x86/resctrl: Add "mba_MBps_event" file to CTRL_MON directories

The "mba_MBps" mount option provides an alternate method to control memory
bandwidth. Instead of specifying allowable bandwidth as a percentage of
maximum possible, the user provides a MiB/s limit value.

In preparation to allow the user to pick the memory bandwidth monitoring event
used as input to the feedback loop, provide a file in each CTRL_MON group
directory that shows the event currently in use. Note that this file is only
visible when the "mba_MBps" mount option is in use.

Suggested-by: Reinette Chatre <[email protected]>
Signed-off-by: Tony Luck <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Reviewed-by: Reinette Chatre <[email protected]>
Tested-by: Babu Moger <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: aegl

arch/x86/kernel/cpu/resctrl/ctrlmondata.c

@@ -518,6 +518,36 @@ static int smp_mon_event_count(void *arg)
 	return 0;
 }
 
+int rdtgroup_mba_mbps_event_show(struct kernfs_open_file *of,
+				 struct seq_file *s, void *v)
+{
+	struct rdtgroup *rdtgrp;
+	int ret = 0;
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+
+	if (rdtgrp) {
+		switch (rdtgrp->mba_mbps_event) {
+		case QOS_L3_MBM_LOCAL_EVENT_ID:
+			seq_puts(s, "mbm_local_bytes\n");
+			break;
+		case QOS_L3_MBM_TOTAL_EVENT_ID:
+			seq_puts(s, "mbm_total_bytes\n");
+			break;
+		default:
+			pr_warn_once("Bad event %d\n", rdtgrp->mba_mbps_event);
+			ret = -EINVAL;
+			break;
+		}
+	} else {
+		ret = -ENOENT;
+	}
+
+	rdtgroup_kn_unlock(of->kn);
+
+	return ret;
+}
+
 void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
 		    struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
 		    cpumask_t *cpumask, int evtid, int first)

arch/x86/kernel/cpu/resctrl/internal.h

@@ -610,6 +610,8 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
 				char *buf, size_t nbytes, loff_t off);
 int rdtgroup_schemata_show(struct kernfs_open_file *of,
 			   struct seq_file *s, void *v);
+int rdtgroup_mba_mbps_event_show(struct kernfs_open_file *of,
+				 struct seq_file *s, void *v);
 bool rdtgroup_cbm_overlaps(struct resctrl_schema *s, struct rdt_ctrl_domain *d,
 			   unsigned long cbm, int closid, bool exclusive);
 unsigned int rdtgroup_cbm_to_size(struct rdt_resource *r, struct rdt_ctrl_domain *d,

arch/x86/kernel/cpu/resctrl/rdtgroup.c

@@ -1950,6 +1950,12 @@ static struct rftype res_common_files[] = {
 		.seq_show	= rdtgroup_schemata_show,
 		.fflags		= RFTYPE_CTRL_BASE,
 	},
+	{
+		.name		= "mba_MBps_event",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= rdtgroup_mba_mbps_event_show,
+	},
 	{
 		.name		= "mode",
 		.mode		= 0644,
@@ -2355,6 +2361,7 @@ static int set_mba_sc(bool mba_sc)
 	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
 	u32 num_closid = resctrl_arch_get_num_closid(r);
 	struct rdt_ctrl_domain *d;
+	unsigned long fflags;
 	int i;
 
 	if (!supports_mba_mbps() || mba_sc == is_mba_sc(r))
@@ -2369,6 +2376,9 @@ static int set_mba_sc(bool mba_sc)
 			d->mbps_val[i] = MBA_MAX_MBPS;
 	}
 
+	fflags = mba_sc ? RFTYPE_CTRL_BASE | RFTYPE_MON_BASE : 0;
+	resctrl_file_fflags_init("mba_MBps_event", fflags);
+
 	return 0;
 }