diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index d5b0dcd1fe..11af191513 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -71,6 +71,7 @@
 #include "kvm/kvm-cpu.h"
 
 #define MAX_IDE_BUS 2
+#define XEN_IOAPIC_NUM_PIRQS 128ULL
 
 #ifdef CONFIG_IDE_ISA
 static const int ide_iobase[MAX_IDE_BUS] = { 0x1f0, 0x170 };
@@ -238,6 +239,18 @@ static void pc_init1(MachineState *machine,
         pcms->bus = pci_bus;
 
         pci_dev = pci_create_simple_multifunction(pci_bus, -1, true, type);
+
+        if (xen_enabled()) {
+            /*
+             * 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_intx_set_irq, pci_dev,
+                         XEN_IOAPIC_NUM_PIRQS);
+        }
+
         piix3 = PIIX3_PCI_DEVICE(pci_dev);
         piix3->pic = x86ms->gsi;
         piix3_devfn = piix3->dev.devfn;
diff --git a/hw/isa/piix3.c b/hw/isa/piix3.c
index 800b80f2bb..0b7e9ade0d 100644
--- a/hw/isa/piix3.c
+++ b/hw/isa/piix3.c
@@ -35,8 +35,6 @@
 #include "migration/vmstate.h"
 #include "hw/acpi/acpi_aml_interface.h"
 
-#define XEN_IOAPIC_NUM_PIRQS    128ULL
-
 static void piix3_set_irq_pic(PIIX3State *piix3, int pic_irq)
 {
     qemu_set_irq(piix3->pic[pic_irq],
@@ -403,32 +401,12 @@ 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);
-
-    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_intx_set_irq, piix3, XEN_IOAPIC_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;
+    k->realize = piix3_realize;
 }
 
 static const TypeInfo piix3_xen_info = {