linux-kernel - [PATCH v3 07/10] x86/resctrl: Add sysfs interface files to read/write event configuration

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Date:   Mon, 22 Aug 2022 08:43:53 -0500
From:   Babu Moger <babu.moger@....com>
To:     <fenghua.yu@...el.com>, <reinette.chatre@...el.com>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>
CC:     <eranian@...gle.com>, <dave.hansen@...ux.intel.com>,
        <x86@...nel.org>, <hpa@...or.com>, <corbet@....net>,
        <hpa@...or.com>, <linux-kernel@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <bagasdotme@...il.com>
Subject: [PATCH v3 07/10] x86/resctrl: Add sysfs interface files to read/write
 event configuration

Add two new sysfs files to read/write the event configuration if
the feature Bandwidth Monitoring Event Configuration (BMEC) is
supported. The file mbm_local_config is for the configuration
of the event mbm_local_bytes and the file mbm_total_config is
for the configuration of mbm_total_bytes.

$ls /sys/fs/resctrl/mon_data/mon_L3_00/mbm_local*
/sys/fs/resctrl/mon_data/mon_L3_00/mbm_local_bytes
/sys/fs/resctrl/mon_data/mon_L3_00/mbm_local_config

$ls /sys/fs/resctrl/mon_data/mon_L3_00/mbm_total*
/sys/fs/resctrl/mon_data/mon_L3_00/mbm_total_bytes
/sys/fs/resctrl/mon_data/mon_L3_00/mbm_total_config

Signed-off-by: Babu Moger <babu.moger@....com>
Reviewed-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/cpu/resctrl/internal.h |    3 +++
 arch/x86/kernel/cpu/resctrl/monitor.c  |    2 ++
 arch/x86/kernel/cpu/resctrl/rdtgroup.c |   32 ++++++++++++++++++++++++++++++++
 3 files changed, 37 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index c049a274383c..fc725f5e9024 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -72,11 +72,13 @@ DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
  * struct mon_evt - Entry in the event list of a resource
  * @evtid:		event id
  * @name:		name of the event
+ * @config:	current configuration
  * @list:		entry in &rdt_resource->evt_list
  */
 struct mon_evt {
 	u32			evtid;
 	char			*name;
+	char			*config;
 	struct list_head	list;
 };
 
@@ -95,6 +97,7 @@ union mon_data_bits {
 		unsigned int rid	: 10;
 		unsigned int evtid	: 8;
 		unsigned int domid	: 14;
+		unsigned int mon_config : 32;
 	} u;
 };
 
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index b9de417dac1c..3f900241dbab 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -656,11 +656,13 @@ static struct mon_evt llc_occupancy_event = {
 static struct mon_evt mbm_total_event = {
 	.name		= "mbm_total_bytes",
 	.evtid		= QOS_L3_MBM_TOTAL_EVENT_ID,
+	.config 	= "mbm_total_config",
 };
 
 static struct mon_evt mbm_local_event = {
 	.name		= "mbm_local_bytes",
 	.evtid		= QOS_L3_MBM_LOCAL_EVENT_ID,
+	.config 	= "mbm_local_config",
 };
 
 /*
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 855483b297a8..30d2182d4fda 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -254,6 +254,10 @@ static const struct kernfs_ops kf_mondata_ops = {
 	.seq_show		= rdtgroup_mondata_show,
 };
 
+static const struct kernfs_ops kf_mondata_config_ops = {
+	.atomic_write_len       = PAGE_SIZE,
+};
+
 static bool is_cpu_list(struct kernfs_open_file *of)
 {
 	struct rftype *rft = of->kn->priv;
@@ -2534,6 +2538,25 @@ void rmdir_mondata_subdir_allrdtgrp(struct rdt_resource *r, unsigned int dom_id)
 	}
 }
 
+static int mon_config_addfile(struct kernfs_node *parent_kn, const char *name,
+			      void *priv)
+{
+	struct kernfs_node *kn;
+	int ret = 0;
+
+	kn = __kernfs_create_file(parent_kn, name, 0644,
+			GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, 0,
+			&kf_mondata_config_ops, priv, NULL, NULL);
+	if (IS_ERR(kn))
+		return PTR_ERR(kn);
+
+	ret = rdtgroup_kn_set_ugid(kn);
+	if (ret)
+		kernfs_remove(kn);
+
+	return ret;
+}
+
 static int mkdir_mondata_subdir(struct kernfs_node *parent_kn,
 				struct rdt_domain *d,
 				struct rdt_resource *r, struct rdtgroup *prgrp)
@@ -2568,6 +2591,15 @@ static int mkdir_mondata_subdir(struct kernfs_node *parent_kn,
 		if (ret)
 			goto out_destroy;
 
+		/* Create the sysfs event configuration files */
+		if (r->mon_configurable &&
+		    (mevt->evtid == QOS_L3_MBM_TOTAL_EVENT_ID ||
+		     mevt->evtid == QOS_L3_MBM_LOCAL_EVENT_ID)) {
+			ret = mon_config_addfile(kn, mevt->config, priv.priv);
+			if (ret)
+				goto out_destroy;
+		}
+
 		if (is_mbm_event(mevt->evtid))
 			mon_event_read(&rr, r, d, prgrp, mevt->evtid, true);
 	}