KVM: s390: optimize interrupt handling round trip time
We can avoid checking guest control registers and guest PSW as well
as all the masking and calculations on the interrupt masks when
no interrupts are pending.
Also, the check for IRQ_PEND_COUNT can be removed, because we won't
enter the while loop if no interrupts are pending and invalid interrupt
types can't be injected.
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 2836b25..acf4a4e 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -134,6 +134,8 @@
active_mask = pending_local_irqs(vcpu);
active_mask |= pending_floating_irqs(vcpu);
+ if (!active_mask)
+ return 0;
if (psw_extint_disabled(vcpu))
active_mask &= ~IRQ_PEND_EXT_MASK;
@@ -941,12 +943,9 @@
if (cpu_timer_irq_pending(vcpu))
set_bit(IRQ_PEND_EXT_CPU_TIMER, &li->pending_irqs);
- do {
- irqs = deliverable_irqs(vcpu);
+ while ((irqs = deliverable_irqs(vcpu)) && !rc) {
/* bits are in the order of interrupt priority */
irq_type = find_first_bit(&irqs, IRQ_PEND_COUNT);
- if (irq_type == IRQ_PEND_COUNT)
- break;
if (is_ioirq(irq_type)) {
rc = __deliver_io(vcpu, irq_type);
} else {
@@ -958,9 +957,7 @@
}
rc = func(vcpu);
}
- if (rc)
- break;
- } while (!rc);
+ }
set_intercept_indicators(vcpu);