[PATCH v4 08/19] x86/resctrl: Introduce the interface to display monitor mode

[Babu Moger]

The ABMC feature provides an option to the user to assign a hardware
counter to an RMID and monitor the bandwidth as long as it is assigned.
ABMC mode is enabled by default when supported. System can be one mode
at a time (Legacy monitor mode or ABMC mode).

Provide an interface to display the monitor mode on the system.
    $cat /sys/fs/resctrl/info/L3_MON/mbm_assign
    [abmc]
    legacy

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
v4: Fixed the checks for legacy and abmc mode. Default it ABMC.

v3: New patch to display ABMC capability.
---
 Documentation/arch/x86/resctrl.rst     | 10 ++++++++++
 arch/x86/kernel/cpu/resctrl/monitor.c  |  1 +
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 23 +++++++++++++++++++++++
 3 files changed, 34 insertions(+)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 7ab8172ef208..ab3cde61a124 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -261,6 +261,16 @@ with the following files:
 	Available when ABMC feature is supported. The number of ABMC counters
 	available for configuration.
 
+"mbm_assign":
+	Available when ABMC feature is supported. Reports the list of assignable
+	monitoring features supported. The enclosed brackets indicate which
+	feature is enabled.
+	::
+
+	  cat /sys/fs/resctrl/info/L3_MON/mbm_assign
+	  [abmc]
+	  mbm_legacy
+
 "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 e75a6146068b..b1d002e5e93d 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -1071,6 +1071,7 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
 
 		if (rdt_cpu_has(X86_FEATURE_ABMC)) {
 			r->abmc_capable = true;
+			resctrl_file_fflags_init("mbm_assign", RFTYPE_MON_INFO);
 			/*
 			 * Query CPUID_Fn80000020_EBX_x05 for number of
 			 * ABMC counters
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 9148d1234ede..3071bbb7a15e 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -856,6 +856,23 @@ static int rdtgroup_num_cntrs_show(struct kernfs_open_file *of,
 	return 0;
 }
 
+static int rdtgroup_mbm_assign_show(struct kernfs_open_file *of,
+				    struct seq_file *s, void *v)
+{
+	struct rdt_resource *r = of->kn->parent->priv;
+	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
+
+	if (hw_res->abmc_enabled) {
+		seq_puts(s, "[abmc]\n");
+		seq_puts(s, "mbm_legacy\n");
+	} else {
+		seq_puts(s, "abmc\n");
+		seq_puts(s, "[mbm_legacy]\n");
+	}
+
+	return 0;
+}
+
 #ifdef CONFIG_PROC_CPU_RESCTRL
 
 /*
@@ -1913,6 +1930,12 @@ static struct rftype res_common_files[] = {
 		.seq_show	= mbm_local_bytes_config_show,
 		.write		= mbm_local_bytes_config_write,
 	},
+	{
+		.name		= "mbm_assign",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= rdtgroup_mbm_assign_show,
+	},
 	{
 		.name		= "cpus",
 		.mode		= 0644,
-- 
2.34.1