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Subject: [PATCH v6 7/8] x86/resctrl: Introduce "-o debug" mount option
From:   Babu Moger <babu.moger@amd.com>
To:     <corbet@lwn.net>, <reinette.chatre@intel.com>,
        <tglx@linutronix.de>, <mingo@redhat.com>, <bp@alien8.de>
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Date:   Wed, 19 Jul 2023 18:22:19 -0500
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Add "-o debug" option to mount resctrl filesystem in debug mode. This=0A=
option is used for adding extra files to help resctrl debugging.=0A=
=0A=
Signed-off-by: Babu Moger <babu.moger@amd.com>=0A=
---=0A=
 Documentation/arch/x86/resctrl.rst     |    5 ++++-=0A=
 arch/x86/kernel/cpu/resctrl/internal.h |    2 ++=0A=
 arch/x86/kernel/cpu/resctrl/rdtgroup.c |   20 ++++++++++++++++++++=0A=
 3 files changed, 26 insertions(+), 1 deletion(-)=0A=
=0A=
diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/re=
sctrl.rst=0A=
index af234681756e..5a2346d2c561 100644=0A=
--- a/Documentation/arch/x86/resctrl.rst=0A=
+++ b/Documentation/arch/x86/resctrl.rst=0A=
@@ -35,7 +35,7 @@ about the feature from resctrl's info directory.=0A=
 =0A=
 To use the feature mount the file system::=0A=
 =0A=
- # mount -t resctrl resctrl [-o cdp[,cdpl2][,mba_MBps]] /sys/fs/resctrl=0A=
+ # mount -t resctrl resctrl [-o cdp[,cdpl2][,mba_MBps][,debug]] /sys/fs/re=
sctrl=0A=
 =0A=
 mount options are:=0A=
 =0A=
@@ -46,6 +46,9 @@ mount options are:=0A=
 "mba_MBps":=0A=
 	Enable the MBA Software Controller(mba_sc) to specify MBA=0A=
 	bandwidth in MBps=0A=
+"debug":=0A=
+	Make debug files accessible. Available debug files are annotated with=0A=
+	"Available only with debug option".=0A=
 =0A=
 L2 and L3 CDP are controlled separately.=0A=
 =0A=
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/r=
esctrl/internal.h=0A=
index 885b656d1088..5bc18accb887 100644=0A=
--- a/arch/x86/kernel/cpu/resctrl/internal.h=0A=
+++ b/arch/x86/kernel/cpu/resctrl/internal.h=0A=
@@ -59,6 +59,7 @@ struct rdt_fs_context {=0A=
 	bool				enable_cdpl2;=0A=
 	bool				enable_cdpl3;=0A=
 	bool				enable_mba_mbps;=0A=
+	bool				enable_debug;=0A=
 };=0A=
 =0A=
 static inline struct rdt_fs_context *rdt_fc2context(struct fs_context *fc)=
=0A=
@@ -296,6 +297,7 @@ struct rdtgroup {=0A=
 #define RFTYPE_TOP			BIT(6)=0A=
 #define RFTYPE_RES_CACHE		BIT(8)=0A=
 #define RFTYPE_RES_MB			BIT(9)=0A=
+#define RFTYPE_DEBUG			BIT(10)=0A=
 #define RFTYPE_CTRL_INFO		(RFTYPE_INFO | RFTYPE_CTRL)=0A=
 #define RFTYPE_MON_INFO			(RFTYPE_INFO | RFTYPE_MON)=0A=
 #define RFTYPE_TOP_INFO			(RFTYPE_INFO | RFTYPE_TOP)=0A=
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/r=
esctrl/rdtgroup.c=0A=
index e0570bce76a2..058c1dedb2d7 100644=0A=
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c=0A=
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c=0A=
@@ -56,6 +56,8 @@ static char last_cmd_status_buf[512];=0A=
 =0A=
 struct dentry *debugfs_resctrl;=0A=
 =0A=
+static bool resctrl_debug;=0A=
+=0A=
 void rdt_last_cmd_clear(void)=0A=
 {=0A=
 	lockdep_assert_held(&rdtgroup_mutex);=0A=
@@ -1871,6 +1873,9 @@ static int rdtgroup_add_files(struct kernfs_node *kn,=
 unsigned long fflags)=0A=
 =0A=
 	lockdep_assert_held(&rdtgroup_mutex);=0A=
 =0A=
+	if (resctrl_debug)=0A=
+		fflags |=3D RFTYPE_DEBUG;=0A=
+=0A=
 	for (rft =3D rfts; rft < rfts + len; rft++) {=0A=
 		if (rft->fflags && ((fflags & rft->fflags) =3D=3D rft->fflags)) {=0A=
 			ret =3D rdtgroup_add_file(kn, rft);=0A=
@@ -2399,6 +2404,9 @@ static int rdt_enable_ctx(struct rdt_fs_context *ctx)=
=0A=
 			goto out_cdpl3;=0A=
 	}=0A=
 =0A=
+	if (ctx->enable_debug)=0A=
+		resctrl_debug =3D true;=0A=
+=0A=
 	return 0;=0A=
 =0A=
 out_cdpl3:=0A=
@@ -2591,6 +2599,8 @@ static int rdt_get_tree(struct fs_context *fc)=0A=
 out_schemata_free:=0A=
 	schemata_list_destroy();=0A=
 out_ctx:=0A=
+	if (ctx->enable_debug)=0A=
+		resctrl_debug =3D false;=0A=
 	if (ctx->enable_mba_mbps)=0A=
 		set_mba_sc(false);=0A=
 	cdp_disable_all();=0A=
@@ -2608,6 +2618,7 @@ enum rdt_param {=0A=
 	Opt_cdp,=0A=
 	Opt_cdpl2,=0A=
 	Opt_mba_mbps,=0A=
+	Opt_debug,=0A=
 	nr__rdt_params=0A=
 };=0A=
 =0A=
@@ -2615,6 +2626,7 @@ static const struct fs_parameter_spec rdt_fs_paramete=
rs[] =3D {=0A=
 	fsparam_flag("cdp",		Opt_cdp),=0A=
 	fsparam_flag("cdpl2",		Opt_cdpl2),=0A=
 	fsparam_flag("mba_MBps",	Opt_mba_mbps),=0A=
+	fsparam_flag("debug",		Opt_debug),=0A=
 	{}=0A=
 };=0A=
 =0A=
@@ -2640,6 +2652,9 @@ static int rdt_parse_param(struct fs_context *fc, str=
uct fs_parameter *param)=0A=
 			return -EINVAL;=0A=
 		ctx->enable_mba_mbps =3D true;=0A=
 		return 0;=0A=
+	case Opt_debug:=0A=
+		ctx->enable_debug =3D true;=0A=
+		return 0;=0A=
 	}=0A=
 =0A=
 	return -EINVAL;=0A=
@@ -2829,6 +2844,8 @@ static void rdt_kill_sb(struct super_block *sb)=0A=
 =0A=
 	set_mba_sc(false);=0A=
 =0A=
+	resctrl_debug =3D false;=0A=
+=0A=
 	/*Put everything back to default values. */=0A=
 	for_each_alloc_capable_rdt_resource(r)=0A=
 		reset_all_ctrls(r);=0A=
@@ -3710,6 +3727,9 @@ static int rdtgroup_show_options(struct seq_file *seq=
, struct kernfs_root *kf)=0A=
 	if (is_mba_sc(&rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl))=0A=
 		seq_puts(seq, ",mba_MBps");=0A=
 =0A=
+	if (resctrl_debug)=0A=
+		seq_puts(seq, ",debug");=0A=
+=0A=
 	return 0;=0A=
 }=0A=
 =0A=
=0A=