s390/smp,mcck: fix early IPI handling

Both the external call as well as the emergency signal submask bits in
control register 0 are set before any interrupt handler is registered.

Change the order and first register the interrupt handler and only then
enable the interrupts by setting the corresponding bits in control
register 0.

This prevents that the second part of the machine check handler for
early machine check handling is not executed: the machine check handler
sends an IPI to the CPU it runs on. If the corresponding interrupts are
enabled, but no interrupt handler is present, the interrupt is ignored.
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/kernel/early.c

@@ -258,15 +258,9 @@ static inline void save_vector_registers(void)
 #endif
 }
 
-static inline void setup_control_registers(void)
+static inline void setup_low_address_protection(void)
 {
-	unsigned long reg;
-
-	__ctl_store(reg, 0, 0);
-	reg |= CR0_LOW_ADDRESS_PROTECTION;
-	reg |= CR0_EMERGENCY_SIGNAL_SUBMASK;
-	reg |= CR0_EXTERNAL_CALL_SUBMASK;
-	__ctl_load(reg, 0, 0);
+	__ctl_set_bit(0, 28);
 }
 
 static inline void setup_access_registers(void)
@@ -314,7 +308,7 @@ void __init startup_init(void)
 	save_vector_registers();
 	setup_topology();
 	sclp_early_detect();
-	setup_control_registers();
+	setup_low_address_protection();
 	setup_access_registers();
 	lockdep_on();
 }

arch/s390/kernel/smp.c

@@ -1013,12 +1013,12 @@ void __init smp_fill_possible_mask(void)
 
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
-	/* request the 0x1201 emergency signal external interrupt */
 	if (register_external_irq(EXT_IRQ_EMERGENCY_SIG, do_ext_call_interrupt))
 		panic("Couldn't request external interrupt 0x1201");
-	/* request the 0x1202 external call external interrupt */
+	ctl_set_bit(0, 14);
 	if (register_external_irq(EXT_IRQ_EXTERNAL_CALL, do_ext_call_interrupt))
 		panic("Couldn't request external interrupt 0x1202");
+	ctl_set_bit(0, 13);
 }
 
 void __init smp_prepare_boot_cpu(void)