s390/irq,idle: simplify idle check

Use the per-cpu CIF_ENABLED_WAIT flag to decide if an interrupt
occurred while a cpu was idle, instead of checking two conditions
within the old psw.

Also move clearing of the CIF_ENABLED_WAIT bit to the early interrupt
handler, which in turn makes arch_vcpu_is_preempted() also a bit more
precise, since the flag is now cleared before interrupt handlers have
been called.
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/include/asm/idle.h

@@ -23,6 +23,5 @@ extern struct device_attribute dev_attr_idle_count;
 extern struct device_attribute dev_attr_idle_time_us;
 
 void psw_idle(struct s390_idle_data *data, unsigned long psw_mask);
-void psw_idle_exit(void);
 
 #endif /* _S390_IDLE_H */

arch/s390/kernel/idle.c

@@ -28,7 +28,6 @@ void account_idle_time_irq(void)
 	u64 cycles_new[8];
 	int i;
 
-	clear_cpu_flag(CIF_ENABLED_WAIT);
 	if (smp_cpu_mtid) {
 		stcctm(MT_DIAG, smp_cpu_mtid, cycles_new);
 		for (i = 0; i < smp_cpu_mtid; i++)

arch/s390/kernel/irq.c

@@ -136,7 +136,7 @@ void noinstr do_io_irq(struct pt_regs *regs)
 {
 	irqentry_state_t state = irqentry_enter(regs);
 	struct pt_regs *old_regs = set_irq_regs(regs);
-	int from_idle;
+	bool from_idle;
 
 	irq_enter_rcu();
 
@@ -146,7 +146,7 @@ void noinstr do_io_irq(struct pt_regs *regs)
 			current->thread.last_break = regs->last_break;
 	}
 
-	from_idle = !user_mode(regs) && regs->psw.addr == (unsigned long)psw_idle_exit;
+	from_idle = test_and_clear_cpu_flag(CIF_ENABLED_WAIT);
 	if (from_idle)
 		account_idle_time_irq();
 
@@ -171,7 +171,7 @@ void noinstr do_ext_irq(struct pt_regs *regs)
 {
 	irqentry_state_t state = irqentry_enter(regs);
 	struct pt_regs *old_regs = set_irq_regs(regs);
-	int from_idle;
+	bool from_idle;
 
 	irq_enter_rcu();
 
@@ -185,7 +185,7 @@ void noinstr do_ext_irq(struct pt_regs *regs)
 	regs->int_parm = S390_lowcore.ext_params;
 	regs->int_parm_long = S390_lowcore.ext_params2;
 
-	from_idle = !user_mode(regs) && regs->psw.addr == (unsigned long)psw_idle_exit;
+	from_idle = test_and_clear_cpu_flag(CIF_ENABLED_WAIT);
 	if (from_idle)
 		account_idle_time_irq();