diff --git a/hw/pci-host/pnv_phb3.c b/hw/pci-host/pnv_phb3.c
index d58d3c1701..058cbab555 100644
--- a/hw/pci-host/pnv_phb3.c
+++ b/hw/pci-host/pnv_phb3.c
@@ -986,6 +986,28 @@ static void pnv_phb3_instance_init(Object *obj)
 
 }
 
+void pnv_phb3_bus_init(DeviceState *dev, PnvPHB3 *phb)
+{
+    PCIHostState *pci = PCI_HOST_BRIDGE(dev);
+
+    /*
+     * PHB3 doesn't support IO space. However, qemu gets very upset if
+     * we don't have an IO region to anchor IO BARs onto so we just
+     * initialize one which we never hook up to anything
+     */
+    memory_region_init(&phb->pci_io, OBJECT(phb), "pci-io", 0x10000);
+    memory_region_init(&phb->pci_mmio, OBJECT(phb), "pci-mmio",
+                       PCI_MMIO_TOTAL_SIZE);
+
+    pci->bus = pci_register_root_bus(dev,
+                                     dev->id ? dev->id : NULL,
+                                     pnv_phb3_set_irq, pnv_phb3_map_irq, phb,
+                                     &phb->pci_mmio, &phb->pci_io,
+                                     0, 4, TYPE_PNV_PHB3_ROOT_BUS);
+
+    pci_setup_iommu(pci->bus, pnv_phb3_dma_iommu, phb);
+}
+
 static void pnv_phb3_realize(DeviceState *dev, Error **errp)
 {
     PnvPHB3 *phb = PNV_PHB3(dev);
@@ -1035,22 +1057,7 @@ static void pnv_phb3_realize(DeviceState *dev, Error **errp)
     memory_region_init_io(&phb->mr_regs, OBJECT(phb), &pnv_phb3_reg_ops, phb,
                           "phb3-regs", 0x1000);
 
-    /*
-     * PHB3 doesn't support IO space. However, qemu gets very upset if
-     * we don't have an IO region to anchor IO BARs onto so we just
-     * initialize one which we never hook up to anything
-     */
-    memory_region_init(&phb->pci_io, OBJECT(phb), "pci-io", 0x10000);
-    memory_region_init(&phb->pci_mmio, OBJECT(phb), "pci-mmio",
-                       PCI_MMIO_TOTAL_SIZE);
-
-    pci->bus = pci_register_root_bus(dev,
-                                     dev->id ? dev->id : NULL,
-                                     pnv_phb3_set_irq, pnv_phb3_map_irq, phb,
-                                     &phb->pci_mmio, &phb->pci_io,
-                                     0, 4, TYPE_PNV_PHB3_ROOT_BUS);
-
-    pci_setup_iommu(pci->bus, pnv_phb3_dma_iommu, phb);
+    pnv_phb3_bus_init(dev, phb);
 
     pnv_phb_attach_root_port(pci, TYPE_PNV_PHB3_ROOT_PORT,
                              phb->phb_id, phb->chip_id);
diff --git a/include/hw/pci-host/pnv_phb3.h b/include/hw/pci-host/pnv_phb3.h
index af6ec83cf6..1375f18fc1 100644
--- a/include/hw/pci-host/pnv_phb3.h
+++ b/include/hw/pci-host/pnv_phb3.h
@@ -164,5 +164,6 @@ uint64_t pnv_phb3_reg_read(void *opaque, hwaddr off, unsigned size);
 void pnv_phb3_reg_write(void *opaque, hwaddr off, uint64_t val, unsigned size);
 void pnv_phb3_update_regions(PnvPHB3 *phb);
 void pnv_phb3_remap_irqs(PnvPHB3 *phb);
+void pnv_phb3_bus_init(DeviceState *dev, PnvPHB3 *phb);
 
 #endif /* PCI_HOST_PNV_PHB3_H */