[PATCH v12 11/26] x86/resctrl: Introduce interface to display number of free MBM counters

Babu Moger
2025-04-04T00:20:30Z

Provide the interface to display the number of monitoring counters
available for assignment in each domain when mbm_cntr_assign mode is
enabled.

Signed-off-by: Babu Moger <babu.moger@amd.com>
---
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/arch/x86/resctrl.rst | 11 ++++++
arch/x86/kernel/cpu/resctrl/monitor.c | 4 ++-
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 48 ++++++++++++++++++++++++++
3 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 35d908befdfb..44128fbda4fe 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -295,6 +295,17 @@ with the following files:
# cat /sys/fs/resctrl/info/L3_MON/num_mbm_cntrs
0=32;1=32

+"available_mbm_cntrs":
+ The number of monitoring counters available for assignment in each
+ domain when mbm_cntr_assign mode is enabled on the system.
+
+ For example, on a system with 30 available [hardware] monitoring 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/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 028b49878ad0..8a88ac29d57d 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -1234,8 +1234,10 @@ int __init resctrl_mon_resource_init(void)
else if (resctrl_arch_is_mbm_total_enabled())
mba_mbps_default_event = QOS_L3_MBM_TOTAL_EVENT_ID;

- if (r->mon.mbm_cntr_assignable)
+ if (r->mon.mbm_cntr_assignable) {
resctrl_file_fflags_init("num_mbm_cntrs", RFTYPE_MON_INFO);
+ resctrl_file_fflags_init("available_mbm_cntrs", RFTYPE_MON_INFO);
+ }

return 0;
}
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index cb7a8a2de3ff..07792b45bd63 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -936,6 +936,48 @@ static int resctrl_num_mbm_cntrs_show(struct kernfs_open_file *of,
return 0;
}

+static int resctrl_available_mbm_cntrs_show(struct kernfs_open_file *of,
+ struct seq_file *s, void *v)
+{
+ struct rdt_resource *r = of->kn->parent->priv;
+ 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_cntr_assign mode is not enabled\n");
+ ret = -EINVAL;
+ goto unlock_cntrs_show;
+ }
+
+ 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_puts(s, "\n");
+
+unlock_cntrs_show:
+ mutex_unlock(&rdtgroup_mutex);
+ cpus_read_unlock();
+
+ return ret;
+}
+
#ifdef CONFIG_PROC_CPU_RESCTRL

/*
@@ -1975,6 +2017,12 @@ static struct rftype res_common_files[] = {
.kf_ops = &rdtgroup_kf_single_ops,
.seq_show = resctrl_num_mbm_cntrs_show,
},
+ {
+ .name = "available_mbm_cntrs",
+ .mode = 0444,
+ .kf_ops = &rdtgroup_kf_single_ops,
+ .seq_show = resctrl_available_mbm_cntrs_show,
+ },
{
.name = "cpus",
.mode = 0644,
--
2.34.1