[RFC PATCH 25/38] arm_mpam: resctrl: Add resctrl_arch_rmid_read() and resctrl_arch_reset_rmid()

James Morse
2025-12-05T22:01:11Z

resctrl uses resctrl_arch_rmid_read() to read counters. CDP emulation
means the counter may need reading in three different ways. The same
goes for reset.

The helpers behind the resctrl_arch_ functions will be re-used for the
ABMC equivalent functions.

Add the rounding helper for checking monitor values while we're here.

Signed-off-by: James Morse <james.morse@arm.com>
---
drivers/resctrl/mpam_resctrl.c | 154 +++++++++++++++++++++++++++++++++
include/linux/arm_mpam.h | 5 ++
2 files changed, 159 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index a2b238d47117..dc8a819d0976 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -355,6 +355,160 @@ void resctrl_arch_mon_ctx_free(struct rdt_resource *r,
resctrl_arch_mon_ctx_free_no_wait(evtid, mon_idx);
}

+static int
+__read_mon(struct mpam_resctrl_mon *mon, struct mpam_component *mon_comp,
+ enum mpam_device_features mon_type,
+ int mon_idx,
+ enum resctrl_conf_type cdp_type, u32 closid, u32 rmid, u64 *val)
+{
+ struct mon_cfg cfg = { };
+
+ if (!mpam_is_enabled())
+ return -EINVAL;
+
+ /* 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) {
+ if (mpam_resctrl_abmc_enabled()) {
+ /* Report Unassigned */
+ return -ENOENT;
+ }
+ /* Report Unavailable */
+ return -EINVAL;
+ }
+ }
+
+ cfg.mon = mon_idx;
+ cfg.match_pmg = true;
+ cfg.partid = closid;
+ cfg.pmg = rmid;
+
+ if (irqs_disabled()) {
+ /* Check if we can access this domain without an IPI */
+ return -EIO;
+ }
+
+ return mpam_msmon_read(mon_comp, &cfg, mon_type, val);
+}
+
+static int read_mon_cdp_safe(struct mpam_resctrl_mon *mon, struct mpam_component *mon_comp,
+ enum mpam_device_features mon_type,
+ int mon_idx, u32 closid, u32 rmid, u64 *val)
+{
+ if (cdp_enabled) {
+ u64 code_val = 0, data_val = 0;
+ int err;
+
+ err = __read_mon(mon, mon_comp, mon_type, mon_idx,
+ CDP_CODE, closid, rmid, &code_val);
+ if (err)
+ return err;
+
+ err = __read_mon(mon, mon_comp, mon_type, mon_idx,
+ CDP_DATA, closid, rmid, &data_val);
+ if (!err)
+ *val += code_val + data_val;
+ return err;
+ }
+
+ return __read_mon(mon, mon_comp, mon_type, mon_idx,
+ CDP_NONE, closid, rmid, val);
+}
+
+/* MBWU when not in ABMC mode, and CSU counters. */
+int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_mon_domain *d,
+ u32 closid, u32 rmid, enum resctrl_event_id eventid,
+ u64 *val, void *arch_mon_ctx)
+{
+ struct mpam_resctrl_dom *l3_dom;
+ struct mpam_component *mon_comp;
+ u32 mon_idx = *(u32 *)arch_mon_ctx;
+ enum mpam_device_features mon_type;
+ struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[eventid];
+
+ resctrl_arch_rmid_read_context_check();
+
+ if (eventid >= QOS_NUM_EVENTS || !mon->class)
+ return -EINVAL;
+
+ l3_dom = container_of(d, struct mpam_resctrl_dom, resctrl_mon_dom);
+ mon_comp = l3_dom->mon_comp[eventid];
+
+ switch (eventid) {
+ case QOS_L3_OCCUP_EVENT_ID:
+ mon_type = mpam_feat_msmon_csu;
+ break;
+ case QOS_L3_MBM_LOCAL_EVENT_ID:
+ case QOS_L3_MBM_TOTAL_EVENT_ID:
+ mon_type = mpam_feat_msmon_mbwu;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return read_mon_cdp_safe(mon, mon_comp, mon_type, mon_idx,
+ 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);
+ }
+}
+
+/* Called via IPI. Call with read_cpus_lock() held. */
+void resctrl_arch_reset_rmid(struct rdt_resource *r, struct rdt_mon_domain *d,
+ u32 closid, u32 rmid, enum resctrl_event_id eventid)
+{
+ struct mpam_resctrl_dom *l3_dom;
+ struct mpam_component *mon_comp;
+ struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[eventid];
+
+ if (!mpam_is_enabled())
+ return;
+
+ /* Only MBWU counters are relevant, and for supported event types. */
+ 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);
+}
+
static bool cache_has_usable_cpor(struct mpam_class *class)
{
struct mpam_props *cprops = &class->props;
diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index e1461e32af75..86d5e326d2bd 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h
@@ -67,6 +67,11 @@ struct rdt_resource;
void *resctrl_arch_mon_ctx_alloc(struct rdt_resource *r, enum resctrl_event_id evtid);
void resctrl_arch_mon_ctx_free(struct rdt_resource *r, enum resctrl_event_id evtid, void *ctx);

+static inline unsigned int resctrl_arch_round_mon_val(unsigned int val)
+{
+ return val;
+}
+
/**
* mpam_register_requestor() - Register a requestor with the MPAM driver
* @partid_max: The maximum PARTID value the requestor can generate.
--
2.39.5