x86/resctrl: Find and enable usable telemetry events

Every event group has a private copy of the data of all telemetry event
aggregators (aka "telemetry regions") tracking its feature type. Included
may be regions that have the same feature type but tracking different GUID
from the event group's.

Traverse the event group's telemetry region data and mark all regions that
are not usable by the event group as unusable by clearing those regions'
MMIO addresses. A region is considered unusable if:
1) GUID does not match the GUID of the event group.
2) Package ID is invalid.
3) The enumerated size of the MMIO region does not match the expected
   value from the XML description file.

Hereafter any telemetry region with an MMIO address is considered valid for
the event group it is associated with.

Enable all the event group's events as long as there is at least one usable
region from where data for its events can be read. Enabling of an event can
fail if the same event has already been enabled as part of another event
group. It should never happen that the same event is described by different
GUID supported by the same system so just WARN (via resctrl_enable_mon_event())
and skip the event.

Note that it is architecturally possible that some telemetry events are only
supported by a subset of the packages in the system. It is not expected that
systems will ever do this. If they do the user will see event files in resctrl
that always return "Unavailable".

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

1 files changed, 6 insertions, 4 deletions

diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index af43a33ce4cb..9af08b673e39 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -997,25 +997,27 @@ struct mon_evt mon_event_all[QOS_NUM_EVENTS] = {
 	MON_EVENT(PMT_EVENT_UOPS_RETIRED,		"uops_retired",		RDT_RESOURCE_PERF_PKG,	false),
 };
 
-void resctrl_enable_mon_event(enum resctrl_event_id eventid, bool any_cpu,
+bool resctrl_enable_mon_event(enum resctrl_event_id eventid, bool any_cpu,
 			      unsigned int binary_bits, void *arch_priv)
 {
 	if (WARN_ON_ONCE(eventid < QOS_FIRST_EVENT || eventid >= QOS_NUM_EVENTS ||
 			 binary_bits > MAX_BINARY_BITS))
-		return;
+		return false;
 	if (mon_event_all[eventid].enabled) {
 		pr_warn("Duplicate enable for event %d\n", eventid);
-		return;
+		return false;
 	}
 	if (binary_bits && !mon_event_all[eventid].is_floating_point) {
 		pr_warn("Event %d may not be floating point\n", eventid);
-		return;
+		return false;
 	}
 
 	mon_event_all[eventid].any_cpu = any_cpu;
 	mon_event_all[eventid].binary_bits = binary_bits;
 	mon_event_all[eventid].arch_priv = arch_priv;
 	mon_event_all[eventid].enabled = true;
+
+	return true;
 }
 
 bool resctrl_is_mon_event_enabled(enum resctrl_event_id eventid)