KVM: x86: reset edge sense circuit of i8259 on init

The spec says that during initialization "The edge sense circuit is
reset which means that following initialization an interrupt request
(IR) input must make a low-to-high transition to generate an interrupt",
but currently if edge triggered interrupt is in IRR it is delivered
after i8259 initialization.

Signed-off-by: Gleb Natapov <[email protected]>
Signed-off-by: Marcelo Tosatti <[email protected]>
Signed-off-by: Avi Kivity <[email protected]>

arch/x86/kvm/i8259.c

@@ -307,6 +307,7 @@ static void pic_ioport_write(void *opaque, u32 addr, u32 val)
 		if (val & 0x10) {
 			s->init4 = val & 1;
 			s->last_irr = 0;
+			s->irr &= s->elcr;
 			s->imr = 0;
 			s->priority_add = 0;
 			s->special_mask = 0;