perf/arm-cmn: Validate cycles events fully

DTC cycle count events don't have anything to validate or initialise in
themselves, but we should not forget to still validate their whole group
context. Otherwise, we may fail to correctly reject a contrived group
containing an impossible number of cycles events.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/3124e8c276a1f513c1a415dc839ca4181b3c8bc8.1680522545.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

Author: rmurphy-arm

drivers/perf/arm-cmn.c

@@ -1546,7 +1546,7 @@ static int arm_cmn_event_init(struct perf_event *event)
 	type = CMN_EVENT_TYPE(event);
 	/* DTC events (i.e. cycles) already have everything they need */
 	if (type == CMN_TYPE_DTC)
-		return 0;
+		return arm_cmn_validate_group(cmn, event);
 
 	eventid = CMN_EVENT_EVENTID(event);
 	/* For watchpoints we need the actual XP node here */