From: Babu Moger Date: Fri, 5 Sep 2025 21:34:09 +0000 (-0500) Subject: fs/resctrl: Introduce the interface to display monitoring modes X-Git-Tag: v6.18-rc1~186^2~24 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=3b497c3f4f0427d940ec5c8600e840c8adc5cfbf;p=thirdparty%2Flinux.git 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 Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Reinette Chatre 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 c97fd77a107dc..b692829fec5f6 100644 --- 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 7a57366d1abce..78aeb7ea38af2 100644 --- 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 b578451de2b50..96231d517e711 100644 --- 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 b6ab107049939..144585a859967 100644 --- 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,