[RFC PATCH v3 05/17] x86/resctrl: Introduce the interface to display the assignment state

[Babu Moger]

The ABMC feature provides an option to the user to assign an RMID
to the hardware counter and monitor the bandwidth for a longer duration.
System can be in only one mode at a time (Legacy Monitor mode or ABMC
mode). By default, ABMC mode is disabled.

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

When the feature is enabled
    $cat /sys/fs/resctrl/info/L3_MON/mbm_assign
    [abmc]

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
v3: New patch to display ABMC capability.
---
 Documentation/arch/x86/resctrl.rst     |  5 +++++
 arch/x86/kernel/cpu/resctrl/monitor.c  |  4 +++-
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 17 +++++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 68df7751d1f5..cd973a013525 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -257,6 +257,11 @@ with the following files:
 	    # cat /sys/fs/resctrl/info/L3_MON/mbm_local_bytes_config
 	    0=0x30;1=0x30;3=0x15;4=0x15
 
+"mbm_assign":
+	Available when assignable monitoring features are supported.
+	Reports the list of assignable features supported and the enclosed brackets
+	indicate the feature is enabled.
+
 "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 735b449039c1..48d1957ea5a3 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -1058,8 +1058,10 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
 						 RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
 		}
 
-		if (resctrl_arch_has_abmc(r))
+		if (resctrl_arch_has_abmc(r)) {
 			r->mbm_assign_capable = ABMC_ASSIGN;
+			resctrl_file_fflags_init("mbm_assign", RFTYPE_MON_INFO);
+		}
 	}
 
 	l3_mon_evt_init(r);
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index dda71fb6c10e..5ec807e8dd38 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -846,6 +846,17 @@ static int rdtgroup_rmid_show(struct kernfs_open_file *of,
 	return ret;
 }
 
+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;
+
+	if (r->mbm_assign_capable)
+		seq_puts(s, "abmc\n");
+
+	return 0;
+}
+
 #ifdef CONFIG_PROC_CPU_RESCTRL
 
 /*
@@ -1903,6 +1914,12 @@ 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