[PATCH v12 21/26] x86/resctrl: Introduce mbm_assign_on_mkdir to configure assignments

[Babu Moger]

The mbm_cntr_assign mode provides an option to the user to assign a
counter to an RMID, event pair and monitor the bandwidth as long as
the counter is assigned.

Introduce a configuration option to automatically assign counter IDs
when a resctrl group is created, provided the counters are available.
By default, this option is enabled at boot.

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
v12: New patch. Added after the discussion on the list.
     https://lore.kernel.org/lkml/CALPaoCh8siZKjL_3yvOYGL4cF_n_38KpUFgHVGbQ86nD+Q2_SA@xxxxxxxxxxxxxx/
---
 Documentation/arch/x86/resctrl.rst     | 10 +++++++
 arch/x86/kernel/cpu/resctrl/monitor.c  |  1 +
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 40 ++++++++++++++++++++++++++
 include/linux/resctrl.h                |  2 ++
 4 files changed, 53 insertions(+)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 4e6feba6fb08..a67f09323da0 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -345,6 +345,16 @@ with the following files:
 	    # cat /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_total_bytes/event_filter
 	    local_reads, local_non_temporal_writes
 
+"mbm_assign_on_mkdir":
+	Automatically assign the monitoring counters on resctrl group creation
+	if the counters are available. It is enabled by default on boot and users
+	can disable by writing to the interface.
+	::
+
+	  # echo 0 > /sys/fs/resctrl/info/L3_MON/mbm_assign_on_mkdir
+	  # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_on_mkdir
+	  0
+
 "max_threshold_occupancy":
 		Read/write file provides the largest value (in
 		bytes) at which a previously used LLC_occupancy
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 4525295b1725..ee31dfe2c224 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -1265,6 +1265,7 @@ int __init resctrl_mon_resource_init(void)
 		resctrl_file_fflags_init("num_mbm_cntrs", RFTYPE_MON_INFO);
 		resctrl_file_fflags_init("available_mbm_cntrs", RFTYPE_MON_INFO);
 		resctrl_file_fflags_init("event_filter", RFTYPE_MON_CONFIG);
+		resctrl_file_fflags_init("mbm_assign_on_mkdir", RFTYPE_MON_INFO);
 	}
 
 	return 0;
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 7792455f0b26..592a9dc5b404 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -993,6 +993,39 @@ static int resctrl_available_mbm_cntrs_show(struct kernfs_open_file *of,
 	return ret;
 }
 
+static int resctrl_mbm_assign_on_mkdir_show(struct kernfs_open_file *of,
+					    struct seq_file *s, void *v)
+{
+	struct rdt_resource *r = of->kn->parent->priv;
+
+	seq_printf(s, "%u\n", r->mon.mbm_assign_on_mkdir);
+
+	return 0;
+}
+
+static ssize_t resctrl_mbm_assign_on_mkdir_write(struct kernfs_open_file *of,
+						 char *buf, size_t nbytes, loff_t off)
+{
+	struct rdt_resource *r = of->kn->parent->priv;
+	bool value;
+	int ret;
+
+	ret = kstrtobool(buf, &value);
+	if (ret)
+		return ret;
+
+	cpus_read_lock();
+	mutex_lock(&rdtgroup_mutex);
+	rdt_last_cmd_clear();
+
+	r->mon.mbm_assign_on_mkdir = value;
+
+	mutex_unlock(&rdtgroup_mutex);
+	cpus_read_unlock();
+
+	return ret ?: nbytes;
+}
+
 #ifdef CONFIG_PROC_CPU_RESCTRL
 
 /*
@@ -2176,6 +2209,13 @@ static struct rftype res_common_files[] = {
 		.kf_ops		= &rdtgroup_kf_single_ops,
 		.seq_show	= resctrl_available_mbm_cntrs_show,
 	},
+	{
+		.name		= "mbm_assign_on_mkdir",
+		.mode		= 0644,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= resctrl_mbm_assign_on_mkdir_show,
+		.write		= resctrl_mbm_assign_on_mkdir_write,
+	},
 	{
 		.name		= "cpus",
 		.mode		= 0644,
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 107cb14a0db2..ad3d986c4ea1 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -250,6 +250,7 @@ enum resctrl_schema_fmt {
  *			monitoring events can be configured.
  * @num_mbm_cntrs:	Number of assignable monitoring counters
  * @mbm_cntr_assignable:Is system capable of supporting monitor assignment?
+ * @mbm_assign_on_mkdir:Auto enable monitor assignment on mkdir?
  * @evt_list:		List of monitoring events
  */
 struct resctrl_mon {
@@ -257,6 +258,7 @@ struct resctrl_mon {
 	unsigned int		mbm_cfg_mask;
 	int			num_mbm_cntrs;
 	bool			mbm_cntr_assignable;
+	bool			mbm_assign_on_mkdir;
 	struct list_head	evt_list;
 };
 
-- 
2.34.1