fs/resctrl: Provide interface to update the event configurations

When "mbm_event" counter assignment mode is enabled, users can modify the
event configuration by writing to the 'event_filter' resctrl file.  The event
configurations for mbm_event mode are located in
/sys/fs/resctrl/info/L3_MON/event_configs/.

Update the assignments of all CTRL_MON and MON resource groups when the event
configuration is modified.

Example:
  $ mount -t resctrl resctrl /sys/fs/resctrl

  $ cd /sys/fs/resctrl/

  $ cat info/L3_MON/event_configs/mbm_local_bytes/event_filter
    local_reads,local_non_temporal_writes,local_reads_slow_memory

  $ echo "local_reads,local_non_temporal_writes" >
    info/L3_MON/event_configs/mbm_total_bytes/event_filter

  $ cat info/L3_MON/event_configs/mbm_total_bytes/event_filter
    local_reads,local_non_temporal_writes

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

Documentation/filesystems/resctrl.rst

@@ -343,6 +343,18 @@ with the following files:
 	  # cat /sys/fs/resctrl/info/L3_MON/event_configs/mbm_local_bytes/event_filter
 	  local_reads,local_non_temporal_writes,local_reads_slow_memory
 
+	Modify the event configuration by writing to the "event_filter" file within
+	the "event_configs" directory. The read/write "event_filter" file contains the
+	configuration of the event that reflects which memory transactions are counted by it.
+
+	For example::
+
+	  # echo "local_reads, local_non_temporal_writes" >
+	    /sys/fs/resctrl/info/L3_MON/event_configs/mbm_total_bytes/event_filter
+
+	  # cat /sys/fs/resctrl/info/L3_MON/event_configs/mbm_total_bytes/event_filter
+	   local_reads,local_non_temporal_writes
+
 "max_threshold_occupancy":
 		Read/write file provides the largest value (in
 		bytes) at which a previously used LLC_occupancy

fs/resctrl/internal.h

@@ -407,6 +407,9 @@ void rdtgroup_unassign_cntrs(struct rdtgroup *rdtgrp);
 
 int event_filter_show(struct kernfs_open_file *of, struct seq_file *seq, void *v);
 
+ssize_t event_filter_write(struct kernfs_open_file *of, char *buf, size_t nbytes,
+			   loff_t off);
+
 #ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
 int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);
 

fs/resctrl/monitor.c

@@ -1192,6 +1192,120 @@ void rdtgroup_unassign_cntrs(struct rdtgroup *rdtgrp)
 					     &mon_event_all[QOS_L3_MBM_LOCAL_EVENT_ID]);
 }
 
+static int resctrl_parse_mem_transactions(char *tok, u32 *val)
+{
+	u32 temp_val = 0;
+	char *evt_str;
+	bool found;
+	int i;
+
+next_config:
+	if (!tok || tok[0] == '\0') {
+		*val = temp_val;
+		return 0;
+	}
+
+	/* Start processing the strings for each memory transaction type */
+	evt_str = strim(strsep(&tok, ","));
+	found = false;
+	for (i = 0; i < NUM_MBM_TRANSACTIONS; i++) {
+		if (!strcmp(mbm_transactions[i].name, evt_str)) {
+			temp_val |= mbm_transactions[i].val;
+			found = true;
+			break;
+		}
+	}
+
+	if (!found) {
+		rdt_last_cmd_printf("Invalid memory transaction type %s\n", evt_str);
+		return -EINVAL;
+	}
+
+	goto next_config;
+}
+
+/*
+ * rdtgroup_update_cntr_event - Update the counter assignments for the event
+ *				in a group.
+ * @r:		Resource to which update needs to be done.
+ * @rdtgrp:	Resctrl group.
+ * @evtid:	MBM monitor event.
+ */
+static void rdtgroup_update_cntr_event(struct rdt_resource *r, struct rdtgroup *rdtgrp,
+				       enum resctrl_event_id evtid)
+{
+	struct rdt_mon_domain *d;
+	int cntr_id;
+
+	list_for_each_entry(d, &r->mon_domains, hdr.list) {
+		cntr_id = mbm_cntr_get(r, d, rdtgrp, evtid);
+		if (cntr_id >= 0)
+			rdtgroup_assign_cntr(r, d, evtid, rdtgrp->mon.rmid,
+					     rdtgrp->closid, cntr_id, true);
+	}
+}
+
+/*
+ * resctrl_update_cntr_allrdtgrp - Update the counter assignments for the event
+ *				   for all the groups.
+ * @mevt	MBM Monitor event.
+ */
+static void resctrl_update_cntr_allrdtgrp(struct mon_evt *mevt)
+{
+	struct rdt_resource *r = resctrl_arch_get_resource(mevt->rid);
+	struct rdtgroup *prgrp, *crgrp;
+
+	/*
+	 * Find all the groups where the event is assigned and update the
+	 * configuration of existing assignments.
+	 */
+	list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {
+		rdtgroup_update_cntr_event(r, prgrp, mevt->evtid);
+
+		list_for_each_entry(crgrp, &prgrp->mon.crdtgrp_list, mon.crdtgrp_list)
+			rdtgroup_update_cntr_event(r, crgrp, mevt->evtid);
+	}
+}
+
+ssize_t event_filter_write(struct kernfs_open_file *of, char *buf, size_t nbytes,
+			   loff_t off)
+{
+	struct mon_evt *mevt = rdt_kn_parent_priv(of->kn);
+	struct rdt_resource *r;
+	u32 evt_cfg = 0;
+	int ret = 0;
+
+	/* Valid input requires a trailing newline */
+	if (nbytes == 0 || buf[nbytes - 1] != '\n')
+		return -EINVAL;
+
+	buf[nbytes - 1] = '\0';
+
+	cpus_read_lock();
+	mutex_lock(&rdtgroup_mutex);
+
+	rdt_last_cmd_clear();
+
+	r = resctrl_arch_get_resource(mevt->rid);
+	if (!resctrl_arch_mbm_cntr_assign_enabled(r)) {
+		rdt_last_cmd_puts("mbm_event counter assignment mode is not enabled\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	ret = resctrl_parse_mem_transactions(buf, &evt_cfg);
+	if (!ret && mevt->evt_cfg != evt_cfg) {
+		mevt->evt_cfg = evt_cfg;
+		resctrl_update_cntr_allrdtgrp(mevt);
+	}
+
+out_unlock:
+	mutex_unlock(&rdtgroup_mutex);
+	cpus_read_unlock();
+
+	return ret ?: nbytes;
+}
+
 int resctrl_mbm_assign_mode_show(struct kernfs_open_file *of,
 				 struct seq_file *s, void *v)
 {

fs/resctrl/rdtgroup.c

@@ -1925,9 +1925,10 @@ static struct rftype res_common_files[] = {
 	},
 	{
 		.name		= "event_filter",
-		.mode		= 0444,
+		.mode		= 0644,
 		.kf_ops		= &rdtgroup_kf_single_ops,
 		.seq_show	= event_filter_show,
+		.write		= event_filter_write,
 	},
 	{
 		.name		= "mbm_assign_mode",