fs/resctrl: Add the functionality to assign MBM events

When supported, "mbm_event" counter assignment mode offers "num_mbm_cntrs"
number of counters that can be assigned to RMID, event pairs and monitor
bandwidth usage as long as it is assigned.

Add the functionality to allocate and assign a counter to an RMID, event
pair in the domain. Also, add the helper rdtgroup_assign_cntrs() to assign
counters in the group.

Log the error message "Failed to allocate counter for <event> in domain
<id>" in /sys/fs/resctrl/info/last_cmd_status if all the counters are in
use. Exit on the first failure when assigning counters across all the
domains.

Signed-off-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com

fs/resctrl/internal.h

@@ -396,6 +396,8 @@ int resctrl_num_mbm_cntrs_show(struct kernfs_open_file *of, struct seq_file *s,
 int resctrl_available_mbm_cntrs_show(struct kernfs_open_file *of, struct seq_file *s,
 				     void *v);
 
+void rdtgroup_assign_cntrs(struct rdtgroup *rdtgrp);
+
 #ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
 int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);
 

fs/resctrl/monitor.c

@@ -356,6 +356,55 @@ static struct mbm_state *get_mbm_state(struct rdt_mon_domain *d, u32 closid,
 	return state ? &state[idx] : NULL;
 }
 
+/*
+ * mbm_cntr_get() - Return the counter ID for the matching @evtid and @rdtgrp.
+ *
+ * Return:
+ * Valid counter ID on success, or -ENOENT on failure.
+ */
+static int mbm_cntr_get(struct rdt_resource *r, struct rdt_mon_domain *d,
+			struct rdtgroup *rdtgrp, enum resctrl_event_id evtid)
+{
+	int cntr_id;
+
+	if (!r->mon.mbm_cntr_assignable)
+		return -ENOENT;
+
+	if (!resctrl_is_mbm_event(evtid))
+		return -ENOENT;
+
+	for (cntr_id = 0; cntr_id < r->mon.num_mbm_cntrs; cntr_id++) {
+		if (d->cntr_cfg[cntr_id].rdtgrp == rdtgrp &&
+		    d->cntr_cfg[cntr_id].evtid == evtid)
+			return cntr_id;
+	}
+
+	return -ENOENT;
+}
+
+/*
+ * mbm_cntr_alloc() - Initialize and return a new counter ID in the domain @d.
+ * Caller must ensure that the specified event is not assigned already.
+ *
+ * Return:
+ * Valid counter ID on success, or -ENOSPC on failure.
+ */
+static int mbm_cntr_alloc(struct rdt_resource *r, struct rdt_mon_domain *d,
+			  struct rdtgroup *rdtgrp, enum resctrl_event_id evtid)
+{
+	int cntr_id;
+
+	for (cntr_id = 0; cntr_id < r->mon.num_mbm_cntrs; cntr_id++) {
+		if (!d->cntr_cfg[cntr_id].rdtgrp) {
+			d->cntr_cfg[cntr_id].rdtgrp = rdtgrp;
+			d->cntr_cfg[cntr_id].evtid = evtid;
+			return cntr_id;
+		}
+	}
+
+	return -ENOSPC;
+}
+
 static int __mon_event_count(u32 closid, u32 rmid, struct rmid_read *rr)
 {
 	int cpu = smp_processor_id();
@@ -887,6 +936,113 @@ u32 resctrl_get_mon_evt_cfg(enum resctrl_event_id evtid)
 	return mon_event_all[evtid].evt_cfg;
 }
 
+/*
+ * rdtgroup_assign_cntr() - Assign/unassign the counter ID for the event, RMID
+ * pair in the domain.
+ *
+ * Assign the counter if @assign is true else unassign the counter. Reset the
+ * associated non-architectural state.
+ */
+static void rdtgroup_assign_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
+				 enum resctrl_event_id evtid, u32 rmid, u32 closid,
+				 u32 cntr_id, bool assign)
+{
+	struct mbm_state *m;
+
+	resctrl_arch_config_cntr(r, d, evtid, rmid, closid, cntr_id, assign);
+
+	m = get_mbm_state(d, closid, rmid, evtid);
+	if (m)
+		memset(m, 0, sizeof(*m));
+}
+
+/*
+ * rdtgroup_alloc_assign_cntr() - Allocate a counter ID and assign it to the event
+ * pointed to by @mevt and the resctrl group @rdtgrp within the domain @d.
+ *
+ * Return:
+ * 0 on success, < 0 on failure.
+ */
+static int rdtgroup_alloc_assign_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
+				      struct rdtgroup *rdtgrp, struct mon_evt *mevt)
+{
+	int cntr_id;
+
+	/* No action required if the counter is assigned already. */
+	cntr_id = mbm_cntr_get(r, d, rdtgrp, mevt->evtid);
+	if (cntr_id >= 0)
+		return 0;
+
+	cntr_id = mbm_cntr_alloc(r, d, rdtgrp, mevt->evtid);
+	if (cntr_id < 0) {
+		rdt_last_cmd_printf("Failed to allocate counter for %s in domain %d\n",
+				    mevt->name, d->hdr.id);
+		return cntr_id;
+	}
+
+	rdtgroup_assign_cntr(r, d, mevt->evtid, rdtgrp->mon.rmid, rdtgrp->closid, cntr_id, true);
+
+	return 0;
+}
+
+/*
+ * rdtgroup_assign_cntr_event() - Assign a hardware counter for the event in
+ * @mevt to the resctrl group @rdtgrp. Assign counters to all domains if @d is
+ * NULL; otherwise, assign the counter to the specified domain @d.
+ *
+ * If all counters in a domain are already in use, rdtgroup_alloc_assign_cntr()
+ * will fail. The assignment process will abort at the first failure encountered
+ * during domain traversal, which may result in the event being only partially
+ * assigned.
+ *
+ * Return:
+ * 0 on success, < 0 on failure.
+ */
+static int rdtgroup_assign_cntr_event(struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
+				      struct mon_evt *mevt)
+{
+	struct rdt_resource *r = resctrl_arch_get_resource(mevt->rid);
+	int ret = 0;
+
+	if (!d) {
+		list_for_each_entry(d, &r->mon_domains, hdr.list) {
+			ret = rdtgroup_alloc_assign_cntr(r, d, rdtgrp, mevt);
+			if (ret)
+				return ret;
+		}
+	} else {
+		ret = rdtgroup_alloc_assign_cntr(r, d, rdtgrp, mevt);
+	}
+
+	return ret;
+}
+
+/*
+ * rdtgroup_assign_cntrs() - Assign counters to MBM events. Called when
+ *			     a new group is created.
+ *
+ * Each group can accommodate two counters per domain: one for the total
+ * event and one for the local event. Assignments may fail due to the limited
+ * number of counters. However, it is not necessary to fail the group creation
+ * and thus no failure is returned. Users have the option to modify the
+ * counter assignments after the group has been created.
+ */
+void rdtgroup_assign_cntrs(struct rdtgroup *rdtgrp)
+{
+	struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
+
+	if (!r->mon_capable || !resctrl_arch_mbm_cntr_assign_enabled(r))
+		return;
+
+	if (resctrl_is_mon_event_enabled(QOS_L3_MBM_TOTAL_EVENT_ID))
+		rdtgroup_assign_cntr_event(NULL, rdtgrp,
+					   &mon_event_all[QOS_L3_MBM_TOTAL_EVENT_ID]);
+
+	if (resctrl_is_mon_event_enabled(QOS_L3_MBM_LOCAL_EVENT_ID))
+		rdtgroup_assign_cntr_event(NULL, rdtgrp,
+					   &mon_event_all[QOS_L3_MBM_LOCAL_EVENT_ID]);
+}
+
 int resctrl_mbm_assign_mode_show(struct kernfs_open_file *of,
 				 struct seq_file *s, void *v)
 {