powerpc/pseries: Honour current SMT state when DLPAR onlining CPUs

Integrate with the generic SMT support, so that when a CPU is DLPAR
onlined it is brought up with the correct SMT mode.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230705145143.40545-11-ldufour@linux.ibm.com

arch/powerpc/platforms/pseries/hotplug-cpu.c

@@ -398,6 +398,14 @@ static int dlpar_online_cpu(struct device_node *dn)
 		for_each_present_cpu(cpu) {
 			if (get_hard_smp_processor_id(cpu) != thread)
 				continue;
+
+			if (!topology_is_primary_thread(cpu)) {
+				if (cpu_smt_control != CPU_SMT_ENABLED)
+					break;
+				if (!topology_smt_thread_allowed(cpu))
+					break;
+			}
+
 			cpu_maps_update_done();
 			find_and_update_cpu_nid(cpu);
 			rc = device_online(get_cpu_device(cpu));