[HVM] Avoid long delay between setting IRQ for PV drivers and

servicing it. Should call service_ioapic() synchronously.
Signed-off-by: Keir Fraser <keir@xensource.com>

xen/arch/x86/hvm/vioapic.c

@@ -497,6 +497,8 @@ void vioapic_set_xen_irq(struct domain *d, int irq, int level)
         vioapic->irr_xen |= 1 << irq;
     else
         vioapic->irr_xen &= ~(1 << irq);
+
+    service_ioapic(vioapic);
 }
 
 void vioapic_set_irq(struct domain *d, int irq, int level)