fs/resctrl: Introduce mbm_assign_on_mkdir to enable assignments on mkdir

The "mbm_event" counter assignment mode allows users to assign a hardware
counter to an RMID, event pair and monitor the bandwidth as long as it is
assigned.

Introduce a user-configurable option that determines if a counter will
automatically be assigned to an RMID, event pair when its associated
monitor group is created via mkdir. Accessible when "mbm_event" counter
assignment mode is enabled.

Suggested-by: Peter Newman <peternewman@google.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com

3 files changed, 66 insertions, 0 deletions

diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index 90d3e4ab335b..66c677c1b858 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -410,6 +410,12 @@ int event_filter_show(struct kernfs_open_file *of, struct seq_file *seq, void *v
 ssize_t event_filter_write(struct kernfs_open_file *of, char *buf, size_t nbytes,
 			   loff_t off);
 
+int resctrl_mbm_assign_on_mkdir_show(struct kernfs_open_file *of,
+				     struct seq_file *s, void *v);
+
+ssize_t resctrl_mbm_assign_on_mkdir_write(struct kernfs_open_file *of, char *buf,
+					  size_t nbytes, loff_t off);
+
 #ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
 int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);
 
diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index ccb9726bba54..deca9535fbbb 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -1027,6 +1027,57 @@ out_unlock:
 	return ret;
 }
 
+int resctrl_mbm_assign_on_mkdir_show(struct kernfs_open_file *of, struct seq_file *s,
+				     void *v)
+{
+	struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
+	int ret = 0;
+
+	mutex_lock(&rdtgroup_mutex);
+	rdt_last_cmd_clear();
+
+	if (!resctrl_arch_mbm_cntr_assign_enabled(r)) {
+		rdt_last_cmd_puts("mbm_event counter assignment mode is not enabled\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	seq_printf(s, "%u\n", r->mon.mbm_assign_on_mkdir);
+
+out_unlock:
+	mutex_unlock(&rdtgroup_mutex);
+
+	return ret;
+}
+
+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 = rdt_kn_parent_priv(of->kn);
+	bool value;
+	int ret;
+
+	ret = kstrtobool(buf, &value);
+	if (ret)
+		return ret;
+
+	mutex_lock(&rdtgroup_mutex);
+	rdt_last_cmd_clear();
+
+	if (!resctrl_arch_mbm_cntr_assign_enabled(r)) {
+		rdt_last_cmd_puts("mbm_event counter assignment mode is not enabled\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	r->mon.mbm_assign_on_mkdir = value;
+
+out_unlock:
+	mutex_unlock(&rdtgroup_mutex);
+
+	return ret ?: nbytes;
+}
+
 /*
  * rdtgroup_assign_cntr() - Assign/unassign the counter ID for the event, RMID
  * pair in the domain.
@@ -1457,6 +1508,8 @@ int resctrl_mon_resource_init(void)
 		resctrl_file_fflags_init("available_mbm_cntrs",
 					 RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
 		resctrl_file_fflags_init("event_filter", RFTYPE_ASSIGN_CONFIG);
+		resctrl_file_fflags_init("mbm_assign_on_mkdir", RFTYPE_MON_INFO |
+					 RFTYPE_RES_CACHE);
 	}
 
 	return 0;
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index e90bc808fe53..c7ea42c2a3c2 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1809,6 +1809,13 @@ static struct rftype res_common_files[] = {
 		.fflags		= RFTYPE_TOP_INFO,
 	},
 	{
+		.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		= "num_closids",
 		.mode		= 0444,
 		.kf_ops		= &rdtgroup_kf_single_ops,