Commit 3b497c3f authored by Babu Moger's avatar Babu Moger Committed by Borislav Petkov (AMD)
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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: default avatarBabu Moger <babu.moger@amd.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: default avatarReinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com
parent faebbc58

Documentation/filesystems/resctrl.rst

+31 −0
Original line number Diff line number Diff line
@@ -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

fs/resctrl/internal.h

+4 −0
Original line number Diff line number Diff line
@@ -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);

fs/resctrl/monitor.c

+30 −0
Original line number Diff line number Diff line
@@ -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.

 *

fs/resctrl/rdtgroup.c

+8 −1
Original line number Diff line number Diff line
@@ -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,