fs/resctrl: Split L3 dependent parts out of __mon_event_count()

Carve out the L3 resource specific event reading code into a separate helper
to support reading event data from a new monitoring resource.

Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/20251217172121.12030-1-tony.luck@intel.com

Author: aegl

fs/resctrl/monitor.c

@@ -413,7 +413,7 @@ static void mbm_cntr_free(struct rdt_mon_domain *d, int cntr_id)
 	memset(&d->cntr_cfg[cntr_id], 0, sizeof(*d->cntr_cfg));
 }
 
-static int __mon_event_count(struct rdtgroup *rdtgrp, struct rmid_read *rr)
+static int __l3_mon_event_count(struct rdtgroup *rdtgrp, struct rmid_read *rr)
 {
 	int cpu = smp_processor_id();
 	u32 closid = rdtgrp->closid;
@@ -494,6 +494,17 @@ static int __mon_event_count(struct rdtgroup *rdtgrp, struct rmid_read *rr)
 	return ret;
 }
 
+static int __mon_event_count(struct rdtgroup *rdtgrp, struct rmid_read *rr)
+{
+	switch (rr->r->rid) {
+	case RDT_RESOURCE_L3:
+		return __l3_mon_event_count(rdtgrp, rr);
+	default:
+		rr->err = -EINVAL;
+		return -EINVAL;
+	}
+}
+
 /*
  * mbm_bw_count() - Update bw count from values previously read by
  *		    __mon_event_count().