KVM: fix i8259 reset irq acking

[Marcelo Tosatti <mtosatti@redhat.com>]

The irq ack during pic reset has three problems:

- Ignores slave/master PIC, using gsi 0-8 for both.
- Generates an ACK even if the APIC is in control.
- Depends upon IMR being clear, which is broken if the 
irq was masked at the time it was generated.

The last one causes the BIOS to hang after the first reboot of Windows
installation, since PIT interrupts stop.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>


diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index de70499..2b42d48 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -195,14 +195,18 @@ int kvm_pic_read_irq(struct kvm *kvm)
 
 void kvm_pic_reset(struct kvm_kpic_state *s)
 {
-	int irq;
+	int irq, irqbase;
 	struct kvm *kvm = s->pics_state->irq_request_opaque;
 
-	for (irq = 0; irq < PIC_NUM_PINS; irq++) {
-		if (!(s->imr & (1 << irq)) && (s->irr & (1 << irq) ||
-		    s->isr & (1 << irq)))
-			kvm_notify_acked_irq(kvm, irq);
-	}
+	if (s == &s->pics_state->pics[0])
+		irqbase = 0;
+	else
+		irqbase = 8;
+
+	if (!kvm_lapic_enabled(kvm->vcpus[0]))
+		for (irq = 0; irq < PIC_NUM_PINS/2; irq++)
+			if (s->irr & (1 << irq) || s->isr & (1 << irq))
+				kvm_notify_acked_irq(kvm, irq+irqbase);
 	s->last_irr = 0;
 	s->irr = 0;
 	s->imr = 0;