[PATCH v5 5/8] x86/resctrl: Introduce "-o debug" mount option

[Babu Moger]

Add "-o debug" option to mount resctrl filesystem in debug mode.
This option can be used for adding extra files to help debug
resctrl issues.

For example, hardware uses CLOSID and RMIDs to control and monitor
resctrl resources. These numbers are not visible to the user. These
details can help to debug issues. Debug option provides a method to
add these files to resctrl.

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
 Documentation/arch/x86/resctrl.rst     |    3 +++
 arch/x86/kernel/cpu/resctrl/internal.h |    1 +
 arch/x86/kernel/cpu/resctrl/rdtgroup.c |   15 +++++++++++++++
 3 files changed, 19 insertions(+)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 290f01aa3002..afdee4d1f691 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -46,6 +46,9 @@ mount options are:
 "mba_MBps":
 	Enable the MBA Software Controller(mba_sc) to specify MBA
 	bandwidth in MBps
+"debug":
+	Make debug files accessible. Available debug files are annotated with
+	"Available only with debug option".
 
 L2 and L3 CDP are controlled separately.
 
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index c20cd6acb7a3..c07c6517d856 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -59,6 +59,7 @@ struct rdt_fs_context {
 	bool				enable_cdpl2;
 	bool				enable_cdpl3;
 	bool				enable_mba_mbps;
+	bool				enable_debug;
 };
 
 static inline struct rdt_fs_context *rdt_fc2context(struct fs_context *fc)
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index baed20b2d788..be91dea5f927 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -56,6 +56,8 @@ static char last_cmd_status_buf[512];
 
 struct dentry *debugfs_resctrl;
 
+static bool resctrl_debug;
+
 void rdt_last_cmd_clear(void)
 {
 	lockdep_assert_held(&rdtgroup_mutex);
@@ -2368,6 +2370,9 @@ static int rdt_enable_ctx(struct rdt_fs_context *ctx)
 	if (!ret && ctx->enable_mba_mbps)
 		ret = set_mba_sc(true);
 
+	if (!ret && ctx->enable_debug)
+		resctrl_debug = true;
+
 	return ret;
 }
 
@@ -2556,6 +2561,7 @@ enum rdt_param {
 	Opt_cdp,
 	Opt_cdpl2,
 	Opt_mba_mbps,
+	Opt_debug,
 	nr__rdt_params
 };
 
@@ -2563,6 +2569,7 @@ static const struct fs_parameter_spec rdt_fs_parameters[] = {
 	fsparam_flag("cdp",		Opt_cdp),
 	fsparam_flag("cdpl2",		Opt_cdpl2),
 	fsparam_flag("mba_MBps",	Opt_mba_mbps),
+	fsparam_flag("debug",		Opt_debug),
 	{}
 };
 
@@ -2588,6 +2595,9 @@ static int rdt_parse_param(struct fs_context *fc, struct fs_parameter *param)
 			return -EINVAL;
 		ctx->enable_mba_mbps = true;
 		return 0;
+	case Opt_debug:
+		ctx->enable_debug = true;
+		return 0;
 	}
 
 	return -EINVAL;
@@ -2778,6 +2788,8 @@ static void rdt_kill_sb(struct super_block *sb)
 
 	set_mba_sc(false);
 
+	resctrl_debug = false;
+
 	/*Put everything back to default values. */
 	for_each_alloc_capable_rdt_resource(r)
 		reset_all_ctrls(r);
@@ -3530,6 +3542,9 @@ static int rdtgroup_show_options(struct seq_file *seq, struct kernfs_root *kf)
 	if (is_mba_sc(&rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl))
 		seq_puts(seq, ",mba_MBps");
 
+	if (resctrl_debug)
+		seq_puts(seq, ",debug");
+
 	return 0;
 }