fs/resctrl: Introduce the interface to display monitoring modes

Introduce the resctrl file "mbm_assign_mode" to list the supported counter
assignment modes.

The "mbm_event" counter assignment mode allows users to assign a hardware
counter to an RMID, event pair and monitor bandwidth usage as long as it is
assigned. The hardware continues to track the assigned counter until it is
explicitly unassigned by the user. Each event within a resctrl group can be
assigned independently in this mode.

On AMD systems "mbm_event" mode is backed by the ABMC (Assignable Bandwidth
Monitoring Counters) hardware feature and is enabled by default.

The "default" mode is the existing mode that works without the explicit
counter assignment, instead relying on dynamic counter assignment by hardware
that may result in hardware not dedicating a counter resulting in monitoring
data reads returning "Unavailable".

Provide an interface to display the monitor modes on the system.

  $ cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
  [mbm_event]
  default

Add IS_ENABLED(CONFIG_RESCTRL_ASSIGN_FIXED) check to support Arm64.

On x86, CONFIG_RESCTRL_ASSIGN_FIXED is not defined. On Arm64, it will be
defined when the "mbm_event" mode is supported.

Add IS_ENABLED(CONFIG_RESCTRL_ASSIGN_FIXED) check early to ensure the user
interface remains compatible with upcoming Arm64 support. IS_ENABLED() safely
evaluates to 0 when the configuration is not defined.

As a result, for MPAM, the display would be either:

  [default]

or

  [mbm_event]

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

diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index c97fd77a107dc6ed15b3f6e32be45858595daf8f..b692829fec5f6bb6effe23d77a28ac7e2c62cdbd 100644 (file)
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -257,6 +257,37 @@ with the following files:
            # cat /sys/fs/resctrl/info/L3_MON/mbm_local_bytes_config
            0=0x30;1=0x30;3=0x15;4=0x15
 
+"mbm_assign_mode":
+       The supported counter assignment modes. The enclosed brackets indicate which mode
+       is enabled.
+       ::
+
+         # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
+         [mbm_event]
+         default
+
+       "mbm_event":
+
+       mbm_event mode allows users to assign a hardware counter to an RMID, event
+       pair and monitor the bandwidth usage as long as it is assigned. The hardware
+       continues to track the assigned counter until it is explicitly unassigned by
+       the user. Each event within a resctrl group can be assigned independently.
+
+       In this mode, a monitoring event can only accumulate data while it is backed
+       by a hardware counter. Use "mbm_L3_assignments" found in each CTRL_MON and MON
+       group to specify which of the events should have a counter assigned. The number
+       of counters available is described in the "num_mbm_cntrs" file. Changing the
+       mode may cause all counters on the resource to reset.
+
+       "default":
+
+       In default mode, resctrl assumes there is a hardware counter for each
+       event within every CTRL_MON and MON group. On AMD platforms, it is
+       recommended to use the mbm_event mode, if supported, to prevent reset of MBM
+       events between reads resulting from hardware re-allocating counters. This can
+       result in misleading values or display "Unavailable" if no counter is assigned
+       to the event.
+
 "max_threshold_occupancy":
                Read/write file provides the largest value (in
                bytes) at which a previously used LLC_occupancy

diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index 7a57366d1abce73cb6fd9716a8cd061fea1e961e..78aeb7ea38af2634a24d3c7ec9bd50725459fcd1 100644 (file)
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -382,6 +382,10 @@ bool closid_allocated(unsigned int closid);
 
 int resctrl_find_cleanest_closid(void);
 
+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);
+
 #ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
 int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);
 

diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index b578451de2b50b7dfa44c358d7d812d599e65aaa..96231d517e711d4506463b468e0a359cdc26d3e5 100644 (file)
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -882,6 +882,36 @@ bool resctrl_is_mon_event_enabled(enum resctrl_event_id eventid)
               mon_event_all[eventid].enabled;
 }
 
+int resctrl_mbm_assign_mode_show(struct kernfs_open_file *of,
+                                struct seq_file *s, void *v)
+{
+       struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
+       bool enabled;
+
+       mutex_lock(&rdtgroup_mutex);
+       enabled = resctrl_arch_mbm_cntr_assign_enabled(r);
+
+       if (r->mon.mbm_cntr_assignable) {
+               if (enabled)
+                       seq_puts(s, "[mbm_event]\n");
+               else
+                       seq_puts(s, "[default]\n");
+
+               if (!IS_ENABLED(CONFIG_RESCTRL_ASSIGN_FIXED)) {
+                       if (enabled)
+                               seq_puts(s, "default\n");
+                       else
+                               seq_puts(s, "mbm_event\n");
+               }
+       } else {
+               seq_puts(s, "[default]\n");
+       }
+
+       mutex_unlock(&rdtgroup_mutex);
+
+       return 0;
+}
+
 /**
  * resctrl_mon_resource_init() - Initialise global monitoring structures.
  *

diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index b6ab107049939a62f47ac633b728e967bf65ecdd..144585a8599670e2ce0a8beb9cd32d82d814a076 100644 (file)
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -975,7 +975,7 @@ static int rdt_last_cmd_status_show(struct kernfs_open_file *of,
        return 0;
 }
 
-static void *rdt_kn_parent_priv(struct kernfs_node *kn)
+void *rdt_kn_parent_priv(struct kernfs_node *kn)
 {
        /*
         * The parent pointer is only valid within RCU section since it can be
@@ -1911,6 +1911,13 @@ static struct rftype res_common_files[] = {
                .seq_show       = mbm_local_bytes_config_show,
                .write          = mbm_local_bytes_config_write,
        },
+       {
+               .name           = "mbm_assign_mode",
+               .mode           = 0444,
+               .kf_ops         = &rdtgroup_kf_single_ops,
+               .seq_show       = resctrl_mbm_assign_mode_show,
+               .fflags         = RFTYPE_MON_INFO | RFTYPE_RES_CACHE,
+       },
        {
                .name           = "cpus",
                .mode           = 0644,