i8259: Do not clear level-triggered lines in IRR on init

When an input line is handled as level-triggered, it will immediately
raise an IRQ on the output of a PIC again that goes through an init
reset. So only clear the edge-triggered inputs from IRR in that
scenario.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/i8259.c

@@ -231,8 +231,8 @@ static void pic_reset(DeviceState *dev)
 {
     PICCommonState *s = DO_UPCAST(PICCommonState, dev.qdev, dev);
 
-    pic_init_reset(s);
     s->elcr = 0;
+    pic_init_reset(s);
 }
 
 static void pic_ioport_write(void *opaque, target_phys_addr_t addr64,

hw/i8259_common.c

@@ -28,7 +28,7 @@
 void pic_reset_common(PICCommonState *s)
 {
     s->last_irr = 0;
-    s->irr = 0;
+    s->irr &= s->elcr;
     s->imr = 0;
     s->isr = 0;
     s->priority_add = 0;

hw/kvm/i8259.c

@@ -84,8 +84,8 @@ static void kvm_pic_reset(DeviceState *dev)
 {
     PICCommonState *s = DO_UPCAST(PICCommonState, dev.qdev, dev);
 
-    pic_reset_common(s);
     s->elcr = 0;
+    pic_reset_common(s);
 
     kvm_pic_put(s);
 }