ -1767,7 +1773,7 @@ static void mpam_reprogram_msc(struct mpam_msc *msc)
struct mpam_write_config_arg arg;

/*
- * No lock for mpam_partid_max as partid_max_published has been
+ * No lock for mpam_intpartid_max as partid_max_published has been
* set by mpam_enabled(), so the values can no longer change.
*/
mpam_assert_partid_sizes_fixed();
@@ -1784,7 +1790,7 @@ static void mpam_reprogram_msc(struct mpam_msc *msc)
arg.comp = ris->vmsc->comp;
arg.ris = ris;
reset = true;
- for (partid = 0; partid <= mpam_partid_max; partid++) {
+ for (partid = 0; partid <= mpam_intpartid_max; partid++) {
cfg = &ris->vmsc->comp->cfg[partid];
if (!bitmap_empty(cfg->features, MPAM_FEATURE_LAST))
reset = false;
@@ -2607,7 +2613,7 @@ static void mpam_reset_component_cfg(struct mpam_component *comp)
if (!comp->cfg)
return;

- for (i = 0; i <= mpam_partid_max; i++) {
+ for (i = 0; i <= mpam_intpartid_max; i++) {
comp->cfg[i] = (struct mpam_config) {};
if (cprops->cpbm_wd)
comp->cfg[i].cpbm = GENMASK(cprops->cpbm_wd - 1, 0);
@@ -2627,7 +2633,7 @@ static int __allocate_component_cfg(struct mpam_component *comp)
if (comp->cfg)
return 0;

- comp->cfg = kzalloc_objs(*comp->cfg, mpam_partid_max + 1);
+ comp->cfg = kzalloc_objs(*comp->cfg, mpam_intpartid_max + 1);
if (!comp->cfg)
return -ENOMEM;

@@ -2694,7 +2700,7 @@ static void mpam_enable_once(void)
int err;

/*
- * Once the cpuhp callbacks have been changed, mpam_partid_max can no
+ * Once the cpuhp callbacks have been changed, mpam_intpartid_max can no
* longer change.
*/
spin_lock(&partid_max_lock);
@@ -2743,9 +2749,13 @@ static void mpam_enable_once(void)
mpam_register_cpuhp_callbacks(mpam_cpu_online, mpam_cpu_offline,
"mpam:online");

- /* Use printk() to avoid the pr_fmt adding the function name. */
- printk(KERN_INFO "MPAM enabled with %u PARTIDs and %u PMGs\n",
- mpam_partid_max + 1, mpam_pmg_max + 1);
+ if (mpam_partid_max == mpam_intpartid_max)
+ /* Use printk() to avoid the pr_fmt adding the function name. */
+ printk(KERN_INFO "MPAM enabled with %u PARTIDs and %u PMGs\n",
+ mpam_partid_max + 1, mpam_pmg_max + 1);
+ else
+ printk(KERN_INFO "MPAM enabled with %u reqPARTIDs, %u intPARTIDs and %u PMGs\n",
+ mpam_partid_max + 1, mpam_intpartid_max + 1, mpam_pmg_max + 1);
}

static void mpam_reset_component_locked(struct mpam_component *comp)
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 1914aefdcba9..790a90a5ccd9 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -81,6 +81,7 @@ struct mpam_msc {
*/
struct mutex probe_lock;
bool probed;
+ u16 intpartid_max;
u16 partid_max;
u8 pmg_max;
unsigned long ris_idxs;
@@ -452,6 +453,7 @@ extern struct list_head mpam_classes;

/* System wide partid/pmg values */
extern u16 mpam_partid_max;
+extern u16 mpam_intpartid_max;
extern u8 mpam_pmg_max;

/* Scheduled work callback to enable mpam once all MSC have been probed */
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 161fb8905e28..5f4364c8101a 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -223,7 +223,7 @@ int resctrl_arch_set_cdp_enabled(enum resctrl_res_level rid, bool enable)
mpam_resctrl_controls[RDT_RESOURCE_MBA].resctrl_res.alloc_capable = false;

if (enable) {
- if (mpam_partid_max < 1)
+ if (mpam_intpartid_max < 1)
return -EINVAL;

partid_d = resctrl_get_config_index(RESCTRL_RESERVED_CLOSID, CDP_DATA);
@@ -254,7 +254,7 @@ static bool mpam_resctrl_hide_cdp(enum resctrl_res_level rid)
*/
u32 resctrl_arch_get_num_closid(struct rdt_resource *ignored)
{
- return mpam_partid_max + 1;
+ return mpam_intpartid_max + 1;
}

u32 resctrl_arch_system_num_rmid_idx(void)
--
2.25.1