s390/smp: perform initial CPU reset also for SMT siblings

commit b5e438e upstream.

Not resetting the SMT siblings might leave them in unpredictable
state. One of the observed problems was that the CPU timer wasn't
reset and therefore large system time values where accounted during
CPU bringup.

Cc: <stable@kernel.org> # 4.0
Fixes: 10ad34b ("s390: add SMT support")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/s390/kernel/smp.c

@@ -896,24 +896,12 @@ static void __no_sanitize_address smp_start_secondary(void *cpuvoid)
 /* Upping and downing of CPUs */
 int __cpu_up(unsigned int cpu, struct task_struct *tidle)
 {
-	struct pcpu *pcpu;
-	int base, i, rc;
+	struct pcpu *pcpu = pcpu_devices + cpu;
+	int rc;
 
-	pcpu = pcpu_devices + cpu;
 	if (pcpu->state != CPU_STATE_CONFIGURED)
 		return -EIO;
-	base = smp_get_base_cpu(cpu);
-	for (i = 0; i <= smp_cpu_mtid; i++) {
-		if (base + i < nr_cpu_ids)
-			if (cpu_online(base + i))
-				break;
-	}
-	/*
-	 * If this is the first CPU of the core to get online
-	 * do an initial CPU reset.
-	 */
-	if (i > smp_cpu_mtid &&
-	    pcpu_sigp_retry(pcpu_devices + base, SIGP_INITIAL_CPU_RESET, 0) !=
+	if (pcpu_sigp_retry(pcpu, SIGP_INITIAL_CPU_RESET, 0) !=
 	    SIGP_CC_ORDER_CODE_ACCEPTED)
 		return -EIO;