[tip: x86/cache] fs/resctrl: Introduce interface to display number of free MBM counters

["tip-bot2 for Babu Moger" <tip-bot2@linutronix.de>]

The following commit has been merged into the x86/cache branch of tip:

Commit-ID:     16ff6b038fb3b64aa033efdc95d673239610e1a6
Gitweb:        https://git.kernel.org/tip/16ff6b038fb3b64aa033efdc95d673239610e1a6
Author:        Babu Moger <babu.moger@amd.com>
AuthorDate:    Fri, 05 Sep 2025 16:34:12 -05:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Mon, 15 Sep 2025 12:16:11 +02:00

fs/resctrl: Introduce interface to display number of free MBM counters

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>
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
---
 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 4eb2753..446736d 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 7a12187..4f372e8 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 112979e..1fa82a6 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -936,6 +936,48 @@ 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.
  *
@@ -983,6 +1025,8 @@ 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 61f7b68..2e1d0a2 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1823,6 +1823,12 @@ static struct rftype res_common_files[] = {
 		.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,
 		.kf_ops		= &rdtgroup_kf_single_ops,