[PATCH RFC v2 11/19] arm_mpam: Emulate MB control with node-scoped MB_NODE control
Fenghua Yu
fenghuay at nvidia.com
Mon Aug 31 10:22:37 PDT 2026
On memory-class MSCs the MB bandwidth control is node-scoped. Add a
node-scoped MB_NODE control that emulates the default MB control by
adding it to the default control's resctrl_ctrl::emulated_by list, so
the legacy "MB:" schemata line keeps working while user space can switch
the resource to native mode to drive MB_NODE directly.
Introduce mpam_resctrl_ctrl_node() to identify memory-class resources
and use it when selecting the control scope, replacing the open-coded
assumption that MBA is always cache-scoped. A memory class has one
component per memory controller, so its control domains are node-scoped
and rdt_resource::ctrl_scope becomes RESCTRL_NODE.
An emulating control has its own control domains, so give the MPAM CPU
hotplug and domain update paths a walk of the emulated_by list.
resctrl_arch_get_config() and resctrl_arch_update_one() accept the
MB_NODE control name alongside the default one, both being backed by the
same MPAM bandwidth partitioning hardware.
Signed-off-by: Fenghua Yu <fenghuay at nvidia.com>
---
drivers/resctrl/mpam_resctrl.c | 265 ++++++++++++++++++++++++++-------
fs/resctrl/ctrlmondata.c | 1 +
include/linux/resctrl.h | 2 +
3 files changed, 211 insertions(+), 57 deletions(-)
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 9a02bc0e091d..cd9bebf5f0c2 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -1264,20 +1264,108 @@ void resctrl_arch_config_cntr(struct rdt_resource *r, struct rdt_l3_mon_domain *
resctrl_arch_reset_cntr(r, d, closid, rmid, cntr_id, evtid);
}
+/*
+ * Bandwidth control on a memory-class MSC is node-scoped, unlike the
+ * cache-scoped control provided by an MSC in front of the L3.
+ */
+static bool mpam_resctrl_ctrl_node(struct rdt_resource *r)
+{
+ struct mpam_resctrl_res *res;
+
+ res = container_of(r, struct mpam_resctrl_res, resctrl_res);
+
+ return mpam_class_memory(res->class);
+}
+
+static bool mpam_resctrl_cache_has_mba(void)
+{
+ struct mpam_class *class = mpam_resctrl_controls[RDT_RESOURCE_L3].class;
+
+ if (!class)
+ return false;
+
+ return class_has_usable_mba(&class->props);
+}
+
+static void _mpam_resctrl_ctrl_init_mba(struct mpam_resctrl_ctrl *mpam_ctrl,
+ struct mpam_props *cprops,
+ enum resctrl_ctrl_name name)
+{
+ mpam_ctrl->r_ctrl.type = RESCTRL_CTRL_SCALAR;
+ mpam_ctrl->r_ctrl.name = name;
+ INIT_LIST_HEAD_RCU(&mpam_ctrl->r_ctrl.domains);
+ INIT_LIST_HEAD(&mpam_ctrl->r_ctrl.emulated_by);
+
+ __set_bit(RESCTRL_SCALAR_FLAG_LINEAR, mpam_ctrl->r_ctrl.scalar.flags);
+ mpam_ctrl->r_ctrl.scalar.min = get_mba_min(cprops);
+ mpam_ctrl->r_ctrl.scalar.max = MAX_MBA_BW;
+ mpam_ctrl->r_ctrl.scalar.reset_val = MAX_MBA_BW;
+ mpam_ctrl->r_ctrl.scalar.gran = get_mba_granularity(cprops);
+}
+
+static int mpam_resctrl_ctrl_init_mba(struct rdt_resource *r,
+ struct mpam_props *cprops)
+{
+ struct mpam_resctrl_ctrl *ctrl_def, *ctrl_node;
+
+ ctrl_def = kzalloc_obj(*ctrl_def);
+ if (!ctrl_def)
+ return -ENOMEM;
+
+ _mpam_resctrl_ctrl_init_mba(ctrl_def, cprops, RESCTRL_CTRL_NAME_DEF);
+ list_add(&ctrl_def->r_ctrl.entry, &r->controls);
+
+ if (!mpam_resctrl_ctrl_node(r)) {
+ r->ctrl_scope = RESCTRL_L3_CACHE;
+ return 0;
+ }
+
+ /*
+ * The control domains of a memory class follow the memory
+ * controllers, one per NUMA node.
+ */
+ r->ctrl_scope = RESCTRL_NODE;
+
+ /*
+ * When the L3 cache has usable bandwidth control the legacy MB control
+ * is backed by that hardware and needs no emulation.
+ */
+ if (mpam_resctrl_cache_has_mba())
+ return 0;
+
+ ctrl_node = kzalloc_obj(*ctrl_node);
+ if (!ctrl_node)
+ return -ENOMEM;
+
+ _mpam_resctrl_ctrl_init_mba(ctrl_node, cprops, RESCTRL_CTRL_NAME_NODE);
+
+ /*
+ * MB has no bandwidth hardware of its own, so back it with the
+ * node-scoped MB_NODE control. Legacy mode keeps the "MB:" schemata
+ * line for backward compatibility, native mode exposes MB_NODE
+ * instead.
+ */
+ list_add(&ctrl_node->r_ctrl.entry, &ctrl_def->r_ctrl.emulated_by);
+ r->ctrl_mode = RESCTRL_CTRL_MODE_LEGACY;
+
+ return 0;
+}
+
static int mpam_resctrl_control_init(struct mpam_resctrl_res *res)
{
struct mpam_class *class = res->class;
struct mpam_props *cprops = &class->props;
struct rdt_resource *r = &res->resctrl_res;
struct mpam_resctrl_ctrl *mpam_ctrl;
-
- mpam_ctrl = kzalloc_obj(*mpam_ctrl);
- if (!mpam_ctrl)
- return -ENOMEM;
+ int ret;
switch (r->rid) {
case RDT_RESOURCE_L2:
case RDT_RESOURCE_L3:
+ mpam_ctrl = kzalloc_obj(*mpam_ctrl);
+ if (!mpam_ctrl)
+ return -ENOMEM;
+
mpam_ctrl->r_ctrl.type = RESCTRL_CTRL_BITMAP;
mpam_ctrl->r_ctrl.name = RESCTRL_CTRL_NAME_DEF;
INIT_LIST_HEAD_RCU(&mpam_ctrl->r_ctrl.domains);
@@ -1308,20 +1396,11 @@ static int mpam_resctrl_control_init(struct mpam_resctrl_res *res)
r->alloc_capable = true;
break;
case RDT_RESOURCE_MBA:
- r->ctrl_scope = RESCTRL_L3_CACHE;
- mpam_ctrl->r_ctrl.type = RESCTRL_CTRL_SCALAR;
- mpam_ctrl->r_ctrl.name = RESCTRL_CTRL_NAME_DEF;
- INIT_LIST_HEAD_RCU(&mpam_ctrl->r_ctrl.domains);
- INIT_LIST_HEAD(&mpam_ctrl->r_ctrl.emulated_by);
+ ret = mpam_resctrl_ctrl_init_mba(r, cprops);
+ if (ret)
+ return ret;
r->bw_throttle_mode = THREAD_THROTTLE_UNDEFINED;
- __set_bit(RESCTRL_SCALAR_FLAG_LINEAR, mpam_ctrl->r_ctrl.scalar.flags);
- mpam_ctrl->r_ctrl.scalar.min = get_mba_min(cprops);
- mpam_ctrl->r_ctrl.scalar.max = MAX_MBA_BW;
- mpam_ctrl->r_ctrl.scalar.reset_val = MAX_MBA_BW;
- mpam_ctrl->r_ctrl.scalar.gran = get_mba_granularity(cprops);
- list_add(&mpam_ctrl->r_ctrl.entry, &r->controls);
-
r->name = "MB";
r->alloc_capable = true;
break;
@@ -1484,7 +1563,7 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct resctrl_ctrl *ctrl,
struct mpam_props *cprops;
struct mpam_resctrl_res *res;
struct mpam_resctrl_dom *dom;
- enum mpam_device_features configured_by;
+ enum mpam_device_features configured_by = MPAM_FEATURE_LAST;
lockdep_assert_cpus_held();
@@ -1512,16 +1591,26 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct resctrl_ctrl *ctrl,
configured_by = mpam_feat_cpor_part;
break;
case RDT_RESOURCE_MBA:
- if (mpam_has_feature(mpam_feat_mbw_max, cprops)) {
- configured_by = mpam_feat_mbw_max;
+ /*
+ * MB and its emulating MB_NODE control are both backed by the
+ * same MPAM bandwidth partitioning hardware.
+ */
+ switch (ctrl->name) {
+ case RESCTRL_CTRL_NAME_DEF:
+ case RESCTRL_CTRL_NAME_NODE:
+ if (mpam_has_feature(mpam_feat_mbw_max, cprops))
+ configured_by = mpam_feat_mbw_max;
+ break;
+ default:
break;
}
- fallthrough;
+ break;
default:
return resctrl_get_default_ctrlval(ctrl);
}
- if (!r->alloc_capable || partid >= resctrl_arch_get_num_closid(r) ||
+ if (configured_by == MPAM_FEATURE_LAST || !r->alloc_capable ||
+ partid >= resctrl_arch_get_num_closid(r) ||
!mpam_has_feature(configured_by, cfg))
return resctrl_get_default_ctrlval(ctrl);
@@ -1582,12 +1671,19 @@ int resctrl_arch_update_one(struct rdt_resource *r, struct resctrl_ctrl *ctrl,
mpam_set_feature(mpam_feat_cpor_part, &cfg);
break;
case RDT_RESOURCE_MBA:
- if (mpam_has_feature(mpam_feat_mbw_max, cprops)) {
+ switch (ctrl->name) {
+ case RESCTRL_CTRL_NAME_DEF:
+ case RESCTRL_CTRL_NAME_NODE:
+ if (!mpam_has_feature(mpam_feat_mbw_max, cprops))
+ return -EINVAL;
+
cfg.mbw_max = percent_to_mbw_max(cfg_val, cprops);
mpam_set_feature(mpam_feat_mbw_max, &cfg);
break;
+ default:
+ return -EINVAL;
}
- fallthrough;
+ break;
default:
return -EINVAL;
}
@@ -1650,9 +1746,17 @@ int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid)
* controls? How to communicate to user space?
*/
for_each_resource_ctrl(ctrl, r) {
+ struct resctrl_ctrl *em_ctrl;
+
err = _resctrl_arch_update_domains(r, ctrl, closid);
if (err)
return err;
+
+ list_for_each_entry(em_ctrl, &ctrl->emulated_by, entry) {
+ err = _resctrl_arch_update_domains(r, em_ctrl, closid);
+ if (err)
+ return err;
+ }
}
return 0;
@@ -1915,6 +2019,81 @@ mpam_resctrl_get_ctrl_domain_from_cpu(int cpu, struct mpam_resctrl_res *res,
return NULL;
}
+static int mpam_resctrl_online_ctrl(unsigned int cpu, struct mpam_resctrl_res *res,
+ struct resctrl_ctrl *ctrl,
+ struct mpam_component *comp)
+{
+ struct mpam_resctrl_dom *dom;
+
+ dom = mpam_resctrl_get_ctrl_domain_from_cpu(cpu, res, ctrl, comp);
+ if (!dom) {
+ dom = mpam_resctrl_alloc_ctrl_domain(cpu, res, ctrl, comp);
+ if (IS_ERR(dom))
+ return PTR_ERR(dom);
+
+ return 0;
+ }
+
+ mpam_resctrl_online_domain_hdr(cpu, &dom->resctrl_ctrl_dom.hdr);
+
+ return 0;
+}
+
+static void mpam_resctrl_offline_ctrl(unsigned int cpu, struct mpam_resctrl_res *res,
+ struct resctrl_ctrl *ctrl,
+ struct mpam_component *comp)
+{
+ struct rdt_ctrl_domain *ctrl_d;
+ struct mpam_resctrl_dom *dom;
+
+ dom = mpam_resctrl_get_ctrl_domain_from_cpu(cpu, res, ctrl, comp);
+ if (WARN_ON_ONCE(!dom))
+ return;
+
+ ctrl_d = &dom->resctrl_ctrl_dom;
+ if (mpam_resctrl_offline_domain_hdr(cpu, &ctrl_d->hdr)) {
+ resctrl_offline_ctrl_domain(&res->resctrl_res, ctrl, ctrl_d);
+ kfree(dom);
+ }
+}
+
+/* Controls that emulate another control need domains of their own. */
+static int mpam_resctrl_online_ctrls(unsigned int cpu, struct mpam_resctrl_res *res,
+ struct mpam_component *comp)
+{
+ struct rdt_resource *r = &res->resctrl_res;
+ struct resctrl_ctrl *ctrl, *em_ctrl;
+ int err;
+
+ for_each_resource_ctrl(ctrl, r) {
+ err = mpam_resctrl_online_ctrl(cpu, res, ctrl, comp);
+ if (err)
+ return err;
+
+ list_for_each_entry(em_ctrl, &ctrl->emulated_by, entry) {
+ err = mpam_resctrl_online_ctrl(cpu, res, em_ctrl, comp);
+ if (err)
+ return err;
+ }
+ }
+
+ return 0;
+}
+
+static void mpam_resctrl_offline_ctrls(unsigned int cpu, struct mpam_resctrl_res *res,
+ struct mpam_component *comp)
+{
+ struct rdt_resource *r = &res->resctrl_res;
+ struct resctrl_ctrl *ctrl, *em_ctrl;
+
+ for_each_resource_ctrl(ctrl, r) {
+ list_for_each_entry(em_ctrl, &ctrl->emulated_by, entry)
+ mpam_resctrl_offline_ctrl(cpu, res, em_ctrl, comp);
+
+ mpam_resctrl_offline_ctrl(cpu, res, ctrl, comp);
+ }
+}
+
int mpam_resctrl_online_cpu(unsigned int cpu)
{
struct mpam_resctrl_res *res;
@@ -1925,7 +2104,6 @@ int mpam_resctrl_online_cpu(unsigned int cpu)
for_each_mpam_resctrl_control(res, rid) {
struct mpam_resctrl_dom *dom;
struct rdt_resource *r = &res->resctrl_res;
- struct resctrl_ctrl *ctrl;
if (!res->class)
continue; // dummy_resource;
@@ -1937,21 +2115,10 @@ int mpam_resctrl_online_cpu(unsigned int cpu)
continue;
if (r->alloc_capable) {
- for_each_resource_ctrl(ctrl, r) {
- dom = mpam_resctrl_get_ctrl_domain_from_cpu(cpu, res,
- ctrl, comp);
- if (!dom) {
- dom = mpam_resctrl_alloc_ctrl_domain(cpu, res,
- ctrl, comp);
- } else {
- struct rdt_ctrl_domain *ctrl_d =
- &dom->resctrl_ctrl_dom;
-
- mpam_resctrl_online_domain_hdr(cpu, &ctrl_d->hdr);
- }
- if (IS_ERR(dom))
- return PTR_ERR(dom);
- }
+ int err = mpam_resctrl_online_ctrls(cpu, res, comp);
+
+ if (err)
+ return err;
}
if (r->mon_capable) {
dom = mpam_resctrl_get_mon_domain_from_cpu(cpu, res, comp);
@@ -1985,8 +2152,6 @@ void mpam_resctrl_offline_cpu(unsigned int cpu)
for_each_mpam_resctrl_control(res, rid) {
struct mpam_resctrl_dom *dom;
struct rdt_l3_mon_domain *mon_d;
- struct rdt_ctrl_domain *ctrl_d;
- struct resctrl_ctrl *ctrl;
bool dom_empty;
struct rdt_resource *r = &res->resctrl_res;
@@ -1999,22 +2164,8 @@ void mpam_resctrl_offline_cpu(unsigned int cpu)
if (!cpumask_test_cpu(cpu, &comp->affinity))
continue;
- if (r->alloc_capable) {
- for_each_resource_ctrl(ctrl, r) {
- dom = mpam_resctrl_get_ctrl_domain_from_cpu(cpu, res,
- ctrl, comp);
- if (WARN_ON_ONCE(!dom))
- continue;
- ctrl_d = &dom->resctrl_ctrl_dom;
- dom_empty = mpam_resctrl_offline_domain_hdr(cpu,
- &ctrl_d->hdr);
- if (dom_empty) {
- resctrl_offline_ctrl_domain(&res->resctrl_res, ctrl,
- ctrl_d);
- kfree(dom);
- }
- }
- }
+ if (r->alloc_capable)
+ mpam_resctrl_offline_ctrls(cpu, res, comp);
if (r->mon_capable) {
dom = mpam_resctrl_get_mon_domain_from_cpu(cpu, res, comp);
diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index 4bc7090ad0c7..77a2f2e877a6 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -359,6 +359,7 @@ static const char * const resctrl_ctrl_name[] = {
[RESCTRL_CTRL_NAME_DEF] = "",
[RESCTRL_CTRL_NAME_MIN] = "MIN",
[RESCTRL_CTRL_NAME_MAX] = "MAX",
+ [RESCTRL_CTRL_NAME_NODE] = "NODE",
[RESCTRL_CTRL_NAME_REGION0_MIN] = "REGION0_MIN",
[RESCTRL_CTRL_NAME_REGION0_MAX] = "REGION0_MAX",
};
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 195c0948b26d..b8df7489539f 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -398,6 +398,7 @@ struct resctrl_mon {
* has the same name as the resource.
* @RESCTRL_CTRL_NAME_MIN: "MIN"
* @RESCTRL_CTRL_NAME_MAX: "MAX"
+ * @RESCTRL_CTRL_NAME_NODE: "NODE"
* @RESCTRL_CTRL_NAME_REGION0_MIN: "REGION0_MIN"
* @RESCTRL_CTRL_NAME_REGION0_MAX: "REGION0_MAX"
*/
@@ -405,6 +406,7 @@ enum resctrl_ctrl_name {
RESCTRL_CTRL_NAME_DEF,
RESCTRL_CTRL_NAME_MIN,
RESCTRL_CTRL_NAME_MAX,
+ RESCTRL_CTRL_NAME_NODE,
RESCTRL_CTRL_NAME_REGION0_MIN,
RESCTRL_CTRL_NAME_REGION0_MAX,
RESCTRL_CTRL_NAME_LAST = RESCTRL_CTRL_NAME_REGION0_MAX
--
2.53.0
More information about the linux-arm-kernel
mailing list