pc: Fix and clean up PIC-to-APIC IRQ path

The master PIC is connected to the LINTIN0 of the APICs. As the APIC
currently does not track the state of that line, we have to ask the PIC
to reinject its IRQ after the CPU picked up an event from the APIC.

This introduces pic_get_output to read the master PIC IRQ line state
without changing it. The APIC uses this function to decide if a PIC IRQ
should be reinjected on apic_update_irq. This reflects better how the
real hardware works.

The patch fixes some failures of the kvm unit tests apic and eventinj by
allowing to enable the proper CPU IRQ deassertion when the guest masks
some pending IRQs at PIC level.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

1 files changed, 7 insertions, 8 deletions

diff --git a/hw/i8259.c b/hw/i8259.c
index e5323ff..6006123 100644
--- a/hw/i8259.c
+++ b/hw/i8259.c
@@ -146,8 +146,7 @@ static int pic_get_irq(PicState *s)
 
 /* raise irq to CPU if necessary. must be called every time the active
    irq may change */
-/* XXX: should not export it, but it is needed for an APIC kludge */
-void pic_update_irq(PicState2 *s)
+static void pic_update_irq(PicState2 *s)
 {
     int irq2, irq;
 
@@ -174,14 +173,9 @@ void pic_update_irq(PicState2 *s)
         printf("pic: cpu_interrupt\n");
 #endif
         qemu_irq_raise(s->parent_irq);
-    }
-
-/* all targets should do this rather than acking the IRQ in the cpu */
-#if defined(TARGET_MIPS) || defined(TARGET_PPC) || defined(TARGET_ALPHA)
-    else {
+    } else {
         qemu_irq_lower(s->parent_irq);
     }
-#endif
 }
 
 #ifdef DEBUG_IRQ_LATENCY
@@ -441,6 +435,11 @@ uint32_t pic_intack_read(PicState2 *s)
     return ret;
 }
 
+int pic_get_output(PicState2 *s)
+{
+    return (pic_get_irq(&s->pics[0]) >= 0);
+}
+
 static void elcr_ioport_write(void *opaque, target_phys_addr_t addr,
                               uint64_t val, unsigned size)
 {