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Message-ID: <175793564174.709179.1003557688903099.tip-bot2@tip-bot2>
Date: Mon, 15 Sep 2025 11:27:21 -0000
From: "tip-bot2 for Babu Moger" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Babu Moger <babu.moger@....com>, "Borislav Petkov (AMD)" <bp@...en8.de>,
Reinette Chatre <reinette.chatre@...el.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/cache] fs/resctrl: Introduce the interface to switch
between monitor modes
The following commit has been merged into the x86/cache branch of tip:
Commit-ID: 8004ea01cf6338298e0c6ab055bc3ec659ce381b
Gitweb: https://git.kernel.org/tip/8004ea01cf6338298e0c6ab055bc3ec659ce381b
Author: Babu Moger <babu.moger@....com>
AuthorDate: Fri, 05 Sep 2025 16:34:30 -05:00
Committer: Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Mon, 15 Sep 2025 12:49:18 +02:00
fs/resctrl: Introduce the interface to switch between monitor modes
Resctrl subsystem can support two monitoring modes, "mbm_event" or "default".
In mbm_event mode, monitoring event can only accumulate data while it is
backed by a hardware counter. In "default" mode, resctrl assumes there is
a hardware counter for each event within every CTRL_MON and MON group.
Introduce mbm_assign_mode resctrl file to switch between mbm_event and default
modes.
Example:
To list the MBM monitor modes supported:
$ cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
[mbm_event]
default
To enable the "mbm_event" counter assignment mode:
$ echo "mbm_event" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
To enable the "default" monitoring mode:
$ echo "default" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
Reset MBM event counters automatically as part of changing the mode. Clear
both architectural and non-architectural event states to prevent overflow
conditions during the next event read. Clear assignable counter configuration
on all the domains. Also, enable auto assignment when switching to "mbm_event"
mode.
Signed-off-by: Babu Moger <babu.moger@....com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com
---
Documentation/filesystems/resctrl.rst | 22 +++++-
fs/resctrl/internal.h | 6 ++-
fs/resctrl/monitor.c | 100 +++++++++++++++++++++++++-
fs/resctrl/rdtgroup.c | 7 +-
4 files changed, 131 insertions(+), 4 deletions(-)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index f60f6a9..006d23a 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -259,7 +259,8 @@ with the following files:
"mbm_assign_mode":
The supported counter assignment modes. The enclosed brackets indicate which mode
- is enabled.
+ is enabled. The MBM events associated with counters may reset when "mbm_assign_mode"
+ is changed.
::
# cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
@@ -279,6 +280,15 @@ with the following files:
of counters available is described in the "num_mbm_cntrs" file. Changing the
mode may cause all counters on the resource to reset.
+ Moving to mbm_event counter assignment mode requires users to assign the counters
+ to the events. Otherwise, the MBM event counters will return 'Unassigned' when read.
+
+ The mode is beneficial for AMD platforms that support more CTRL_MON
+ and MON groups than available hardware counters. By default, this
+ feature is enabled on AMD platforms with the ABMC (Assignable Bandwidth
+ Monitoring Counters) capability, ensuring counters remain assigned even
+ when the corresponding RMID is not actively used by any processor.
+
"default":
In default mode, resctrl assumes there is a hardware counter for each
@@ -288,6 +298,16 @@ with the following files:
result in misleading values or display "Unavailable" if no counter is assigned
to the event.
+ * To enable "mbm_event" counter assignment mode:
+ ::
+
+ # echo "mbm_event" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
+
+ * To enable "default" monitoring mode:
+ ::
+
+ # echo "default" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
+
"num_mbm_cntrs":
The maximum number of counters (total of available and assigned counters) in
each domain when the system supports mbm_event mode.
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index c69b1da..cf1fd82 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -396,6 +396,12 @@ void *rdt_kn_parent_priv(struct kernfs_node *kn);
int resctrl_mbm_assign_mode_show(struct kernfs_open_file *of, struct seq_file *s, void *v);
+ssize_t resctrl_mbm_assign_mode_write(struct kernfs_open_file *of, char *buf,
+ size_t nbytes, loff_t off);
+
+void resctrl_bmec_files_show(struct rdt_resource *r, struct kernfs_node *l3_mon_kn,
+ bool show);
+
int resctrl_num_mbm_cntrs_show(struct kernfs_open_file *of, struct seq_file *s, void *v);
int resctrl_available_mbm_cntrs_show(struct kernfs_open_file *of, struct seq_file *s,
diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index f388dbc..50c2446 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -1079,6 +1079,33 @@ out_unlock:
}
/*
+ * mbm_cntr_free_all() - Clear all the counter ID configuration details in the
+ * domain @d. Called when mbm_assign_mode is changed.
+ */
+static void mbm_cntr_free_all(struct rdt_resource *r, struct rdt_mon_domain *d)
+{
+ memset(d->cntr_cfg, 0, sizeof(*d->cntr_cfg) * r->mon.num_mbm_cntrs);
+}
+
+/*
+ * resctrl_reset_rmid_all() - Reset all non-architecture states for all the
+ * supported RMIDs.
+ */
+static void resctrl_reset_rmid_all(struct rdt_resource *r, struct rdt_mon_domain *d)
+{
+ u32 idx_limit = resctrl_arch_system_num_rmid_idx();
+ enum resctrl_event_id evt;
+ int idx;
+
+ for_each_mbm_event_id(evt) {
+ if (!resctrl_is_mon_event_enabled(evt))
+ continue;
+ idx = MBM_STATE_IDX(evt);
+ memset(d->mbm_states[idx], 0, sizeof(*d->mbm_states[0]) * idx_limit);
+ }
+}
+
+/*
* rdtgroup_assign_cntr() - Assign/unassign the counter ID for the event, RMID
* pair in the domain.
*
@@ -1388,6 +1415,79 @@ int resctrl_mbm_assign_mode_show(struct kernfs_open_file *of,
return 0;
}
+ssize_t resctrl_mbm_assign_mode_write(struct kernfs_open_file *of, char *buf,
+ size_t nbytes, loff_t off)
+{
+ struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
+ struct rdt_mon_domain *d;
+ int ret = 0;
+ bool enable;
+
+ /* 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();
+
+ if (!strcmp(buf, "default")) {
+ enable = 0;
+ } else if (!strcmp(buf, "mbm_event")) {
+ if (r->mon.mbm_cntr_assignable) {
+ enable = 1;
+ } else {
+ ret = -EINVAL;
+ rdt_last_cmd_puts("mbm_event mode is not supported\n");
+ goto out_unlock;
+ }
+ } else {
+ ret = -EINVAL;
+ rdt_last_cmd_puts("Unsupported assign mode\n");
+ goto out_unlock;
+ }
+
+ if (enable != resctrl_arch_mbm_cntr_assign_enabled(r)) {
+ ret = resctrl_arch_mbm_cntr_assign_set(r, enable);
+ if (ret)
+ goto out_unlock;
+
+ /* Update the visibility of BMEC related files */
+ resctrl_bmec_files_show(r, NULL, !enable);
+
+ /*
+ * Initialize the default memory transaction values for
+ * total and local events.
+ */
+ if (resctrl_is_mon_event_enabled(QOS_L3_MBM_TOTAL_EVENT_ID))
+ mon_event_all[QOS_L3_MBM_TOTAL_EVENT_ID].evt_cfg = r->mon.mbm_cfg_mask;
+ if (resctrl_is_mon_event_enabled(QOS_L3_MBM_LOCAL_EVENT_ID))
+ mon_event_all[QOS_L3_MBM_LOCAL_EVENT_ID].evt_cfg = r->mon.mbm_cfg_mask &
+ (READS_TO_LOCAL_MEM |
+ READS_TO_LOCAL_S_MEM |
+ NON_TEMP_WRITE_TO_LOCAL_MEM);
+ /* Enable auto assignment when switching to "mbm_event" mode */
+ if (enable)
+ r->mon.mbm_assign_on_mkdir = true;
+ /*
+ * Reset all the non-achitectural RMID state and assignable counters.
+ */
+ list_for_each_entry(d, &r->mon_domains, hdr.list) {
+ mbm_cntr_free_all(r, d);
+ resctrl_reset_rmid_all(r, d);
+ }
+ }
+
+out_unlock:
+ mutex_unlock(&rdtgroup_mutex);
+ cpus_read_unlock();
+
+ return ret ?: nbytes;
+}
+
int resctrl_num_mbm_cntrs_show(struct kernfs_open_file *of,
struct seq_file *s, void *v)
{
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 0c404a1..0320360 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1807,8 +1807,8 @@ static ssize_t mbm_local_bytes_config_write(struct kernfs_open_file *of,
* Don't treat kernfs_find_and_get failure as an error, since this function may
* be called regardless of whether BMEC is supported or the event is enabled.
*/
-static void resctrl_bmec_files_show(struct rdt_resource *r, struct kernfs_node *l3_mon_kn,
- bool show)
+void resctrl_bmec_files_show(struct rdt_resource *r, struct kernfs_node *l3_mon_kn,
+ bool show)
{
struct kernfs_node *kn_config, *mon_kn = NULL;
char name[32];
@@ -1985,9 +1985,10 @@ static struct rftype res_common_files[] = {
},
{
.name = "mbm_assign_mode",
- .mode = 0444,
+ .mode = 0644,
.kf_ops = &rdtgroup_kf_single_ops,
.seq_show = resctrl_mbm_assign_mode_show,
+ .write = resctrl_mbm_assign_mode_write,
.fflags = RFTYPE_MON_INFO | RFTYPE_RES_CACHE,
},
{
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