[PATCH v9 8/9] x86/resctrl: Display CLOSID for resource group

[Babu Moger]

In x86, hardware uses CLOSID to identify a control group. When a user
creates a control group this information is not visible to the user.
It can help resctrl debugging.

Add CLOSID(ctrl_hw_id) to the control groups display in resctrl
interface. Users can see this detail when resctrl is mounted with
"-o debug" option.

Other architectures do not use "CLOSID". Use the names ctrl_hw_id
to refer to "CLOSID" in an effort to keep the naming generic.

For example:
 $cat /sys/fs/resctrl/ctrl_grp1/ctrl_hw_id
 1

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
 Documentation/arch/x86/resctrl.rst     |  4 ++++
 arch/x86/kernel/cpu/resctrl/internal.h |  3 +++
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 23 +++++++++++++++++++++++
 3 files changed, 30 insertions(+)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 28d35aaa74b4..54691c8b832d 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -352,6 +352,10 @@ When control is enabled all CTRL_MON groups will also contain:
 	file. On successful pseudo-locked region creation the mode will
 	automatically change to "pseudo-locked".
 
+"ctrl_hw_id":
+	Available only with debug option. The identifier used by hardware
+	for the control group. On x86 this is the CLOSID.
+
 When monitoring is enabled all MON groups will also contain:
 
 "mon_data":
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 38b99a21ccd8..ccdbed615d41 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -299,6 +299,9 @@ struct rdtgroup {
  *		--> RFTYPE_CTRL (Files only for CTRL group)
  *		    Files: mode, schemata, size
  *
+ *			--> RFTYPE_DEBUG (Files to help resctrl debugging)
+ *			    File: ctrl_hw_id
+ *
  */
 #define RFTYPE_INFO			BIT(0)
 #define RFTYPE_BASE			BIT(1)
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 67b315f3a26c..8be0fb323ad3 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -779,6 +779,22 @@ static int rdtgroup_tasks_show(struct kernfs_open_file *of,
 	return ret;
 }
 
+static int rdtgroup_closid_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->closid);
+	else
+		ret = -ENOENT;
+	rdtgroup_kn_unlock(of->kn);
+
+	return ret;
+}
+
 #ifdef CONFIG_PROC_CPU_RESCTRL
 
 /*
@@ -1863,6 +1879,13 @@ static struct rftype res_common_files[] = {
 		.seq_show	= rdtgroup_size_show,
 		.fflags		= RFTYPE_CTRL_BASE,
 	},
+	{
+		.name		= "ctrl_hw_id",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= rdtgroup_closid_show,
+		.fflags		= RFTYPE_CTRL_BASE | RFTYPE_DEBUG,
+	},
 
 };
 
-- 
2.34.1