[PATCH v13 10/10] x86/resctrl: Display RMID of resource group

[Babu Moger]

In x86, hardware uses RMID to identify a monitoring group. When a user
creates a monitor group these details are not visible. These details
can help resctrl debugging.

Add RMID(mon_hw_id) to the monitor groups display in resctrl interface.
Users can see these details when resctrl is mounted with "-o debug" option.

Add RFTYPE_MON_BASE that complements existing RFTYPE_CTRL_BASE and
represents files belonging to monitoring groups.

Other architectures do not use "RMID". Use the name mon_hw_id to refer
to "RMID" in an effort to keep the naming generic.

For example:
 $cat /sys/fs/resctrl/mon_groups/mon_grp1/mon_hw_id
 3

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
Tested-by: Peter Newman <peternewman@xxxxxxxxxx>
Reviewed-by: Peter Newman <peternewman@xxxxxxxxxx>
Tested-by: Tan Shaopeng <tan.shaopeng@xxxxxxxxxxxxxx>
Reviewed-by: Tan Shaopeng <tan.shaopeng@xxxxxxxxxxxxxx>
Reviewed-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
---
v13: Minor commit message update. (Reinette).

v12: Moved the comments from arch/x86/kernel/cpu/resctrl/internal.h
     to Documentation/arch/x86/resctrl.rst. (Boris)
     Moved RFTYPE_MON_BASE definition here where it is being used. (Boris)
---
 Documentation/arch/x86/resctrl.rst     | 12 ++++++++++++
 arch/x86/kernel/cpu/resctrl/internal.h |  1 +
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 23 +++++++++++++++++++++++
 3 files changed, 36 insertions(+)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 07225d9c0b0f..d1538b480b22 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -376,6 +376,10 @@ When monitoring is enabled all MON groups will also contain:
 	the sum for all tasks in the CTRL_MON group and all tasks in
 	MON groups. Please see example section for more details on usage.
 
+"mon_hw_id":
+	Available only with debug option. The identifier used by hardware
+	for the monitor group. On x86 this is the RMID.
+
 RESCTRL filesystem implementation notes
 =======================================
 RESCTRL filesystem has two main components
@@ -440,6 +444,14 @@ RESCTRL filesystem has two main components
 		-> RFTYPE_CTRL (Files for CTRL group)
 		   Files: mode, schemata, size
 
+		-> RFTYPE_MON (Files for MON group)
+
+			-> RFTYPE_DEBUG (Files to help resctrl debugging)
+			    File: mon_hw_id
+
+		-> RFTYPE_CTRL (Files for CTRL group)
+		    Files: mode, schemata, size
+
 			-> RFTYPE_DEBUG (Files to help resctrl debugging)
 			   File: ctrl_hw_id
 
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index b816b902b5c0..a4f1aa15f0a2 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -254,6 +254,7 @@ struct rdtgroup {
 #define RFTYPE_MON_INFO			(RFTYPE_INFO | RFTYPE_MON)
 #define RFTYPE_TOP_INFO			(RFTYPE_INFO | RFTYPE_TOP)
 #define RFTYPE_CTRL_BASE		(RFTYPE_BASE | RFTYPE_CTRL)
+#define RFTYPE_MON_BASE			(RFTYPE_BASE | RFTYPE_MON)
 
 /* List of all resource groups */
 extern struct list_head rdt_all_groups;
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 5f6d6ba63a2e..69a1de92384a 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -795,6 +795,22 @@ static int rdtgroup_closid_show(struct kernfs_open_file *of,
 	return ret;
 }
 
+static int rdtgroup_rmid_show(struct kernfs_open_file *of,
+			      struct seq_file *s, void *v)
+{
+	struct rdtgroup *rdtgrp;
+	int ret = 0;
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	if (rdtgrp)
+		seq_printf(s, "%u\n", rdtgrp->mon.rmid);
+	else
+		ret = -ENOENT;
+	rdtgroup_kn_unlock(of->kn);
+
+	return ret;
+}
+
 #ifdef CONFIG_PROC_CPU_RESCTRL
 
 /*
@@ -1867,6 +1883,13 @@ static struct rftype res_common_files[] = {
 		.seq_show	= rdtgroup_tasks_show,
 		.fflags		= RFTYPE_BASE,
 	},
+	{
+		.name		= "mon_hw_id",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= rdtgroup_rmid_show,
+		.fflags		= RFTYPE_MON_BASE | RFTYPE_DEBUG,
+	},
 	{
 		.name		= "schemata",
 		.mode		= 0644,
-- 
2.34.1