powerpc/pseries: Avoid harmless preempt warning

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200320152436.1468651-1-npiggin@gmail.com

arch/powerpc/platforms/pseries/lpar.c

@@ -636,8 +636,16 @@ static const struct proc_ops vcpudispatch_stats_freq_proc_ops = {
 
 static int __init vcpudispatch_stats_procfs_init(void)
 {
-	if (!lppaca_shared_proc(get_lppaca()))
+	/*
+	 * Avoid smp_processor_id while preemptible. All CPUs should have
+	 * the same value for lppaca_shared_proc.
+	 */
+	preempt_disable();
+	if (!lppaca_shared_proc(get_lppaca())) {
+		preempt_enable();
 		return 0;
+	}
+	preempt_enable();
 
 	if (!proc_create("powerpc/vcpudispatch_stats", 0600, NULL,
 					&vcpudispatch_stats_proc_ops))