[PATCH v5 5/7] hw/isa/vt82c686: Work around missing level sensitive irq in i8259 model

[BALATON Zoltan]

MorphOS sets the ISA PIC to level sensitive mode but QEMU does not
support that so this causes a freeze if multiple devices try to raise
a shared interrupt. Work around it by lowering the interrupt before
raising it again if it is already raised. This could be reverted when
the i8259 model is fixed.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
 hw/isa/vt82c686.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/hw/isa/vt82c686.c b/hw/isa/vt82c686.c
index 018a119964..3e44a51f92 100644
--- a/hw/isa/vt82c686.c
+++ b/hw/isa/vt82c686.c
@@ -549,6 +549,7 @@ struct ViaISAState {
     PCIDevice dev;
     qemu_irq cpu_intr;
     qemu_irq *isa_irqs_in;
+    uint16_t isa_irqs_state;
     ViaSuperIOState via_sio;
     MC146818RtcState rtc;
     PCIIDEState ide;
@@ -636,6 +637,14 @@ static void via_isa_set_pci_irq(void *opaque, int irq_num, 
int level)
             pic_level |= pci_bus_get_irq_level(bus, i);
         }
     }
+    /* FIXME: workaround for i8259: level sensitive irq not supported */
+    if ((s->isa_irqs_state & BIT(pic_irq)) && pic_level) {
+        qemu_irq_lower(s->isa_irqs_in[pic_irq]);
+    } else if (pic_level) {
+        s->isa_irqs_state |= BIT(pic_irq);
+    } else {
+        s->isa_irqs_state &= ~BIT(pic_irq);
+    }
     /* Now we change the pic irq level according to the via irq mappings. */
     qemu_set_irq(s->isa_irqs_in[pic_irq], pic_level);
 }
-- 
2.30.8