fs/resctrl: Add the functionality to unassign MBM events

The "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. If all the counters are in use, the kernel logs the
error message "Failed to allocate counter for <event> in domain <id>" in
/sys/fs/resctrl/info/last_cmd_status when a new assignment is requested.

To make space for a new assignment, users must unassign an already assigned
counter and retry the assignment again.

Add the functionality to unassign and free the counters in the domain.  Also,
add the helper rdtgroup_unassign_cntrs() to unassign counters in the group.

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

1 files changed, 66 insertions, 0 deletions

diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index 106e9bdb8a9d..2ed29ae831a4 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -405,6 +405,14 @@ static int mbm_cntr_alloc(struct rdt_resource *r, struct rdt_mon_domain *d,
 	return -ENOSPC;
 }
 
+/*
+ * mbm_cntr_free() - Clear the counter ID configuration details in the domain @d.
+ */
+static void mbm_cntr_free(struct rdt_mon_domain *d, int cntr_id)
+{
+	memset(&d->cntr_cfg[cntr_id], 0, sizeof(*d->cntr_cfg));
+}
+
 static int __mon_event_count(u32 closid, u32 rmid, struct rmid_read *rr)
 {
 	int cpu = smp_processor_id();
@@ -1043,6 +1051,64 @@ void rdtgroup_assign_cntrs(struct rdtgroup *rdtgrp)
 					   &mon_event_all[QOS_L3_MBM_LOCAL_EVENT_ID]);
 }
 
+/*
+ * rdtgroup_free_unassign_cntr() - Unassign and reset the counter ID configuration
+ * for the event pointed to by @mevt within the domain @d and resctrl group @rdtgrp.
+ */
+static void rdtgroup_free_unassign_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
+					struct rdtgroup *rdtgrp, struct mon_evt *mevt)
+{
+	int cntr_id;
+
+	cntr_id = mbm_cntr_get(r, d, rdtgrp, mevt->evtid);
+
+	/* If there is no cntr_id assigned, nothing to do */
+	if (cntr_id < 0)
+		return;
+
+	rdtgroup_assign_cntr(r, d, mevt->evtid, rdtgrp->mon.rmid, rdtgrp->closid, cntr_id, false);
+
+	mbm_cntr_free(d, cntr_id);
+}
+
+/*
+ * rdtgroup_unassign_cntr_event() - Unassign a hardware counter associated with
+ * the event structure @mevt from the domain @d and the group @rdtgrp. Unassign
+ * the counters from all the domains if @d is NULL else unassign from @d.
+ */
+static void rdtgroup_unassign_cntr_event(struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
+					 struct mon_evt *mevt)
+{
+	struct rdt_resource *r = resctrl_arch_get_resource(mevt->rid);
+
+	if (!d) {
+		list_for_each_entry(d, &r->mon_domains, hdr.list)
+			rdtgroup_free_unassign_cntr(r, d, rdtgrp, mevt);
+	} else {
+		rdtgroup_free_unassign_cntr(r, d, rdtgrp, mevt);
+	}
+}
+
+/*
+ * rdtgroup_unassign_cntrs() - Unassign the counters associated with MBM events.
+ *			       Called when a group is deleted.
+ */
+void rdtgroup_unassign_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_unassign_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_unassign_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)
 {