[PATCH v8 08/25] x86/resctrl: Introduce interface to display number of monitoring counters

[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. Number of assignments depend on number of
monitoring counters available.

Provide the interface to display the number of monitoring counters
supported. The interface file 'num_mbm_cntrs' is available when an
architecture supports mbm_cntr_assign mode.

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
v8: Commit message update and documentation update.

v7: Minor commit log text changes.

v6: No changes.

v5: Changed the display name from num_cntrs to num_mbm_cntrs.
    Updated the commit message.
    Moved the patch after mbm_mode is introduced.

v4: Changed the counter name to num_cntrs. And few text changes.

v3: Changed the field name to mbm_assign_cntrs.

v2: Changed the field name to mbm_assignable_counters from abmc_counte
---
 Documentation/arch/x86/resctrl.rst     |  4 ++++
 arch/x86/kernel/cpu/resctrl/monitor.c  |  1 +
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 16 ++++++++++++++++
 3 files changed, 21 insertions(+)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index e4a7d6e815f6..1b5c05a35793 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -291,6 +291,10 @@ with the following files:
 	that case reading the mbm_total_bytes and mbm_local_bytes may report
 	'Unavailable' if there is no counter associated with that group.
 
+"num_mbm_cntrs":
+	The number of monitoring counters available for assignment when the
+	architecture supports mbm_cntr_assign mode.
+
 "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 2f3bf4529498..7aa579a99501 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -1236,6 +1236,7 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
 			r->mon.mbm_cntr_assignable = true;
 			cpuid_count(0x80000020, 5, &eax, &ebx, &ecx, &edx);
 			r->mon.num_mbm_cntrs = (ebx & GENMASK(15, 0)) + 1;
+			resctrl_file_fflags_init("num_mbm_cntrs", RFTYPE_MON_INFO);
 		}
 	}
 
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 895264c207c7..c48b5450e6c2 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -869,6 +869,16 @@ static int rdtgroup_mbm_assign_mode_show(struct kernfs_open_file *of,
 	return 0;
 }
 
+static int rdtgroup_num_mbm_cntrs_show(struct kernfs_open_file *of,
+				       struct seq_file *s, void *v)
+{
+	struct rdt_resource *r = of->kn->parent->priv;
+
+	seq_printf(s, "%d\n", r->mon.num_mbm_cntrs);
+
+	return 0;
+}
+
 #ifdef CONFIG_PROC_CPU_RESCTRL
 
 /*
@@ -1940,6 +1950,12 @@ static struct rftype res_common_files[] = {
 		.seq_show	= rdtgroup_cpus_show,
 		.fflags		= RFTYPE_BASE,
 	},
+	{
+		.name		= "num_mbm_cntrs",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= rdtgroup_num_mbm_cntrs_show,
+	},
 	{
 		.name		= "cpus_list",
 		.mode		= 0644,
-- 
2.34.1