diff --git a/hw/isa/piix.c b/hw/isa/piix.c
index 449c1baaab..17677c2126 100644
--- a/hw/isa/piix.c
+++ b/hw/isa/piix.c
@@ -81,27 +81,6 @@ static void piix_set_pci_irq(void *opaque, int pirq, int level)
     piix_set_pci_irq_level(s, pirq, level);
 }
 
-static void piix4_set_irq(void *opaque, int irq_num, int level)
-{
-    int i, pic_irq, pic_level;
-    PIIXState *s = opaque;
-    PCIBus *bus = pci_get_bus(&s->dev);
-
-    /* now we change the pic irq level according to the piix irq mappings */
-    /* XXX: optimize */
-    pic_irq = s->dev.config[PIIX_PIRQCA + irq_num];
-    if (pic_irq < ISA_NUM_IRQS) {
-        /* The pic level is the logical OR of all the PCI irqs mapped to it. */
-        pic_level = 0;
-        for (i = 0; i < PIIX_NUM_PIRQS; i++) {
-            if (pic_irq == s->dev.config[PIIX_PIRQCA + i]) {
-                pic_level |= pci_bus_get_irq_level(bus, i);
-            }
-        }
-        qemu_set_irq(s->isa_irqs_in[pic_irq], pic_level);
-    }
-}
-
 static void piix_request_i8259_irq(void *opaque, int irq, int level)
 {
     PIIXState *s = opaque;
@@ -223,7 +202,7 @@ static int piix4_post_load(void *opaque, int version_id)
         s->rcr = 0;
     }
 
-    return 0;
+    return piix_post_load(opaque, version_id);
 }
 
 static int piix3_pre_save(void *opaque)
@@ -442,6 +421,7 @@ static void pci_piix_class_init(ObjectClass *klass, void *data)
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
     AcpiDevAmlIfClass *adevc = ACPI_DEV_AML_IF_CLASS(klass);
 
+    k->config_write = piix_write_config;
     dc->reset       = piix_reset;
     dc->desc        = "ISA bridge";
     dc->hotpluggable   = false;
@@ -497,7 +477,6 @@ static void piix3_class_init(ObjectClass *klass, void *data)
     DeviceClass *dc = DEVICE_CLASS(klass);
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
 
-    k->config_write = piix_write_config;
     k->realize = piix3_realize;
     /* 82371SB PIIX3 PCI-to-ISA bridge (Step A1) */
     k->device_id = PCI_DEVICE_ID_INTEL_82371SB_0;
@@ -522,7 +501,7 @@ static void piix4_realize(PCIDevice *dev, Error **errp)
         return;
     }
 
-    pci_bus_irqs(pci_bus, piix4_set_irq, s, PIIX_NUM_PIRQS);
+    pci_bus_irqs(pci_bus, piix_set_pci_irq, s, PIIX_NUM_PIRQS);
 }
 
 static void piix4_init(Object *obj)