[PATCH v17 13/33] fs/resctrl: Introduce interface to display number of free MBM counters

[Babu Moger <babu.moger@amd.com>]

Introduce the "available_mbm_cntrs" resctrl file to display the number of
counters available for assignment in each domain when "mbm_event" mode is
enabled.

Signed-off-by: Babu Moger <babu.moger@amd.com>
---
v17: Moved resctrl_available_mbm_cntrs_show() to fs/resctrl/monitor.c.
     Removed the Reviewed-by tag.

v16: Added Reviewed-by tag.

v15: Minor changelog text update.
     Minor resctrl.rst text update and corrected the error text in
     resctrl_available_mbm_cntrs_show().
     Changed the goto label to out_unlock for consistency.

v14: Minor changelog update.
     Changed subject line to fs/resctrl.

v13: Resolved conflicts caused by the recent FS/ARCH code restructure.
     The files monitor.c and rdtgroup.c file has now been split between
     the FS and ARCH directories.

v12: Minor change to change log.
     Updated the documentation text with an example.
     Replaced seq_puts(s, ";") with seq_putc(s, ';');
     Added missing rdt_last_cmd_clear() in resctrl_available_mbm_cntrs_show().

v11: Rename rdtgroup_available_mbm_cntrs_show() to resctrl_available_mbm_cntrs_show().
     Few minor text changes.

v10: Patch changed to handle the counters at domain level.
     https://lore.kernel.org/lkml/CALPaoCj+zWq1vkHVbXYP0znJbe6Ke3PXPWjtri5AFgD9cQDCUg@mail.gmail.com/
     So, display logic also changed now.

v9: New patch
---
 Documentation/filesystems/resctrl.rst | 11 +++++++
 fs/resctrl/internal.h                 |  3 ++
 fs/resctrl/monitor.c                  | 44 +++++++++++++++++++++++++++
 fs/resctrl/rdtgroup.c                 |  6 ++++
 4 files changed, 64 insertions(+)

diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 4eb27530be6f..446736dbd97f 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -299,6 +299,17 @@ with the following files:
 	  # cat /sys/fs/resctrl/info/L3_MON/num_mbm_cntrs
 	  0=32;1=32
 
+"available_mbm_cntrs":
+	The number of counters available for assignment in each domain when mbm_event
+	mode is enabled on the system.
+
+	For example, on a system with 30 available [hardware] assignable counters
+	in each of its L3 domains:
+	::
+
+	  # cat /sys/fs/resctrl/info/L3_MON/available_mbm_cntrs
+	  0=30;1=30
+
 "max_threshold_occupancy":
 		Read/write file provides the largest value (in
 		bytes) at which a previously used LLC_occupancy
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index e4d7aa1a8fd1..35a8bad8ca75 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -388,6 +388,9 @@ int resctrl_mbm_assign_mode_show(struct kernfs_open_file *of, struct seq_file *s
 
 int resctrl_num_mbm_cntrs_show(struct kernfs_open_file *of, struct seq_file *s, void *v);
 
+int resctrl_available_mbm_cntrs_show(struct kernfs_open_file *of, struct seq_file *s,
+				     void *v);
+
 #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 667770ecfd78..4185f2a4ba89 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -938,6 +938,48 @@ int resctrl_num_mbm_cntrs_show(struct kernfs_open_file *of,
 	return 0;
 }
 
+int resctrl_available_mbm_cntrs_show(struct kernfs_open_file *of,
+				     struct seq_file *s, void *v)
+{
+	struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
+	struct rdt_mon_domain *dom;
+	bool sep = false;
+	u32 cntrs, i;
+	int ret = 0;
+
+	cpus_read_lock();
+	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;
+	}
+
+	list_for_each_entry(dom, &r->mon_domains, hdr.list) {
+		if (sep)
+			seq_putc(s, ';');
+
+		cntrs = 0;
+		for (i = 0; i < r->mon.num_mbm_cntrs; i++) {
+			if (!dom->cntr_cfg[i].rdtgrp)
+				cntrs++;
+		}
+
+		seq_printf(s, "%d=%u", dom->hdr.id, cntrs);
+		sep = true;
+	}
+	seq_putc(s, '\n');
+
+out_unlock:
+	mutex_unlock(&rdtgroup_mutex);
+	cpus_read_unlock();
+
+	return ret;
+}
+
 /**
  * resctrl_mon_resource_init() - Initialise global monitoring structures.
  *
@@ -985,6 +1027,8 @@ int resctrl_mon_resource_init(void)
 			resctrl_enable_mon_event(QOS_L3_MBM_LOCAL_EVENT_ID);
 		resctrl_file_fflags_init("num_mbm_cntrs",
 					 RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
+		resctrl_file_fflags_init("available_mbm_cntrs",
+					 RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
 	}
 
 	return 0;
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index ce1c894dab18..8eaad45b28ea 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1822,6 +1822,12 @@ static struct rftype res_common_files[] = {
 		.seq_show	= rdt_mon_features_show,
 		.fflags		= RFTYPE_MON_INFO,
 	},
+	{
+		.name		= "available_mbm_cntrs",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= resctrl_available_mbm_cntrs_show,
+	},
 	{
 		.name		= "num_rmids",
 		.mode		= 0444,
-- 
2.34.1