x86/resctrl: Enable RDT_RESOURCE_PERF_PKG

Since telemetry events are enumerated on resctrl mount the RDT_RESOURCE_PERF_PKG
resource is not considered "monitoring capable" during early resctrl initialization.
This means that the domain list for RDT_RESOURCE_PERF_PKG is not built when the CPU
hotplug notifiers are registered and run for the first time right after resctrl
initialization.

Mark the RDT_RESOURCE_PERF_PKG as "monitoring capable" upon successful telemetry
event enumeration to ensure future CPU hotplug events include this resource and
initialize its domain list for CPUs that are already online.

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

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

@@ -766,8 +766,24 @@ static int resctrl_arch_offline_cpu(unsigned int cpu)
 
 void resctrl_arch_pre_mount(void)
 {
+	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_PERF_PKG].r_resctrl;
+	int cpu;
+
 	if (!intel_aet_get_events())
 		return;
+
+	/*
+	 * Late discovery of telemetry events means the domains for the
+	 * resource were not built. Do that now.
+	 */
+	cpus_read_lock();
+	mutex_lock(&domain_list_lock);
+	r->mon_capable = true;
+	rdt_mon_capable = true;
+	for_each_online_cpu(cpu)
+		domain_add_cpu_mon(cpu, r);
+	mutex_unlock(&domain_list_lock);
+	cpus_read_unlock();
 }
 
 enum {

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

@@ -270,6 +270,12 @@ static bool enable_events(struct event_group *e, struct pmt_feature_group *p)
 	else
 		r->mon.num_rmid = e->num_rmid;
 
+	if (skipped_events)
+		pr_info("%s %s:0x%x monitoring detected (skipped %d events)\n", r->name,
+			e->pfname, e->guid, skipped_events);
+	else
+		pr_info("%s %s:0x%x monitoring detected\n", r->name, e->pfname, e->guid);
+
 	return true;
 }