x86/resctrl: Prepare for per-CTRL_MON group mba_MBps control

Resctrl uses local memory bandwidth event as input to the feedback loop when
the mba_MBps mount option is used. This means that this mount option cannot be
used on systems that only support monitoring of total bandwidth.

Prepare to allow users to choose the input event independently for each
CTRL_MON group by adding a global variable "mba_mbps_default_event" used to
set the default event for each CTRL_MON group, and a new field
"mba_mbps_event" in struct rdtgroup to track which event is used for each
CTRL_MON group.

Notes:

1) Both of these are only used when the user mounts the filesystem with the
   "mba_MBps" option.
2) Only check for support of local bandwidth event when initializing
   mba_mbps_default_event. Support for total bandwidth event can be added
   after other routines in resctrl have been updated to handle total bandwidth
   event.

  [ bp: Move mba_mbps_default_event extern into the arch header. ]

Signed-off-by: Tony Luck <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Reviewed-by: Reinette Chatre <[email protected]>
Tested-by: Babu Moger <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: aegl

arch/x86/kernel/cpu/resctrl/core.c

@@ -963,6 +963,9 @@ static __init bool get_rdt_mon_resources(void)
 	if (!rdt_mon_features)
 		return false;
 
+	if (is_mbm_local_enabled())
+		mba_mbps_default_event = QOS_L3_MBM_LOCAL_EVENT_ID;
+
 	return !rdt_get_mon_l3_config(r);
 }
 

arch/x86/kernel/cpu/resctrl/internal.h

@@ -283,6 +283,7 @@ struct pseudo_lock_region {
  *				monitor only or ctrl_mon group
  * @mon:			mongroup related data
  * @mode:			mode of resource group
+ * @mba_mbps_event:		input monitoring event id when mba_sc is enabled
  * @plr:			pseudo-locked region
  */
 struct rdtgroup {
@@ -295,6 +296,7 @@ struct rdtgroup {
 	enum rdt_group_type		type;
 	struct mongroup			mon;
 	enum rdtgrp_mode		mode;
+	enum resctrl_event_id		mba_mbps_event;
 	struct pseudo_lock_region	*plr;
 };
 
@@ -508,6 +510,7 @@ extern struct mutex rdtgroup_mutex;
 extern struct rdt_hw_resource rdt_resources_all[];
 extern struct rdtgroup rdtgroup_default;
 extern struct dentry *debugfs_resctrl;
+extern enum resctrl_event_id mba_mbps_default_event;
 
 enum resctrl_res_level {
 	RDT_RESOURCE_L3,
@@ -651,5 +654,4 @@ void resctrl_file_fflags_init(const char *config, unsigned long fflags);
 void rdt_staged_configs_clear(void);
 bool closid_allocated(unsigned int closid);
 int resctrl_find_cleanest_closid(void);
-
 #endif /* _ASM_X86_RESCTRL_INTERNAL_H */

arch/x86/kernel/cpu/resctrl/rdtgroup.c

@@ -65,6 +65,15 @@ static void rdtgroup_destroy_root(void);
 
 struct dentry *debugfs_resctrl;
 
+/*
+ * Memory bandwidth monitoring event to use for the default CTRL_MON group
+ * and each new CTRL_MON group created by the user.  Only relevant when
+ * the filesystem is mounted with the "mba_MBps" option so it does not
+ * matter that it remains uninitialized on systems that do not support
+ * the "mba_MBps" option.
+ */
+enum resctrl_event_id mba_mbps_default_event;
+
 static bool resctrl_debug;
 
 void rdt_last_cmd_clear(void)
@@ -2353,6 +2362,8 @@ static int set_mba_sc(bool mba_sc)
 
 	r->membw.mba_sc = mba_sc;
 
+	rdtgroup_default.mba_mbps_event = mba_mbps_default_event;
+
 	list_for_each_entry(d, &r->ctrl_domains, hdr.list) {
 		for (i = 0; i < num_closid; i++)
 			d->mbps_val[i] = MBA_MAX_MBPS;
@@ -3611,6 +3622,8 @@ static int rdtgroup_mkdir_ctrl_mon(struct kernfs_node *parent_kn,
 			rdt_last_cmd_puts("kernfs subdir error\n");
 			goto out_del_list;
 		}
+		if (is_mba_sc(NULL))
+			rdtgrp->mba_mbps_event = mba_mbps_default_event;
 	}
 
 	goto out_unlock;