[PATCH v5 0/5] arm_mpam: resctrl: Counter Assignment (ABMC)

[PATCH v5 0/5] arm_mpam: resctrl: Counter Assignment (ABMC)

[Ben Horgan]

Version 5 of this series addresses a few review comments but is pretty
similar to v4. The precursors in x86/cache have been merged so there is no
longer a need for this to go through there. It's likely easiest if this
goes through arm64.

This series adds support for memory bandwidth monitoring. Counter assignment
will be used for all platforms with memory bandwidth monitors rather than just
those with insufficient counters as originally proposed.

rfc v1: https://lore.kernel.org/lkml/20260225205436.3571756-1-ben.horgan@arm.com/
rfc v2: https://lore.kernel.org/lkml/20260319165540.381410-1-ben.horgan@arm.com/
v3: https://lore.kernel.org/linux-arm-kernel/20260511154147.557481-1-ben.horgan@arm.com/
v4: https://lore.kernel.org/lkml/20260520212458.1797221-1-ben.horgan@arm.com/

The code can be found at:
https://gitlab.arm.com/linux-arm/linux-bh.git mpam_abmc_v5

Ben Horgan (2):
  arm_mpam: resctrl: Pre-allocate assignable monitors
  arm64: mpam: Add memory bandwidth usage (MBWU) documentation

James Morse (3):
  arm_mpam: resctrl: Pick classes for use as MBM counters
  arm_mpam: resctrl: Add resctrl_arch_config_cntr() for ABMC use
  arm_mpam: resctrl: Add resctrl_arch_cntr_read() &
    resctrl_arch_reset_cntr()

 Documentation/arch/arm64/mpam.rst |  22 +++
 drivers/resctrl/mpam_internal.h   |   6 +-
 drivers/resctrl/mpam_resctrl.c    | 318 +++++++++++++++++++++++++++---
 3 files changed, 323 insertions(+), 23 deletions(-)

-- 
2.43.0

[PATCH v5 1/5] arm_mpam: resctrl: Pick classes for use as MBM counters

[Ben Horgan]

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

resctrl has two types of bandwidth counters, NUMA-local and global. MPAM
can only count globally; either using MSC at the L3 cache or in the memory
controllers. When global and local equate to the same thing continue just
to call it global.

Pick the corresponding MPAM classes to back the MBM counters. As resctrl
requires all monitors to be at the L3 cache, we can only use the counters
at the memory controllers when they have the same topology as the L3 cache
and the traffic they see if the same. In particular, for the bandwidth
counters at the memory controllers to be exposed to resctrl it is required
there is a single L3 cache and a single NUMA node as otherwise cross NUMA
traffic will be counted at the wrong instance.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Zeng Heng <zengheng4@huawei.com>
Tested-by: Fenghua Yu <fenghuay@nvidia.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
---
Changes since rfc v1:
Move finding any_mon_comp into monitor boilerplate patch
Move mpam_resctrl_get_domain_from_cpu() into monitor boilerplate
Remove free running check
Trim commit message

Changes since v3:
Extra paragraph in commit message

Changes since v4:
Commit message tag ordering
New sentence in block comment (Fenghua)
---
 drivers/resctrl/mpam_resctrl.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 226ff6f532fa..0fce9703b869 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -606,6 +606,16 @@ static bool cache_has_usable_csu(struct mpam_class *class)
 	return true;
 }
 
+static bool class_has_usable_mbwu(struct mpam_class *class)
+{
+	struct mpam_props *cprops = &class->props;
+
+	if (!mpam_has_feature(mpam_feat_msmon_mbwu, cprops))
+		return false;
+
+	return true;
+}
+
 /*
  * Calculate the worst-case percentage change from each implemented step
  * in the control.
@@ -983,6 +993,24 @@ static void mpam_resctrl_pick_counters(void)
 				break;
 			}
 		}
+
+		if (class_has_usable_mbwu(class) &&
+		    topology_matches_l3(class) &&
+		    traffic_matches_l3(class)) {
+			pr_debug("class %u has usable MBWU, and matches L3 topology and traffic\n",
+				 class->level);
+
+			/*
+			 * An MSC measures bandwidth for a path determined by
+			 * its location in hardware. We can't distinguish
+			 * traffic by destination so we don't know if it's
+			 * staying on the same NUMA node. Hence, we can't
+			 * calculate mbm_local except when we only have one L3
+			 * and it's equivalent to mbm_total and so always use
+			 * mbm_total.
+			 */
+			counter_update_class(QOS_L3_MBM_TOTAL_EVENT_ID, class);
+		}
 	}
 }
 
-- 
2.43.0

[PATCH v5 2/5] arm_mpam: resctrl: Pre-allocate assignable monitors

[Ben Horgan]

MPAM is able to emulate ABMC, i.e. mbm_event mode, by making memory
bandwidth monitors assignable. Rather than supporting the 'default'
mbm_assign_mode always use 'mbm_event' mode even if there are sufficient
memory bandwidth monitors. The per monitor event configuration is only
provided by resctrl when in 'mbm_event' mode and so only allowing
'mbm_event' mode will make it easier to support per-monitor event
configuration for MPAM. For the moment, the only event supported is
mbm_total_event with no bandwidth type configuration. The 'mbm_assign_mode'
file will still show 'default' when there is no support for memory
bandwidth monitoring.

The monitors need to be allocated from the driver, and mapped to whichever
control/monitor group resctrl wants to use them with.

Add a second array to hold the monitor values indexed by resctrl's cntr_id.

When CDP is in use, two monitors are needed so the available number of
counters halves. Platforms with one monitor will have zero monitors when
CDP is in use.

Co-developed-by: James Morse <james.morse@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Fenghua Yu <fenghuay@nvidia.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
---
Changes since rfc v1:
abmc enabled even if enough counters
Helpers from dropped free running commits
carry on with zero counters if using cdp
set config bits
use kmalloc_objs
drop tags for rework
Configure mbm_cntr_configurable, mbm_cntr_assign_fixed

Changes since rfc v2:
Don't set mon->assigned_counters to an error pointer
Fix mpam_resctrl_teardown_mon()
Remove free running check
Separate cleanup allocations, e.g. __free(), from the rest
Restrict scope on err in mpam_resctrl_monitor_init()

Changes since v3:
Correct NULL check in mpam_resctrl_teardown_mon() (Shaopeng)
variable allocation ordering in mpam_resctrl_pick_domain_id() (Shaopeng)
Move mon.* assignments from mpam_resctrl_monitor_sync_abmc_vals()
to mpam_resctrl_monitor_init_abmc() counters (Sashiko)
use kvmalloc_obj() for allocations that may be big on some
platforms (Sashiko)

Changes since v4:
Remove l3_num_allocated_mbwu (Koba)
indexed by idx -> indexed by resctrl's cntr_id (Fenghua)
---
 drivers/resctrl/mpam_internal.h |   6 +-
 drivers/resctrl/mpam_resctrl.c  | 143 +++++++++++++++++++++++++++++++-
 2 files changed, 145 insertions(+), 4 deletions(-)

diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 04d1a59f02af..def0e3a65c23 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -409,7 +409,11 @@ struct mpam_resctrl_res {
 struct mpam_resctrl_mon {
 	struct mpam_class	*class;
 
-	/* per-class data that resctrl needs will live here */
+	/* Array of allocated MBWU monitors, indexed by (closid, rmid). */
+	int			*mbwu_idx_to_mon;
+
+	/* Array of assigned MBWU monitors, indexed by resctrl's cntr_id. */
+	int			*assigned_counters;
 };
 
 static inline int mpam_alloc_csu_mon(struct mpam_class *class)
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 0fce9703b869..91b589b110a2 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -140,7 +140,7 @@ int resctrl_arch_cntr_read(struct rdt_resource *r, struct rdt_l3_mon_domain *d,
 
 bool resctrl_arch_mbm_cntr_assign_enabled(struct rdt_resource *r)
 {
-	return false;
+	return (r == &mpam_resctrl_controls[RDT_RESOURCE_L3].resctrl_res);
 }
 
 int resctrl_arch_mbm_cntr_assign_set(struct rdt_resource *r, bool enable)
@@ -185,6 +185,26 @@ static void resctrl_reset_task_closids(void)
 	read_unlock(&tasklist_lock);
 }
 
+static void mpam_resctrl_monitor_sync_abmc_vals(struct rdt_resource *l3)
+{
+	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[QOS_L3_MBM_TOTAL_EVENT_ID];
+
+	if (!mon->class)
+		return;
+
+	if (!mon->assigned_counters)
+		return;
+
+	l3->mon.num_mbm_cntrs = mon->class->props.num_mbwu_mon;
+	if (cdp_enabled)
+		l3->mon.num_mbm_cntrs /= 2;
+
+	/*
+	 * Continue as normal even if enabling cdp causes there to be
+	 * zero counters. This avoids giving resctrl mixed messages.
+	 */
+}
+
 int resctrl_arch_set_cdp_enabled(enum resctrl_res_level rid, bool enable)
 {
 	u32 partid_i = RESCTRL_RESERVED_CLOSID, partid_d = RESCTRL_RESERVED_CLOSID;
@@ -244,6 +264,7 @@ int resctrl_arch_set_cdp_enabled(enum resctrl_res_level rid, bool enable)
 	WRITE_ONCE(arm64_mpam_global_default, mpam_get_regval(current));
 
 	resctrl_reset_task_closids();
+	mpam_resctrl_monitor_sync_abmc_vals(l3);
 
 	for_each_possible_cpu(cpu)
 		mpam_set_cpu_defaults(cpu, partid_d, partid_i, 0, 0);
@@ -613,6 +634,9 @@ static bool class_has_usable_mbwu(struct mpam_class *class)
 	if (!mpam_has_feature(mpam_feat_msmon_mbwu, cprops))
 		return false;
 
+	if (!cprops->num_mbwu_mon)
+		return false;
+
 	return true;
 }
 
@@ -935,6 +959,50 @@ static void mpam_resctrl_pick_mba(void)
 	}
 }
 
+static void __free_mbwu_mon(struct mpam_class *class, int *array,
+			    u16 num_mbwu_mon)
+{
+	for (int i = 0; i < num_mbwu_mon; i++) {
+		if (array[i] < 0)
+			continue;
+
+		mpam_free_mbwu_mon(class, array[i]);
+		array[i] = ~0;
+	}
+}
+
+static int __alloc_mbwu_mon(struct mpam_class *class, int *array,
+			    u16 num_mbwu_mon)
+{
+	for (int i = 0; i < num_mbwu_mon; i++) {
+		int mbwu_mon = mpam_alloc_mbwu_mon(class);
+
+		if (mbwu_mon < 0) {
+			__free_mbwu_mon(class, array, num_mbwu_mon);
+			return mbwu_mon;
+		}
+		array[i] = mbwu_mon;
+	}
+
+	return 0;
+}
+
+static int *__alloc_mbwu_array(struct mpam_class *class, u16 num_mbwu_mon)
+{
+	int err;
+
+	int *array __free(kvfree) = kvmalloc_objs(*array, num_mbwu_mon);
+	if (!array)
+		return ERR_PTR(-ENOMEM);
+
+	memset(array, -1, num_mbwu_mon * sizeof(*array));
+
+	err = __alloc_mbwu_mon(class, array, num_mbwu_mon);
+	if (err)
+		return ERR_PTR(err);
+	return_ptr(array);
+}
+
 static void counter_update_class(enum resctrl_event_id evt_id,
 				 struct mpam_class *class)
 {
@@ -1091,6 +1159,43 @@ static int mpam_resctrl_pick_domain_id(int cpu, struct mpam_component *comp)
 	return comp->comp_id;
 }
 
+/*
+ * This must run after all event counters have been picked so that any free
+ * running counters have already been allocated.
+ */
+static int mpam_resctrl_monitor_init_abmc(struct mpam_resctrl_mon *mon)
+{
+	struct mpam_resctrl_res *res = &mpam_resctrl_controls[RDT_RESOURCE_L3];
+	size_t num_rmid = resctrl_arch_system_num_rmid_idx();
+	struct rdt_resource *l3 = &res->resctrl_res;
+	struct mpam_class *class = mon->class;
+	u16 num_mbwu_mon;
+	int *cntrs;
+
+	int *rmid_array __free(kvfree) = kvmalloc_objs(*rmid_array, num_rmid);
+	if (!rmid_array) {
+		pr_debug("Failed to allocate RMID array\n");
+		return -ENOMEM;
+	}
+	memset(rmid_array, -1, num_rmid * sizeof(*rmid_array));
+
+	num_mbwu_mon = class->props.num_mbwu_mon;
+	cntrs = __alloc_mbwu_array(mon->class, num_mbwu_mon);
+	if (IS_ERR(cntrs))
+		return PTR_ERR(cntrs);
+	mon->assigned_counters = cntrs;
+	mon->mbwu_idx_to_mon = no_free_ptr(rmid_array);
+
+	l3->mon.mbm_cntr_assignable = true;
+	l3->mon.mbm_assign_on_mkdir = true;
+	l3->mon.mbm_cntr_configurable = false;
+	l3->mon.mbm_cntr_assign_fixed = true;
+
+	mpam_resctrl_monitor_sync_abmc_vals(l3);
+
+	return 0;
+}
+
 static int mpam_resctrl_monitor_init(struct mpam_resctrl_mon *mon,
 				     enum resctrl_event_id type)
 {
@@ -1135,8 +1240,21 @@ static int mpam_resctrl_monitor_init(struct mpam_resctrl_mon *mon,
 	 */
 	l3->mon.num_rmid = resctrl_arch_system_num_rmid_idx();
 
-	if (resctrl_enable_mon_event(type, false, 0, NULL))
-		l3->mon_capable = true;
+	if (type == QOS_L3_MBM_TOTAL_EVENT_ID) {
+		int err;
+
+		err = mpam_resctrl_monitor_init_abmc(mon);
+		if (err)
+			return err;
+
+		static_assert(MAX_EVT_CONFIG_BITS == 0x7f);
+		l3->mon.mbm_cfg_mask = MAX_EVT_CONFIG_BITS;
+	}
+
+	if (!resctrl_enable_mon_event(type, false, 0, NULL))
+		return -EINVAL;
+
+	l3->mon_capable = true;
 
 	return 0;
 }
@@ -1699,6 +1817,23 @@ void mpam_resctrl_exit(void)
 	resctrl_exit();
 }
 
+static void mpam_resctrl_teardown_mon(struct mpam_resctrl_mon *mon, struct mpam_class *class)
+{
+	u32 num_mbwu_mon = class->props.num_mbwu_mon;
+
+	if (!mon->mbwu_idx_to_mon)
+		return;
+
+	if (mon->assigned_counters) {
+		__free_mbwu_mon(class, mon->assigned_counters, num_mbwu_mon);
+		kvfree(mon->assigned_counters);
+		mon->assigned_counters = NULL;
+	}
+
+	kvfree(mon->mbwu_idx_to_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().
@@ -1721,6 +1856,8 @@ void mpam_resctrl_teardown_class(struct mpam_class *class)
 	for_each_mpam_resctrl_mon(mon, eventid) {
 		if (mon->class == class) {
 			mon->class = NULL;
+
+			mpam_resctrl_teardown_mon(mon, class);
 			break;
 		}
 	}
-- 
2.43.0

[PATCH v5 3/5] arm_mpam: resctrl: Add resctrl_arch_config_cntr() for ABMC use

[Ben Horgan]

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

ABMC, mbm_event mode, has a helper resctrl_arch_config_cntr() for changing
the mapping between 'cntr_id' and a CLOSID/RMID pair.

Add the helper.

For MPAM this is done by updating the mon->mbwu_idx_to_mon[] array, and as
usual CDP means it needs doing in three different ways.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Fenghua Yu <fenghuay@nvidia.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
---
Changes since new rfc:
Mention mbm_event mode in commit message

Changes since v3:
Warning bound (Sashiko)

Changes since v4:
resctrl_arch_reset_rmid() -> reset_arch_reset_cntr()
---
 drivers/resctrl/mpam_resctrl.c | 48 +++++++++++++++++++++++++++++-----
 1 file changed, 42 insertions(+), 6 deletions(-)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 91b589b110a2..29a8cf8092e0 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -125,12 +125,6 @@ void resctrl_arch_reset_cntr(struct rdt_resource *r, struct rdt_l3_mon_domain *d
 {
 }
 
-void resctrl_arch_config_cntr(struct rdt_resource *r, struct rdt_l3_mon_domain *d,
-			      enum resctrl_event_id evtid, u32 rmid, u32 closid,
-			      u32 cntr_id, bool assign)
-{
-}
-
 int resctrl_arch_cntr_read(struct rdt_resource *r, struct rdt_l3_mon_domain *d,
 			   u32 unused, u32 rmid, int cntr_id,
 			   enum resctrl_event_id eventid, u64 *val)
@@ -1082,6 +1076,48 @@ static void mpam_resctrl_pick_counters(void)
 	}
 }
 
+static void __config_cntr(struct mpam_resctrl_mon *mon, u32 cntr_id,
+			  enum resctrl_conf_type cdp_type, u32 closid, u32 rmid,
+			  bool assign)
+{
+	/* Same CDP index remap as closid; maps cntr_id to assigned_counters[]. */
+	u32 mbwu_idx, mon_idx = resctrl_get_config_index(cntr_id, cdp_type);
+
+	closid = resctrl_get_config_index(closid, cdp_type);
+	mbwu_idx = resctrl_arch_rmid_idx_encode(closid, rmid);
+
+	if (assign)
+		mon->mbwu_idx_to_mon[mbwu_idx] = mon->assigned_counters[mon_idx];
+	else
+		mon->mbwu_idx_to_mon[mbwu_idx] = -1;
+}
+
+void resctrl_arch_config_cntr(struct rdt_resource *r, struct rdt_l3_mon_domain *d,
+			      enum resctrl_event_id evtid, u32 rmid, u32 closid,
+			      u32 cntr_id, bool assign)
+{
+	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[evtid];
+
+	if (evtid != QOS_L3_MBM_TOTAL_EVENT_ID) {
+		pr_debug("unexpected event id\n");
+		return;
+	}
+
+	if (!mon->mbwu_idx_to_mon || !mon->assigned_counters) {
+		pr_debug("monitor arrays not allocated\n");
+		return;
+	}
+
+	if (cdp_enabled) {
+		__config_cntr(mon, cntr_id, CDP_CODE, closid, rmid, assign);
+		__config_cntr(mon, cntr_id, CDP_DATA, closid, rmid, assign);
+	} else {
+		__config_cntr(mon, cntr_id, CDP_NONE, closid, rmid, assign);
+	}
+
+	resctrl_arch_reset_cntr(r, d, closid, rmid, cntr_id, QOS_L3_MBM_TOTAL_EVENT_ID);
+}
+
 static int mpam_resctrl_control_init(struct mpam_resctrl_res *res)
 {
 	struct mpam_class *class = res->class;
-- 
2.43.0

[PATCH v5 4/5] arm_mpam: resctrl: Add resctrl_arch_cntr_read() & resctrl_arch_reset_cntr()

[Ben Horgan]

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

When used in 'mbm_event' mode, ABMC emulation, resctrl uses arch hooks to
read and reset the memory bandwidth utilization (MBWU) counters.

Add these.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Fenghua Yu <fenghuay@nvidia.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
---
Changes since rfc v1:
Move __reset_mon() and reset_mon_cdp_safe() helpers here
support mbwu in __read_mon()
Mention mbm_event mode in commit message

Changes since v3:
USE_PREALLOCATED_IDX, separate h/w counters are needed for code and data
when cdp_enabled is true
---
 drivers/resctrl/mpam_resctrl.c | 99 +++++++++++++++++++++++++++++-----
 1 file changed, 86 insertions(+), 13 deletions(-)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 29a8cf8092e0..7769c16bf319 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -119,19 +119,6 @@ void resctrl_arch_reset_rmid(struct rdt_resource *r, struct rdt_l3_mon_domain *d
 {
 }
 
-void resctrl_arch_reset_cntr(struct rdt_resource *r, struct rdt_l3_mon_domain *d,
-			     u32 closid, u32 rmid, int cntr_id,
-			     enum resctrl_event_id eventid)
-{
-}
-
-int resctrl_arch_cntr_read(struct rdt_resource *r, struct rdt_l3_mon_domain *d,
-			   u32 unused, u32 rmid, int cntr_id,
-			   enum resctrl_event_id eventid, u64 *val)
-{
-	return -EOPNOTSUPP;
-}
-
 bool resctrl_arch_mbm_cntr_assign_enabled(struct rdt_resource *r)
 {
 	return (r == &mpam_resctrl_controls[RDT_RESOURCE_L3].resctrl_res);
@@ -469,6 +456,14 @@ static int __read_mon(struct mpam_resctrl_mon *mon, struct mpam_component *mon_c
 	/* Shift closid to account for CDP */
 	closid = resctrl_get_config_index(closid, cdp_type);
 
+	if (mon_idx == USE_PRE_ALLOCATED) {
+		int mbwu_idx = resctrl_arch_rmid_idx_encode(closid, rmid);
+
+		mon_idx = mon->mbwu_idx_to_mon[mbwu_idx];
+		if (mon_idx == -1)
+			return -ENOENT;
+	}
+
 	if (irqs_disabled()) {
 		/* Check if we can access this domain without an IPI */
 		return -EIO;
@@ -541,6 +536,84 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain_hdr *hdr,
 				 closid, rmid, val);
 }
 
+/* MBWU counters when in ABMC mode */
+int resctrl_arch_cntr_read(struct rdt_resource *r, struct rdt_l3_mon_domain *d,
+			   u32 closid, u32 rmid, int mon_idx,
+			   enum resctrl_event_id eventid, u64 *val)
+{
+	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[eventid];
+	struct mpam_resctrl_dom *l3_dom;
+	struct mpam_component *mon_comp;
+
+	if (!mpam_is_enabled())
+		return -EINVAL;
+
+	if (eventid == QOS_L3_OCCUP_EVENT_ID || !mon->class)
+		return -EINVAL;
+
+	l3_dom = container_of(d, struct mpam_resctrl_dom, resctrl_mon_dom);
+	mon_comp = l3_dom->mon_comp[eventid];
+
+	return read_mon_cdp_safe(mon, mon_comp, mpam_feat_msmon_mbwu,
+				 USE_PRE_ALLOCATED, closid, rmid, val);
+}
+
+static void __reset_mon(struct mpam_resctrl_mon *mon, struct mpam_component *mon_comp,
+			int mon_idx,
+			enum resctrl_conf_type cdp_type, u32 closid, u32 rmid)
+{
+	struct mon_cfg cfg = { };
+
+	if (!mpam_is_enabled())
+		return;
+
+	/* Shift closid to account for CDP */
+	closid = resctrl_get_config_index(closid, cdp_type);
+
+	if (mon_idx == USE_PRE_ALLOCATED) {
+		int mbwu_idx = resctrl_arch_rmid_idx_encode(closid, rmid);
+
+		mon_idx = mon->mbwu_idx_to_mon[mbwu_idx];
+	}
+
+	if (mon_idx == -1)
+		return;
+	cfg.mon = mon_idx;
+	mpam_msmon_reset_mbwu(mon_comp, &cfg);
+}
+
+static void reset_mon_cdp_safe(struct mpam_resctrl_mon *mon, struct mpam_component *mon_comp,
+			       int mon_idx, u32 closid, u32 rmid)
+{
+	if (cdp_enabled) {
+		__reset_mon(mon, mon_comp, mon_idx, CDP_CODE, closid, rmid);
+		__reset_mon(mon, mon_comp, mon_idx, CDP_DATA, closid, rmid);
+	} else {
+		__reset_mon(mon, mon_comp, mon_idx, CDP_NONE, closid, rmid);
+	}
+}
+
+/* Reset an assigned counter */
+void resctrl_arch_reset_cntr(struct rdt_resource *r, struct rdt_l3_mon_domain *d,
+			     u32 closid, u32 rmid, int cntr_id,
+			     enum resctrl_event_id eventid)
+{
+	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[eventid];
+	struct mpam_resctrl_dom *l3_dom;
+	struct mpam_component *mon_comp;
+
+	if (!mpam_is_enabled())
+		return;
+
+	if (eventid == QOS_L3_OCCUP_EVENT_ID || !mon->class)
+		return;
+
+	l3_dom = container_of(d, struct mpam_resctrl_dom, resctrl_mon_dom);
+	mon_comp = l3_dom->mon_comp[eventid];
+
+	reset_mon_cdp_safe(mon, mon_comp, USE_PRE_ALLOCATED, closid, rmid);
+}
+
 /*
  * The rmid realloc threshold should be for the smallest cache exposed to
  * resctrl.
-- 
2.43.0

[PATCH v5 5/5] arm64: mpam: Add memory bandwidth usage (MBWU) documentation

[Ben Horgan]

Memory bandwidth monitoring make uses of MBWU monitors and is now exposed
to the user via resctrl. Add some documentation so the user knows what to
expect.

Co-developed-by: James Morse <james.morse@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
---
Changes since v4:
Add paragraph about the future.
---
 Documentation/arch/arm64/mpam.rst | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/Documentation/arch/arm64/mpam.rst b/Documentation/arch/arm64/mpam.rst
index 570f51a8d4eb..67fe515ed501 100644
--- a/Documentation/arch/arm64/mpam.rst
+++ b/Documentation/arch/arm64/mpam.rst
@@ -65,6 +65,28 @@ The supported features are:
   there is at least one CSU monitor on each MSC that makes up the L3 group.
   Exposing CSU counters from other caches or devices is not supported.
 
+* Memory Bandwidth Usage (MBWU) on or after the L3 cache.  resctrl uses the
+  L3 cache-id to identify where the memory bandwidth is measured. For this
+  reason the platform must have an L3 cache with cache-id's supplied by
+  firmware. (The platform doesn't need to support MPAM.)
+
+  Memory bandwidth monitoring makes use of MBWU monitors in each MSC that
+  makes up the L3 group. If the memory bandwidth monitoring is on the memory
+  rather than the L3 then there must be a single global L3 as otherwise it
+  is unknown which L3 the traffic came from.
+
+  To expose 'mbm_total_bytes', the topology of the group of MSC chosen must
+  match the topology of the L3 cache so that the cache-id's can be
+  repainted. For example: Platforms with Memory bandwidth monitors on
+  CPU-less NUMA nodes cannot expose 'mbm_total_bytes' as these nodes do not
+  have a corresponding L3 cache. 'mbm_local_bytes' is not exposed as MPAM
+  cannot distinguish local traffic from global traffic.
+
+  All these restrictions based on L3 cache are due to resctrl, currently, only
+  supporting monitoring at the L3 scope. It is expected that going forward more
+  MBWU monitors can be exposed to the user after support for more monitoring
+  scopes is added to resctrl.
+
 Reporting Bugs
 ==============
 If you are not seeing the counters or controls you expect please share the
-- 
2.43.0

Re: [PATCH v5 5/5] arm64: mpam: Add memory bandwidth usage (MBWU) documentation

[Fenghua Yu]

On 7/7/26 09:24, Ben Horgan wrote:
> Memory bandwidth monitoring make uses of MBWU monitors and is now exposed
> to the user via resctrl. Add some documentation so the user knows what to
> expect.
> 
> Co-developed-by: James Morse <james.morse@arm.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>

Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>

Thanks.

-Fenghua
> ---
> Changes since v4:
> Add paragraph about the future.
> ---
>   Documentation/arch/arm64/mpam.rst | 22 ++++++++++++++++++++++
>   1 file changed, 22 insertions(+)
> 
> diff --git a/Documentation/arch/arm64/mpam.rst b/Documentation/arch/arm64/mpam.rst
> index 570f51a8d4eb..67fe515ed501 100644
> --- a/Documentation/arch/arm64/mpam.rst
> +++ b/Documentation/arch/arm64/mpam.rst
> @@ -65,6 +65,28 @@ The supported features are:
>     there is at least one CSU monitor on each MSC that makes up the L3 group.
>     Exposing CSU counters from other caches or devices is not supported.
>   
> +* Memory Bandwidth Usage (MBWU) on or after the L3 cache.  resctrl uses the
> +  L3 cache-id to identify where the memory bandwidth is measured. For this
> +  reason the platform must have an L3 cache with cache-id's supplied by
> +  firmware. (The platform doesn't need to support MPAM.)
> +
> +  Memory bandwidth monitoring makes use of MBWU monitors in each MSC that
> +  makes up the L3 group. If the memory bandwidth monitoring is on the memory
> +  rather than the L3 then there must be a single global L3 as otherwise it
> +  is unknown which L3 the traffic came from.
> +
> +  To expose 'mbm_total_bytes', the topology of the group of MSC chosen must
> +  match the topology of the L3 cache so that the cache-id's can be
> +  repainted. For example: Platforms with Memory bandwidth monitors on
> +  CPU-less NUMA nodes cannot expose 'mbm_total_bytes' as these nodes do not
> +  have a corresponding L3 cache. 'mbm_local_bytes' is not exposed as MPAM
> +  cannot distinguish local traffic from global traffic.
> +
> +  All these restrictions based on L3 cache are due to resctrl, currently, only
> +  supporting monitoring at the L3 scope. It is expected that going forward more
> +  MBWU monitors can be exposed to the user after support for more monitoring
> +  scopes is added to resctrl.
> +
>   Reporting Bugs
>   ==============
>   If you are not seeing the counters or controls you expect please share the