diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 5fb6c4c4c6..83fe329474 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -2957,6 +2957,99 @@ static void vfio_unregister_req_notifier(VFIOPCIDevice *vdev)
     vdev->req_enabled = false;
 }
 
+static bool vfio_pci_config_setup(VFIOPCIDevice *vdev, Error **errp)
+{
+    PCIDevice *pdev = &vdev->pdev;
+    VFIODevice *vbasedev = &vdev->vbasedev;
+
+    /* vfio emulates a lot for us, but some bits need extra love */
+    vdev->emulated_config_bits = g_malloc0(vdev->config_size);
+
+    /* QEMU can choose to expose the ROM or not */
+    memset(vdev->emulated_config_bits + PCI_ROM_ADDRESS, 0xff, 4);
+    /* QEMU can also add or extend BARs */
+    memset(vdev->emulated_config_bits + PCI_BASE_ADDRESS_0, 0xff, 6 * 4);
+
+    /*
+     * The PCI spec reserves vendor ID 0xffff as an invalid value.  The
+     * device ID is managed by the vendor and need only be a 16-bit value.
+     * Allow any 16-bit value for subsystem so they can be hidden or changed.
+     */
+    if (vdev->vendor_id != PCI_ANY_ID) {
+        if (vdev->vendor_id >= 0xffff) {
+            error_setg(errp, "invalid PCI vendor ID provided");
+            return false;
+        }
+        vfio_add_emulated_word(vdev, PCI_VENDOR_ID, vdev->vendor_id, ~0);
+        trace_vfio_pci_emulated_vendor_id(vbasedev->name, vdev->vendor_id);
+    } else {
+        vdev->vendor_id = pci_get_word(pdev->config + PCI_VENDOR_ID);
+    }
+
+    if (vdev->device_id != PCI_ANY_ID) {
+        if (vdev->device_id > 0xffff) {
+            error_setg(errp, "invalid PCI device ID provided");
+            return false;
+        }
+        vfio_add_emulated_word(vdev, PCI_DEVICE_ID, vdev->device_id, ~0);
+        trace_vfio_pci_emulated_device_id(vbasedev->name, vdev->device_id);
+    } else {
+        vdev->device_id = pci_get_word(pdev->config + PCI_DEVICE_ID);
+    }
+
+    if (vdev->sub_vendor_id != PCI_ANY_ID) {
+        if (vdev->sub_vendor_id > 0xffff) {
+            error_setg(errp, "invalid PCI subsystem vendor ID provided");
+            return false;
+        }
+        vfio_add_emulated_word(vdev, PCI_SUBSYSTEM_VENDOR_ID,
+                               vdev->sub_vendor_id, ~0);
+        trace_vfio_pci_emulated_sub_vendor_id(vbasedev->name,
+                                              vdev->sub_vendor_id);
+    }
+
+    if (vdev->sub_device_id != PCI_ANY_ID) {
+        if (vdev->sub_device_id > 0xffff) {
+            error_setg(errp, "invalid PCI subsystem device ID provided");
+            return false;
+        }
+        vfio_add_emulated_word(vdev, PCI_SUBSYSTEM_ID, vdev->sub_device_id, ~0);
+        trace_vfio_pci_emulated_sub_device_id(vbasedev->name,
+                                              vdev->sub_device_id);
+    }
+
+    /* QEMU can change multi-function devices to single function, or reverse */
+    vdev->emulated_config_bits[PCI_HEADER_TYPE] =
+                                              PCI_HEADER_TYPE_MULTI_FUNCTION;
+
+    /* Restore or clear multifunction, this is always controlled by QEMU */
+    if (vdev->pdev.cap_present & QEMU_PCI_CAP_MULTIFUNCTION) {
+        vdev->pdev.config[PCI_HEADER_TYPE] |= PCI_HEADER_TYPE_MULTI_FUNCTION;
+    } else {
+        vdev->pdev.config[PCI_HEADER_TYPE] &= ~PCI_HEADER_TYPE_MULTI_FUNCTION;
+    }
+
+    /*
+     * Clear host resource mapping info.  If we choose not to register a
+     * BAR, such as might be the case with the option ROM, we can get
+     * confusing, unwritable, residual addresses from the host here.
+     */
+    memset(&vdev->pdev.config[PCI_BASE_ADDRESS_0], 0, 24);
+    memset(&vdev->pdev.config[PCI_ROM_ADDRESS], 0, 4);
+
+    vfio_pci_size_rom(vdev);
+
+    vfio_bars_prepare(vdev);
+
+    if (!vfio_msix_early_setup(vdev, errp)) {
+        return false;
+    }
+
+    vfio_bars_register(vdev);
+
+    return true;
+}
+
 static bool vfio_interrupt_setup(VFIOPCIDevice *vdev, Error **errp)
 {
     PCIDevice *pdev = &vdev->pdev;
@@ -3060,91 +3153,10 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
         goto error;
     }
 
-    /* vfio emulates a lot for us, but some bits need extra love */
-    vdev->emulated_config_bits = g_malloc0(vdev->config_size);
-
-    /* QEMU can choose to expose the ROM or not */
-    memset(vdev->emulated_config_bits + PCI_ROM_ADDRESS, 0xff, 4);
-    /* QEMU can also add or extend BARs */
-    memset(vdev->emulated_config_bits + PCI_BASE_ADDRESS_0, 0xff, 6 * 4);
-
-    /*
-     * The PCI spec reserves vendor ID 0xffff as an invalid value.  The
-     * device ID is managed by the vendor and need only be a 16-bit value.
-     * Allow any 16-bit value for subsystem so they can be hidden or changed.
-     */
-    if (vdev->vendor_id != PCI_ANY_ID) {
-        if (vdev->vendor_id >= 0xffff) {
-            error_setg(errp, "invalid PCI vendor ID provided");
-            goto error;
-        }
-        vfio_add_emulated_word(vdev, PCI_VENDOR_ID, vdev->vendor_id, ~0);
-        trace_vfio_pci_emulated_vendor_id(vbasedev->name, vdev->vendor_id);
-    } else {
-        vdev->vendor_id = pci_get_word(pdev->config + PCI_VENDOR_ID);
-    }
-
-    if (vdev->device_id != PCI_ANY_ID) {
-        if (vdev->device_id > 0xffff) {
-            error_setg(errp, "invalid PCI device ID provided");
-            goto error;
-        }
-        vfio_add_emulated_word(vdev, PCI_DEVICE_ID, vdev->device_id, ~0);
-        trace_vfio_pci_emulated_device_id(vbasedev->name, vdev->device_id);
-    } else {
-        vdev->device_id = pci_get_word(pdev->config + PCI_DEVICE_ID);
-    }
-
-    if (vdev->sub_vendor_id != PCI_ANY_ID) {
-        if (vdev->sub_vendor_id > 0xffff) {
-            error_setg(errp, "invalid PCI subsystem vendor ID provided");
-            goto error;
-        }
-        vfio_add_emulated_word(vdev, PCI_SUBSYSTEM_VENDOR_ID,
-                               vdev->sub_vendor_id, ~0);
-        trace_vfio_pci_emulated_sub_vendor_id(vbasedev->name,
-                                              vdev->sub_vendor_id);
-    }
-
-    if (vdev->sub_device_id != PCI_ANY_ID) {
-        if (vdev->sub_device_id > 0xffff) {
-            error_setg(errp, "invalid PCI subsystem device ID provided");
-            goto error;
-        }
-        vfio_add_emulated_word(vdev, PCI_SUBSYSTEM_ID, vdev->sub_device_id, ~0);
-        trace_vfio_pci_emulated_sub_device_id(vbasedev->name,
-                                              vdev->sub_device_id);
-    }
-
-    /* QEMU can change multi-function devices to single function, or reverse */
-    vdev->emulated_config_bits[PCI_HEADER_TYPE] =
-                                              PCI_HEADER_TYPE_MULTI_FUNCTION;
-
-    /* Restore or clear multifunction, this is always controlled by QEMU */
-    if (vdev->pdev.cap_present & QEMU_PCI_CAP_MULTIFUNCTION) {
-        vdev->pdev.config[PCI_HEADER_TYPE] |= PCI_HEADER_TYPE_MULTI_FUNCTION;
-    } else {
-        vdev->pdev.config[PCI_HEADER_TYPE] &= ~PCI_HEADER_TYPE_MULTI_FUNCTION;
-    }
-
-    /*
-     * Clear host resource mapping info.  If we choose not to register a
-     * BAR, such as might be the case with the option ROM, we can get
-     * confusing, unwritable, residual addresses from the host here.
-     */
-    memset(&vdev->pdev.config[PCI_BASE_ADDRESS_0], 0, 24);
-    memset(&vdev->pdev.config[PCI_ROM_ADDRESS], 0, 4);
-
-    vfio_pci_size_rom(vdev);
-
-    vfio_bars_prepare(vdev);
-
-    if (!vfio_msix_early_setup(vdev, errp)) {
+    if (!vfio_pci_config_setup(vdev, errp)) {
         goto error;
     }
 
-    vfio_bars_register(vdev);
-
     if (!vbasedev->mdev &&
         !pci_device_set_iommu_device(pdev, vbasedev->hiod, errp)) {
         error_prepend(errp, "Failed to set vIOMMU: ");
