Message-ID: <0a646cf184a9113c54518b14a5c94984b36cee2a.1752013061.git.babu.moger@amd.com>
Date: Tue, 8 Jul 2025 17:17:40 -0500
From: Babu Moger <babu.moger@....com>
To: <corbet@....net>, <tony.luck@...el.com>, <reinette.chatre@...el.com>,
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Subject: [PATCH v15 31/34] fs/resctrl: Introduce the interface to modify assignments in a group

Enable the mbm_l3_assignments resctrl file to be used to modify counter
assignments of CTRL_MON and MON groups when the "mbm_event" counter
assignment mode is enabled.

The assignment modifications are done in the following format:
<Event>:<Domain id>=<Assignment state>

Event: A valid MBM event in the
       /sys/fs/resctrl/info/L3_MON/event_configs directory.

Domain ID: A valid domain ID. When writing, '*' applies the changes
	   to all domains.

Assignment states:

    _ : Unassign the counter.

    e : Assign the counter exclusively.

Examples:

$ cd /sys/fs/resctrl
$ cat /sys/fs/resctrl/mbm_L3_assignments
  mbm_total_bytes:0=e;1=e
  mbm_local_bytes:0=e;1=e

To unassign the counter associated with the mbm_total_bytes event on
domain 0:

$ echo "mbm_total_bytes:0=_" > mbm_L3_assignments
$ cat /sys/fs/resctrl/mbm_L3_assignments
  mbm_total_bytes:0=_;1=e
  mbm_local_bytes:0=e;1=e

To unassign the counter associated with the mbm_total_bytes event on
all the domains:

$ echo "mbm_total_bytes:*=_" > mbm_L3_assignments
$ cat /sys/fs/resctrl/mbm_L3_assignments
  mbm_total_bytes:0=_;1=_
  mbm_local_bytes:0=e;1=e

Signed-off-by: Babu Moger <babu.moger@....com>
---
v15: Updated the changelog little bit.
     Fixed the spacing in event_filter display.
     Removed the enum ASSIGN_NONE etc. Not required anymore.
     Moved mbm_get_mon_event_by_name() to fs/resctrl/monitor.c
     Used the new macro for_each_mon_event().
     Renamed resctrl_get_assign_state() -> rdtgroup_modify_assign_state().
     Quite a few changes in resctrl_process_assign().
     Removed the found and domain variables.
     Called rdtgroup_modify_assign_state() directly where applicable.
     Removed couple of goto statements.

v14: Fixed the problem reported by Peter.
     Updated the changelog.
     Updated the user doc resctrl.rst.
     Added example section on how to use resctrl with mbm_assign_mode.

v13: Few changes in mbm_L3_assignments_write() after moving the event config to evt_list.
     Resolved conflicts caused by the recent FS/ARCH code restructure.

v12: New patch:
     Assignment interface moved inside the group based the discussion
     https://lore.kernel.org/lkml/CALPaoCiii0vXOF06mfV=kVLBzhfNo0SFqt4kQGwGSGVUqvr2Dg@mail.gmail.com/#t
---
 Documentation/filesystems/resctrl.rst | 146 +++++++++++++++++++++++++-
 fs/resctrl/internal.h                 |   2 +
 fs/resctrl/monitor.c                  |  18 ++++
 fs/resctrl/rdtgroup.c                 | 123 +++++++++++++++++++++-
 4 files changed, 287 insertions(+), 2 deletions(-)

diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 4dd1d605d6ad..2b2acb55d8b1 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -527,7 +527,8 @@ When the "mba_MBps" mount option is used all CTRL_MON groups will also contain:
 	Event: A valid MBM event in the
 	       /sys/fs/resctrl/info/L3_MON/event_configs directory.
 
-	Domain ID: A valid domain ID.
+	Domain ID: A valid domain ID. When writing, '*' applies the changes
+		   to all the domains.
 
 	Assignment states:
 
@@ -544,6 +545,34 @@ When the "mba_MBps" mount option is used all CTRL_MON groups will also contain:
 	   mbm_total_bytes:0=e;1=e
 	   mbm_local_bytes:0=e;1=e
 
+	Assignments can be modified by writing to the interface.
+
+	Example:
+	To unassign the counter associated with the mbm_total_bytes event on domain 0:
+	::
+
+	 # echo "mbm_total_bytes:0=_" > /sys/fs/resctrl/mbm_L3_assignments
+	 # cat /sys/fs/resctrl/mbm_L3_assignments
+	   mbm_total_bytes:0=_;1=e
+	   mbm_local_bytes:0=e;1=e
+
+	To unassign the counter associated with the mbm_total_bytes event on all the domains:
+	::
+
+	 # echo "mbm_total_bytes:*=_" > /sys/fs/resctrl/mbm_L3_assignments
+	 # cat /sys/fs/resctrl/mbm_L3_assignments
+	   mbm_total_bytes:0=_;1=_
+	   mbm_local_bytes:0=e;1=e
+
+	To assign the counter associated with the mbm_total_bytes event on all domains in
+	exclusive mode:
+	::
+
+	 # echo "mbm_total_bytes:*=e" > /sys/fs/resctrl/mbm_L3_assignments
+	 # cat /sys/fs/resctrl/mbm_L3_assignments
+	   mbm_total_bytes:0=e;1=e
+	   mbm_local_bytes:0=e;1=e
+
 Resource allocation rules
 -------------------------
 
@@ -1579,6 +1608,121 @@ View the llc occupancy snapshot::
   # cat /sys/fs/resctrl/p1/mon_data/mon_L3_00/llc_occupancy
   11234000
 
+
+Examples on working with mbm_assign_mode
+========================================
+
+a. Check if MBM counter assignment mode is supported.
+::
+
+  #mount -t resctrl resctrl /sys/fs/resctrl/
+
+  # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
+  [mbm_event]
+  default
+
+The "mbm_event" mode is detected and enabled.
+
+b. Check how many assignable counters are supported.
+::
+
+  # cat /sys/fs/resctrl/info/L3_MON/num_mbm_cntrs
+  0=32;1=32
+
+c. Check how many assignable counters are available for assignment in each domain.
+::
+
+  # cat /sys/fs/resctrl/info/L3_MON/available_mbm_cntrs
+  0=30;1=30
+
+d. To list the default group's assign states:
+::
+
+  # cat /sys/fs/resctrl/mbm_L3_assignments
+  mbm_total_bytes:0=e;1=e
+  mbm_local_bytes:0=e;1=e
+
+e.  To unassign the counter associated with the mbm_total_bytes event on domain 0:
+::
+
+  # echo "mbm_total_bytes:0=_" > /sys/fs/resctrl/mbm_L3_assignments
+  # cat /sys/fs/resctrl/mbm_L3_assignments
+  mbm_total_bytes:0=_;1=e
+  mbm_local_bytes:0=e;1=e
+
+f. To unassign the counter associated with the mbm_total_bytes event on all domains:
+::
+
+  # echo "mbm_total_bytes:*=_" > /sys/fs/resctrl/mbm_L3_assignments
+  # cat /sys/fs/resctrl/mbm_L3_assignment
+  mbm_total_bytes:0=_;1=_
+  mbm_local_bytes:0=e;1=e
+
+g. To assign a counter associated with the mbm_total_bytes event on all domains in
+exclusive mode:
+::
+
+  # echo "mbm_total_bytes:*=e" > /sys/fs/resctrl/mbm_L3_assignments
+  # cat /sys/fs/resctrl/mbm_L3_assignments
+  mbm_total_bytes:0=e;1=e
+  mbm_local_bytes:0=e;1=e
+
+h. Read the events mbm_total_bytes and mbm_local_bytes of the default group. There is
+no change in reading the events with the assignment.  If the event is unassigned when
+reading, then the read will come back as "Unassigned".
+::
+
+  # cat /sys/fs/resctrl/mon_data/mon_L3_00/mbm_total_bytes
+  779247936
+  # cat /sys/fs/resctrl/mon_data/mon_L3_00/mbm_local_bytes
+  765207488
+
+i. Check the default event configurations.
+::
+
+  # cat /sys/fs/resctrl/info/L3_MON/event_configs/mbm_total_bytes/event_filter
+  local_reads,remote_reads,local_non_temporal_writes,remote_non_temporal_writes,
+  local_reads_slow_memory,remote_reads_slow_memory,dirty_victim_writes_all
+
+  # cat /sys/fs/resctrl/info/L3_MON/event_configs/mbm_local_bytes/event_filter
+  local_reads,local_non_temporal_writes,local_reads_slow_memory
+
+j. Change the event configuration for mbm_local_bytes.
+::
+
+  # echo "local_reads, local_non_temporal_writes, local_reads_slow_memory, remote_reads" >
+  /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_local_bytes/event_filter
+
+  # cat /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_local_bytes/event_filter
+  local_reads,local_non_temporal_writes,local_reads_slow_memory,remote_reads
+
+This will update all (across all domains of all monitor groups) counter assignments
+associated with the mbm_local_bytes event.
+
+k. Now read the local event again. The first read may come back with "Unavailable"
+status. The subsequent read of mbm_local_bytes will display the current value.
+::
+
+  # cat /sys/fs/resctrl/mon_data/mon_L3_00/mbm_local_bytes
+  Unavailable
+  # cat /sys/fs/resctrl/mon_data/mon_L3_00/mbm_local_bytes
+  314101
+
+l. Users have the option to go back to 'default' mbm_assign_mode if required. This can be
+done using the following command. Note that switching the mbm_assign_mode may reset all
+the MBM counters (and thus all MBM events) of all the resctrl groups.
+::
+
+  # echo "default" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
+  # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
+  mbm_event
+  [default]
+
+m. Unmount the resctrl
+::
+
+  #umount /sys/fs/resctrl/
+
 Intel RDT Errata
 ================
 
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index b42890fd937a..9881674909f2 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -403,6 +403,8 @@ bool closid_allocated(unsigned int closid);
 
 int resctrl_find_cleanest_closid(void);
 
+struct mon_evt *mbm_get_mon_event_by_name(struct rdt_resource *r, char *name);
+
 int rdtgroup_assign_cntr_event(struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
 			       struct mon_evt *mevt);
 void rdtgroup_unassign_cntr_event(struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index e30a867c00bb..61419849b257 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -1220,3 +1220,21 @@ void resctrl_update_cntr_allrdtgrp(struct mon_evt *mevt)
 			rdtgroup_update_cntr_event(r, crgrp, mevt->evtid);
 	}
 }
+
+/*
+ * mbm_get_mon_event_by_name() - Return the mon_evt entry for the matching
+ * event name.
+ */
+struct mon_evt *mbm_get_mon_event_by_name(struct rdt_resource *r, char *name)
+{
+	struct mon_evt *mevt;
+
+	for_each_mon_event(mevt) {
+		if (mevt->rid == r->rid && mevt->enabled &&
+		    resctrl_is_mbm_event(mevt->evtid) &&
+		    !strcmp(mevt->name, name))
+			return mevt;
+	}
+
+	return NULL;
+}
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index dc108c5db298..b26baca389bb 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -2071,6 +2071,126 @@ static int mbm_L3_assignments_show(struct kernfs_open_file *of, struct seq_file
 	return ret;
 }
 
+static int rdtgroup_modify_assign_state(char *assign, struct rdt_mon_domain *d,
+					struct rdtgroup *rdtgrp, struct mon_evt *mevt)
+{
+	int ret = 0;
+
+	if (!assign || strlen(assign) != 1)
+		return -EINVAL;
+
+	switch (*assign) {
+	case 'e':
+		ret = rdtgroup_assign_cntr_event(d, rdtgrp, mevt);
+		break;
+	case '_':
+		rdtgroup_unassign_cntr_event(d, rdtgrp, mevt);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static int resctrl_process_assign(struct rdt_resource *r, struct rdtgroup *rdtgrp,
+				  char *event, char *tok)
+{
+	struct rdt_mon_domain *d;
+	unsigned long dom_id = 0;
+	char *dom_str, *id_str;
+	struct mon_evt *mevt;
+	int ret;
+
+	mevt = mbm_get_mon_event_by_name(r, event);
+	if (!mevt) {
+		rdt_last_cmd_printf("Invalid event %s\n", event);
+		return  -ENOENT;
+	}
+
+next:
+	if (!tok || tok[0] == '\0')
+		return 0;
+
+	/* Start processing the strings for each domain */
+	dom_str = strim(strsep(&tok, ";"));
+
+	id_str = strsep(&dom_str, "=");
+
+	/* Check for domain id '*' which means all domains */
+	if (id_str && *id_str == '*') {
+		ret = rdtgroup_modify_assign_state(dom_str, NULL, rdtgrp, mevt);
+		if (ret)
+			rdt_last_cmd_printf("Assign operation '%s:*=%s' failed\n",
+					    event, dom_str);
+		return ret;
+	} else if (!id_str || kstrtoul(id_str, 10, &dom_id)) {
+		rdt_last_cmd_puts("Missing domain id\n");
+		return -EINVAL;
+	}
+
+	/* Verify if the dom_id is valid */
+	list_for_each_entry(d, &r->mon_domains, hdr.list) {
+		if (d->hdr.id == dom_id) {
+			ret = rdtgroup_modify_assign_state(dom_str, d, rdtgrp, mevt);
+			if (ret) {
+				rdt_last_cmd_printf("Assign operation '%s:%ld=%s' failed\n",
+						    event, dom_id, dom_str);
+				return ret;
+			}
+			goto next;
+		}
+	}
+
+	rdt_last_cmd_printf("Invalid domain id %ld\n", dom_id);
+	return -EINVAL;
+}
+
+static ssize_t mbm_L3_assignments_write(struct kernfs_open_file *of, char *buf,
+					size_t nbytes, loff_t off)
+{
+	struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
+	struct rdtgroup *rdtgrp;
+	char *token, *event;
+	int ret = 0;
+
+	/* Valid input requires a trailing newline */
+	if (nbytes == 0 || buf[nbytes - 1] != '\n')
+		return -EINVAL;
+
+	buf[nbytes - 1] = '\0';
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	if (!rdtgrp) {
+		rdtgroup_kn_unlock(of->kn);
+		return -ENOENT;
+	}
+	rdt_last_cmd_clear();
+
+	if (!resctrl_arch_mbm_cntr_assign_enabled(r)) {
+		rdt_last_cmd_puts("mbm_event mode is not enabled\n");
+		rdtgroup_kn_unlock(of->kn);
+		return -EINVAL;
+	}
+
+	while ((token = strsep(&buf, "\n")) != NULL) {
+		/*
+		 * The write command follows the following format:
+		 * “<Event>:<Domain ID>=<Assignment state>”
+		 * Extract the event name first.
+		 */
+		event = strsep(&token, ":");
+
+		ret = resctrl_process_assign(r, rdtgrp, event, token);
+		if (ret)
+			break;
+	}
+
+	rdtgroup_kn_unlock(of->kn);
+
+	return ret ?: nbytes;
+}
+
 /* rdtgroup information files for one cache resource. */
 static struct rftype res_common_files[] = {
 	{
@@ -2211,9 +2331,10 @@ static struct rftype res_common_files[] = {
 	},
 	{
 		.name		= "mbm_L3_assignments",
-		.mode		= 0444,
+		.mode		= 0644,
 		.kf_ops		= &rdtgroup_kf_single_ops,
 		.seq_show	= mbm_L3_assignments_show,
+		.write		= mbm_L3_assignments_write,
 	},
 	{
 		.name		= "mbm_assign_mode",
-- 
2.34.1

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