[PATCH v7 08/24] x86/resctrl: Introduce interface to display number of monitoring counters

[Babu Moger]

The mbm_assign_cntr mode provides an option to the user to assign a
hardware 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.

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
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     |  3 +++
 arch/x86/kernel/cpu/resctrl/monitor.c  |  1 +
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 16 ++++++++++++++++
 3 files changed, 20 insertions(+)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index a7b17ad8acb9..3e9302971faf 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -290,6 +290,9 @@ with the following files:
 	than 'num_mbm_cntrs' to be created. Reading the mbm files may report 'Unavailable'
 	if there is no hardware resource assigned.
 
+"num_mbm_cntrs":
+	The number of monitoring counters available for assignment.
+
 "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 71fab31e20da..e3e71843401a 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 & 0xFFFF) + 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 dbc8c5e63213..ba737890d5c2 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