diff --git a/hw/isa/piix3.c b/hw/isa/piix3.c
index 7d69420967..d15117a7c7 100644
--- a/hw/isa/piix3.c
+++ b/hw/isa/piix3.c
@@ -24,6 +24,7 @@
 
 #include "qemu/osdep.h"
 #include "qemu/range.h"
+#include "qapi/error.h"
 #include "hw/southbridge/piix.h"
 #include "hw/irq.h"
 #include "hw/isa/isa.h"
@@ -280,7 +281,7 @@ static const MemoryRegionOps rcr_ops = {
     .endianness = DEVICE_LITTLE_ENDIAN
 };
 
-static void piix3_realize(PCIDevice *dev, Error **errp)
+static void pci_piix3_realize(PCIDevice *dev, Error **errp)
 {
     PIIX3State *d = PIIX3_PCI_DEVICE(dev);
 
@@ -305,7 +306,6 @@ static void pci_piix3_class_init(ObjectClass *klass, void *data)
     dc->desc        = "ISA bridge";
     dc->vmsd        = &vmstate_piix3;
     dc->hotpluggable   = false;
-    k->realize      = piix3_realize;
     k->vendor_id    = PCI_VENDOR_ID_INTEL;
     /* 82371SB PIIX3 PCI-to-ISA bridge (Step A1) */
     k->device_id    = PCI_DEVICE_ID_INTEL_82371SB_0;
@@ -329,11 +329,28 @@ static const TypeInfo piix3_pci_type_info = {
     },
 };
 
+static void piix3_realize(PCIDevice *dev, Error **errp)
+{
+    ERRP_GUARD();
+    PIIX3State *piix3 = PIIX3_PCI_DEVICE(dev);
+    PCIBus *pci_bus = pci_get_bus(dev);
+
+    pci_piix3_realize(dev, errp);
+    if (*errp) {
+        return;
+    }
+
+    pci_bus_irqs(pci_bus, piix3_set_irq, pci_slot_get_pirq,
+                 piix3, PIIX_NUM_PIRQS);
+    pci_bus_set_route_irq_fn(pci_bus, piix3_route_intx_pin_to_irq);
+};
+
 static void piix3_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
 
     k->config_write = piix3_write_config;
+    k->realize = piix3_realize;
 }
 
 static const TypeInfo piix3_info = {
@@ -342,11 +359,33 @@ static const TypeInfo piix3_info = {
     .class_init    = piix3_class_init,
 };
 
+static void piix3_xen_realize(PCIDevice *dev, Error **errp)
+{
+    ERRP_GUARD();
+    PIIX3State *piix3 = PIIX3_PCI_DEVICE(dev);
+    PCIBus *pci_bus = pci_get_bus(dev);
+
+    pci_piix3_realize(dev, errp);
+    if (*errp) {
+        return;
+    }
+
+    /*
+     * Xen supports additional interrupt routes from the PCI devices to
+     * the IOAPIC: the four pins of each PCI device on the bus are also
+     * connected to the IOAPIC directly.
+     * These additional routes can be discovered through ACPI.
+     */
+    pci_bus_irqs(pci_bus, xen_piix3_set_irq, xen_pci_slot_get_pirq,
+                 piix3, XEN_PIIX_NUM_PIRQS);
+};
+
 static void piix3_xen_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
 
     k->config_write = piix3_write_config_xen;
+    k->realize = piix3_xen_realize;
 };
 
 static const TypeInfo piix3_xen_info = {
@@ -368,27 +407,11 @@ PIIX3State *piix3_create(PCIBus *pci_bus, ISABus **isa_bus)
 {
     PIIX3State *piix3;
     PCIDevice *pci_dev;
+    const char *type = xen_enabled() ? TYPE_PIIX3_XEN_DEVICE
+                                     : TYPE_PIIX3_DEVICE;
 
-    /*
-     * Xen supports additional interrupt routes from the PCI devices to
-     * the IOAPIC: the four pins of each PCI device on the bus are also
-     * connected to the IOAPIC directly.
-     * These additional routes can be discovered through ACPI.
-     */
-    if (xen_enabled()) {
-        pci_dev = pci_create_simple_multifunction(pci_bus, -1, true,
-                                                  TYPE_PIIX3_XEN_DEVICE);
-        piix3 = PIIX3_PCI_DEVICE(pci_dev);
-        pci_bus_irqs(pci_bus, xen_piix3_set_irq, xen_pci_slot_get_pirq,
-                     piix3, XEN_PIIX_NUM_PIRQS);
-    } else {
-        pci_dev = pci_create_simple_multifunction(pci_bus, -1, true,
-                                                  TYPE_PIIX3_DEVICE);
-        piix3 = PIIX3_PCI_DEVICE(pci_dev);
-        pci_bus_irqs(pci_bus, piix3_set_irq, pci_slot_get_pirq,
-                     piix3, PIIX_NUM_PIRQS);
-        pci_bus_set_route_irq_fn(pci_bus, piix3_route_intx_pin_to_irq);
-    }
+    pci_dev = pci_create_simple_multifunction(pci_bus, -1, true, type);
+    piix3 = PIIX3_PCI_DEVICE(pci_dev);
     *isa_bus = ISA_BUS(qdev_get_child_bus(DEVICE(piix3), "isa.0"));
 
     return piix3;
diff --git a/hw/isa/piix4.c b/hw/isa/piix4.c
index a223b69e24..134d23aea7 100644
--- a/hw/isa/piix4.c
+++ b/hw/isa/piix4.c
@@ -204,6 +204,8 @@ static const MemoryRegionOps piix4_rcr_ops = {
 static void piix4_realize(PCIDevice *dev, Error **errp)
 {
     PIIX4State *s = PIIX4_PCI_DEVICE(dev);
+    PCIDevice *pci;
+    PCIBus *pci_bus = pci_get_bus(dev);
     ISABus *isa_bus;
     qemu_irq *i8259_out_irq;
 
@@ -242,6 +244,15 @@ static void piix4_realize(PCIDevice *dev, Error **errp)
         return;
     }
     s->rtc.irq = isa_get_irq(ISA_DEVICE(&s->rtc), s->rtc.isairq);
+
+    /* IDE */
+    pci = pci_create_simple(pci_bus, dev->devfn + 1, "piix4-ide");
+    pci_ide_create_devs(pci);
+
+    /* USB */
+    pci_create_simple(pci_bus, dev->devfn + 2, "piix4-usb-uhci");
+
+    pci_bus_irqs(pci_bus, piix4_set_irq, pci_slot_get_pirq, s, PIIX_NUM_PIRQS);
 }
 
 static void piix4_init(Object *obj)
@@ -292,7 +303,6 @@ type_init(piix4_register_types)
 
 DeviceState *piix4_create(PCIBus *pci_bus, ISABus **isa_bus, I2CBus **smbus)
 {
-    PIIX4State *s;
     PCIDevice *pci;
     DeviceState *dev;
     int devfn = PCI_DEVFN(10, 0);
@@ -300,22 +310,16 @@ DeviceState *piix4_create(PCIBus *pci_bus, ISABus **isa_bus, I2CBus **smbus)
     pci = pci_create_simple_multifunction(pci_bus, devfn,  true,
                                           TYPE_PIIX4_PCI_DEVICE);
     dev = DEVICE(pci);
-    s = PIIX4_PCI_DEVICE(pci);
+
     if (isa_bus) {
         *isa_bus = ISA_BUS(qdev_get_child_bus(dev, "isa.0"));
     }
 
-    pci = pci_create_simple(pci_bus, devfn + 1, "piix4-ide");
-    pci_ide_create_devs(pci);
-
-    pci_create_simple(pci_bus, devfn + 2, "piix4-usb-uhci");
     if (smbus) {
         *smbus = piix4_pm_init(pci_bus, devfn + 3, 0x1100,
                                qdev_get_gpio_in_named(dev, "isa", 9),
                                NULL, 0, NULL);
     }
 
-    pci_bus_irqs(pci_bus, piix4_set_irq, pci_slot_get_pirq, s, PIIX_NUM_PIRQS);
-
     return dev;
 }
