diff --git a/sys/compat/linuxkpi/common/include/linux/device.h b/sys/compat/linuxkpi/common/include/linux/device.h
--- a/sys/compat/linuxkpi/common/include/linux/device.h
+++ b/sys/compat/linuxkpi/common/include/linux/device.h
@@ -451,9 +451,9 @@
 	dev->bsddev = NULL;
 
 	if (bsddev != NULL && dev->bsddev_attached_here) {
-		mtx_lock(&Giant);
+		bus_topo_lock();
 		device_delete_child(device_get_parent(bsddev), bsddev);
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 	}
 	put_device(dev);
 }
@@ -467,9 +467,9 @@
 	dev->bsddev = NULL;
 
 	if (bsddev != NULL && dev->bsddev_attached_here) {
-		mtx_lock(&Giant);
+		bus_topo_lock();
 		device_delete_child(device_get_parent(bsddev), bsddev);
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 	}
 }
 
diff --git a/sys/compat/linuxkpi/common/src/linux_pci.c b/sys/compat/linuxkpi/common/src/linux_pci.c
--- a/sys/compat/linuxkpi/common/src/linux_pci.c
+++ b/sys/compat/linuxkpi/common/src/linux_pci.c
@@ -710,10 +710,10 @@
 	pdrv->bsddriver.methods = pci_methods;
 	pdrv->bsddriver.size = sizeof(struct pci_dev);
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	error = devclass_add_driver(dc, &pdrv->bsddriver,
 	    BUS_PASS_DEFAULT, &pdrv->bsdclass);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	return (-error);
 }
 
@@ -882,10 +882,10 @@
 	spin_lock(&pci_lock);
 	list_del(&pdrv->node);
 	spin_unlock(&pci_lock);
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	if (bus != NULL)
 		devclass_delete_driver(bus, &pdrv->bsddriver);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 }
 
 void
@@ -898,10 +898,10 @@
 	spin_lock(&pci_lock);
 	list_del(&pdrv->node);
 	spin_unlock(&pci_lock);
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	if (bus != NULL)
 		devclass_delete_driver(bus, &pdrv->bsddriver);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 }
 
 int
diff --git a/sys/compat/linuxkpi/common/src/linux_usb.c b/sys/compat/linuxkpi/common/src/linux_usb.c
--- a/sys/compat/linuxkpi/common/src/linux_usb.c
+++ b/sys/compat/linuxkpi/common/src/linux_usb.c
@@ -1166,7 +1166,9 @@
 	LIST_FOREACH(sc, &usb_linux_attached_list, sc_attached_list) {
 		if (sc->sc_udrv == drv) {
 			mtx_unlock(&Giant);
+			bus_topo_lock();
 			device_detach(sc->sc_fbsd_dev);
+			bus_topo_unlock();
 			goto repeat;
 		}
 	}
diff --git a/sys/dev/aac/aac.c b/sys/dev/aac/aac.c
--- a/sys/dev/aac/aac.c
+++ b/sys/dev/aac/aac.c
@@ -3305,10 +3305,10 @@
 			while (co != NULL) {
 				if (co->co_found == 0) {
 					mtx_unlock(&sc->aac_io_lock);
-					mtx_lock(&Giant);
+					bus_topo_lock();
 					device_delete_child(sc->aac_dev,
 							    co->co_disk);
-					mtx_unlock(&Giant);
+					bus_topo_unlock();
 					mtx_lock(&sc->aac_io_lock);
 					co_next = TAILQ_NEXT(co, co_link);
 					mtx_lock(&sc->aac_container_lock);
@@ -3326,9 +3326,9 @@
 			/* Attach the newly created containers */
 			if (added) {
 				mtx_unlock(&sc->aac_io_lock);
-				mtx_lock(&Giant);
+				bus_topo_lock();
 				bus_generic_attach(sc->aac_dev);
-				mtx_unlock(&Giant);
+				bus_topo_unlock();
 				mtx_lock(&sc->aac_io_lock);
 			}
 
diff --git a/sys/dev/acpica/acpi.c b/sys/dev/acpica/acpi.c
--- a/sys/dev/acpica/acpi.c
+++ b/sys/dev/acpica/acpi.c
@@ -3258,10 +3258,9 @@
 #endif
 
     /*
-     * Be sure to hold Giant across DEVICE_SUSPEND/RESUME since non-MPSAFE
-     * drivers need this.
+     * Be sure to hold Giant across DEVICE_SUSPEND/RESUME
      */
-    mtx_lock(&Giant);
+    bus_topo_lock();
 
     slp_state = ACPI_SS_NONE;
 
@@ -3387,7 +3386,7 @@
     }
     sc->acpi_next_sstate = 0;
 
-    mtx_unlock(&Giant);
+    bus_topo_unlock();
 
 #ifdef EARLY_AP_STARTUP
     thread_lock(curthread);
diff --git a/sys/dev/acpica/acpi_dock.c b/sys/dev/acpica/acpi_dock.c
--- a/sys/dev/acpica/acpi_dock.c
+++ b/sys/dev/acpica/acpi_dock.c
@@ -193,9 +193,9 @@
 	if (!device_is_enabled(dev))
 		device_enable(dev);
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	device_probe_and_attach(dev);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 }
 
 static ACPI_STATUS
@@ -306,9 +306,9 @@
 
 	dev = acpi_get_device(handle);
 	if (dev != NULL && device_is_attached(dev)) {
-		mtx_lock(&Giant);
+		bus_topo_lock();
 		device_detach(dev);
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 	}
 
 	acpi_SetInteger(handle, "_EJ0", 0);
diff --git a/sys/dev/acpica/acpi_pci.c b/sys/dev/acpica/acpi_pci.c
--- a/sys/dev/acpica/acpi_pci.c
+++ b/sys/dev/acpica/acpi_pci.c
@@ -344,9 +344,9 @@
 
 	switch (notify) {
 	case ACPI_NOTIFY_BUS_CHECK:
-		mtx_lock(&Giant);
+		bus_topo_lock();
 		BUS_RESCAN(dev);
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 		break;
 	default:
 		device_printf(dev, "unknown notify %#x\n", notify);
@@ -365,9 +365,9 @@
 
 	switch (notify) {
 	case ACPI_NOTIFY_DEVICE_CHECK:
-		mtx_lock(&Giant);
+		bus_topo_lock();
 		BUS_RESCAN(dev);
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 		break;
 	case ACPI_NOTIFY_EJECT_REQUEST:
 		child = acpi_get_device(h);
@@ -376,23 +376,23 @@
 			    acpi_name(h));
 			return;
 		}
-		mtx_lock(&Giant);
+		bus_topo_lock();
 		error = device_detach(child);
 		if (error) {
-			mtx_unlock(&Giant);
+			bus_topo_unlock();
 			device_printf(dev, "failed to detach %s: %d\n",
 			    device_get_nameunit(child), error);
 			return;
 		}
 		status = acpi_SetInteger(h, "_EJ0", 1);
 		if (ACPI_FAILURE(status)) {
-			mtx_unlock(&Giant);
+			bus_topo_unlock();
 			device_printf(dev, "failed to eject %s: %s\n",
 			    acpi_name(h), AcpiFormatException(status));
 			return;
 		}
 		BUS_RESCAN(dev);
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 		break;
 	default:
 		device_printf(dev, "unknown notify %#x for %s\n", notify,
diff --git a/sys/dev/bhnd/cores/chipc/chipc.c b/sys/dev/bhnd/cores/chipc/chipc.c
--- a/sys/dev/bhnd/cores/chipc/chipc.c
+++ b/sys/dev/bhnd/cores/chipc/chipc.c
@@ -1164,13 +1164,13 @@
 	if (!CHIPC_QUIRK(sc, MUX_SPROM))
 		return (true);
 
-	mtx_lock(&Giant);	/* for newbus */
+	bus_topo_lock();
 
 	parent = device_get_parent(sc->dev);
 	hostb = bhnd_bus_find_hostb_device(parent);
 
 	if ((error = device_get_children(parent, &devs, &devcount))) {
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 		return (false);
 	}
 
@@ -1193,7 +1193,7 @@
 	}
 
 	free(devs, M_TEMP);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	return (result);
 }
 
diff --git a/sys/dev/cardbus/cardbus.c b/sys/dev/cardbus/cardbus.c
--- a/sys/dev/cardbus/cardbus.c
+++ b/sys/dev/cardbus/cardbus.c
@@ -199,7 +199,7 @@
 	domain = pcib_get_domain(cbdev);
 	bus = pcib_get_bus(cbdev);
 	slot = 0;
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	/* For each function, set it up and try to attach a driver to it */
 	for (func = 0; func <= cardbusfunchigh; func++) {
 		struct cardbus_devinfo *dinfo;
@@ -233,7 +233,7 @@
 		else
 			pci_cfg_save(dinfo->pci.cfg.dev, &dinfo->pci, 1);
 	}
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	if (cardattached > 0)
 		return (0);
 /*	POWER_DISABLE_SOCKET(brdev, cbdev); */
@@ -256,11 +256,11 @@
 {
 	int err = 0;
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	err = bus_generic_detach(cbdev);
 	if (err == 0)
 		err = device_delete_children(cbdev);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	if (err)
 		return (err);
 
diff --git a/sys/dev/drm2/drm_dp_iic_helper.c b/sys/dev/drm2/drm_dp_iic_helper.c
--- a/sys/dev/drm2/drm_dp_iic_helper.c
+++ b/sys/dev/drm2/drm_dp_iic_helper.c
@@ -228,12 +228,12 @@
 	int idx, error;
 	static int dp_bus_counter;
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 
 	idx = atomic_fetchadd_int(&dp_bus_counter, 1);
 	ibus = device_add_child(dev, "drm_iic_dp_aux", idx);
 	if (ibus == NULL) {
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 		DRM_ERROR("drm_iic_dp_aux bus %d creation error\n", idx);
 		return (-ENXIO);
 	}
@@ -241,7 +241,7 @@
 	error = device_probe_and_attach(ibus);
 	if (error != 0) {
 		device_delete_child(dev, ibus);
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 		DRM_ERROR("drm_iic_dp_aux bus %d attach failed, %d\n",
 		    idx, error);
 		return (-error);
@@ -256,7 +256,7 @@
 		*bus = ibus;
 		*adapter = data->port;
 	}
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	return (-error);
 }
 
diff --git a/sys/dev/hyperv/pcib/vmbus_pcib.c b/sys/dev/hyperv/pcib/vmbus_pcib.c
--- a/sys/dev/hyperv/pcib/vmbus_pcib.c
+++ b/sys/dev/hyperv/pcib/vmbus_pcib.c
@@ -560,14 +560,14 @@
 
 	devfn = wslot_to_devfn(hpdev->desc.wslot.val);
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 
 	pci_dev = pci_find_dbsf(hbus->pci_domain,
 	    0, PCI_SLOT(devfn), PCI_FUNC(devfn));
 	if (pci_dev)
 		device_delete_child(hbus->pci_bus, pci_dev);
 
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 
 	mtx_lock(&hbus->device_list_lock);
 	TAILQ_REMOVE(&hbus->children, hpdev, link);
diff --git a/sys/dev/ida/ida.c b/sys/dev/ida/ida.c
--- a/sys/dev/ida/ida.c
+++ b/sys/dev/ida/ida.c
@@ -334,9 +334,9 @@
 
 	config_intrhook_disestablish(&ida->ich);
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	bus_generic_attach(ida->dev);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 }
 
 int
diff --git a/sys/dev/mfi/mfi.c b/sys/dev/mfi/mfi.c
--- a/sys/dev/mfi/mfi.c
+++ b/sys/dev/mfi/mfi.c
@@ -1425,9 +1425,9 @@
 		if (found == 0) {
 			printf("DELETE\n");
 			mtx_unlock(&sc->mfi_io_lock);
-			mtx_lock(&Giant);
+			bus_topo_lock();
 			device_delete_child(sc->mfi_dev, syspd->pd_dev);
-			mtx_unlock(&Giant);
+			bus_topo_unlock();
 			mtx_lock(&sc->mfi_io_lock);
 		}
 	}
@@ -1585,9 +1585,9 @@
 			KASSERT(ld != NULL, ("volume dissappeared"));
 			*/
 			if (ld != NULL) {
-				mtx_lock(&Giant);
+				bus_topo_lock();
 				device_delete_child(sc->mfi_dev, ld->ld_dev);
-				mtx_unlock(&Giant);
+				bus_topo_unlock();
 			}
 		}
 		break;
@@ -1602,11 +1602,11 @@
 				    pd_link) {
 					if (syspd->pd_id ==
 					    detail->args.pd.device_id) {
-						mtx_lock(&Giant);
+						bus_topo_lock();
 						device_delete_child(
 						    sc->mfi_dev,
 						    syspd->pd_dev);
-						mtx_unlock(&Giant);
+						bus_topo_unlock();
 						break;
 					}
 				}
@@ -1923,11 +1923,11 @@
 	mfi_release_command(cm);
 
 	mtx_unlock(&sc->mfi_io_lock);
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	if ((child = device_add_child(sc->mfi_dev, "mfid", -1)) == NULL) {
 		device_printf(sc->mfi_dev, "Failed to add logical disk\n");
 		free(ld_info, M_MFIBUF);
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 		mtx_lock(&sc->mfi_io_lock);
 		return;
 	}
@@ -1935,7 +1935,7 @@
 	device_set_ivars(child, ld_info);
 	device_set_desc(child, "MFI Logical Disk");
 	bus_generic_attach(sc->mfi_dev);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	mtx_lock(&sc->mfi_io_lock);
 }
 
@@ -2011,11 +2011,11 @@
 	mfi_release_command(cm);
 
 	mtx_unlock(&sc->mfi_io_lock);
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	if ((child = device_add_child(sc->mfi_dev, "mfisyspd", -1)) == NULL) {
 		device_printf(sc->mfi_dev, "Failed to add system pd\n");
 		free(pd_info, M_MFIBUF);
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 		mtx_lock(&sc->mfi_io_lock);
 		return;
 	}
@@ -2023,7 +2023,7 @@
 	device_set_ivars(child, pd_info);
 	device_set_desc(child, "MFI System PD");
 	bus_generic_attach(sc->mfi_dev);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	mtx_lock(&sc->mfi_io_lock);
 }
 
@@ -2832,9 +2832,9 @@
 		KASSERT(ld != NULL, ("volume dissappeared"));
 		if (cm->cm_frame->header.cmd_status == MFI_STAT_OK) {
 			mtx_unlock(&sc->mfi_io_lock);
-			mtx_lock(&Giant);
+			bus_topo_lock();
 			device_delete_child(sc->mfi_dev, ld->ld_dev);
-			mtx_unlock(&Giant);
+			bus_topo_unlock();
 			mtx_lock(&sc->mfi_io_lock);
 		} else
 			mfi_disk_enable(ld);
@@ -2842,11 +2842,11 @@
 	case MFI_DCMD_CFG_CLEAR:
 		if (cm->cm_frame->header.cmd_status == MFI_STAT_OK) {
 			mtx_unlock(&sc->mfi_io_lock);
-			mtx_lock(&Giant);
+			bus_topo_lock();
 			TAILQ_FOREACH_SAFE(ld, &sc->mfi_ld_tqh, ld_link, ldn) {
 				device_delete_child(sc->mfi_dev, ld->ld_dev);
 			}
-			mtx_unlock(&Giant);
+			bus_topo_unlock();
 			mtx_lock(&sc->mfi_io_lock);
 		} else {
 			TAILQ_FOREACH(ld, &sc->mfi_ld_tqh, ld_link)
diff --git a/sys/dev/mfi/mfi_cam.c b/sys/dev/mfi/mfi_cam.c
--- a/sys/dev/mfi/mfi_cam.c
+++ b/sys/dev/mfi/mfi_cam.c
@@ -298,9 +298,9 @@
 	struct cam_sim *sim;
 	device_t mfip_dev;
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	mfip_dev = device_find_child(sc->mfi_dev, "mfip", -1);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	if (mfip_dev == NULL) {
 		device_printf(sc->mfi_dev, "Couldn't find mfip child device!\n");
 		return;
diff --git a/sys/dev/mlx/mlx.c b/sys/dev/mlx/mlx.c
--- a/sys/dev/mlx/mlx.c
+++ b/sys/dev/mlx/mlx.c
@@ -830,9 +830,9 @@
 	 * Scan the controller to see whether new drives have appeared.
 	 */
     case MLX_RESCAN_DRIVES:
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	mlx_startup(sc);
-	mtx_unlock(&Giant);	
+	bus_topo_unlock();
 	return(0);
 
 	/*
@@ -979,9 +979,9 @@
     case MLX_GET_SYSDRIVE:
 	error = ENOENT;
 	MLX_CONFIG_LOCK(sc);
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	mlxd = (struct mlxd_softc *)devclass_get_softc(mlxd_devclass, *arg);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	if ((mlxd != NULL) && (mlxd->mlxd_drive >= sc->mlx_sysdrive) && 
 	    (mlxd->mlxd_drive < (sc->mlx_sysdrive + MLX_MAXDRIVES))) {
 	    error = 0;
diff --git a/sys/dev/mlx5/mlx5_core/mlx5_fwdump.c b/sys/dev/mlx5/mlx5_core/mlx5_fwdump.c
--- a/sys/dev/mlx5/mlx5_core/mlx5_fwdump.c
+++ b/sys/dev/mlx5/mlx5_core/mlx5_fwdump.c
@@ -343,11 +343,11 @@
 	error = -mlx5_set_mfrl_reg(mdev, MLX5_FRL_LEVEL3);
 	if (error == 0) {
 		dev = mdev->pdev->dev.bsddev;
-		mtx_lock(&Giant);
+		bus_topo_lock();
 		bus = device_get_parent(dev);
 		error = BUS_RESET_CHILD(device_get_parent(bus), bus,
 		    DEVF_RESET_DETACH);
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 	}
 	return (error);
 }
diff --git a/sys/dev/mlx5/mlx5_core/mlx5_health.c b/sys/dev/mlx5/mlx5_core/mlx5_health.c
--- a/sys/dev/mlx5/mlx5_core/mlx5_health.c
+++ b/sys/dev/mlx5/mlx5_core/mlx5_health.c
@@ -377,7 +377,8 @@
 	priv = container_of(health, struct mlx5_priv, health);
 	dev = container_of(priv, struct mlx5_core_dev, priv);
 
-	mtx_lock(&Giant);	/* XXX newbus needs this */
+	/* This might likely be wrong, cut and paste from elsewhere? */
+	bus_topo_lock();
 
 	if (sensor_pci_no_comm(dev)) {
 		mlx5_core_err(dev,
@@ -404,7 +405,7 @@
 		mlx5_recover_device(dev);
 	}
 
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 }
 
 /* How much time to wait until health resetting the driver (in msecs) */
diff --git a/sys/dev/pccard/pccard.c b/sys/dev/pccard/pccard.c
--- a/sys/dev/pccard/pccard.c
+++ b/sys/dev/pccard/pccard.c
@@ -238,7 +238,7 @@
 	DEVPRINTF((dev, "Card has %d functions. pccard_mfc is %d\n", i + 1,
 	    pccard_mfc(sc)));
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	STAILQ_FOREACH(pf, &sc->card.pf_head, pf_list) {
 		if (STAILQ_EMPTY(&pf->cfe_head))
 			continue;
@@ -251,7 +251,7 @@
 		pf->dev = child;
 		pccard_probe_and_attach_child(dev, child, pf);
 	}
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	return (0);
 }
 
diff --git a/sys/dev/pci/pci_pci.c b/sys/dev/pci/pci_pci.c
--- a/sys/dev/pci/pci_pci.c
+++ b/sys/dev/pci/pci_pci.c
@@ -1397,7 +1397,7 @@
 	    pcib_pcie_cc_timeout, sc);
 	TIMEOUT_TASK_INIT(taskqueue_pci_hp, &sc->pcie_dll_task, 0,
 	    pcib_pcie_dll_timeout, sc);
-	sc->pcie_hp_lock = &Giant;
+	sc->pcie_hp_lock = bus_topo_mtx();
 
 	/* Allocate IRQ. */
 	if (pcib_alloc_pcie_irq(sc) != 0)
diff --git a/sys/dev/pci/pci_user.c b/sys/dev/pci/pci_user.c
--- a/sys/dev/pci/pci_user.c
+++ b/sys/dev/pci/pci_user.c
@@ -1056,8 +1056,11 @@
 		}
 	}
 
-	/* Giant because newbus is Giant locked revisit with newbus locking */
-	mtx_lock(&Giant);
+	/*
+	 * Use bus topology lock to ensure that the pci list of devies doesn't
+	 * change while we're traversing the list, in some cases multiple times.
+	 */
+	bus_topo_lock();
 
 	switch (cmd) {
 	case PCIOCGETCONF:
@@ -1409,7 +1412,7 @@
 		break;
 	}
 
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 
 	return (error);
 }
diff --git a/sys/dev/sdio/sdiob.c b/sys/dev/sdio/sdiob.c
--- a/sys/dev/sdio/sdiob.c
+++ b/sys/dev/sdio/sdiob.c
@@ -947,10 +947,10 @@
 		return (ENXIO);
 	}
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	error = devclass_add_driver(bus_devclass, &sdiob_driver,
 	    BUS_PASS_DEFAULT, &sdiob_devclass);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	if (error != 0) {
 		printf("%s: Failed to add driver to devclass: %d.\n",
 		    __func__, error);
diff --git a/sys/dev/twe/twe_freebsd.c b/sys/dev/twe/twe_freebsd.c
--- a/sys/dev/twe/twe_freebsd.c
+++ b/sys/dev/twe/twe_freebsd.c
@@ -583,10 +583,10 @@
     char	buf[80];
     int		error;
 
-    mtx_lock(&Giant);
+    bus_topo_lock();
     dr->td_disk =  device_add_child(sc->twe_dev, NULL, -1);
     if (dr->td_disk == NULL) {
-	mtx_unlock(&Giant);
+	    bus_topo_unlock();
 	twe_printf(sc, "Cannot add unit\n");
 	return (EIO);
     }
@@ -603,7 +603,7 @@
     device_set_desc_copy(dr->td_disk, buf);
 
     error = device_probe_and_attach(dr->td_disk);
-    mtx_unlock(&Giant);
+    bus_topo_unlock();
     if (error != 0) {
 	twe_printf(sc, "Cannot attach unit to controller. error = %d\n", error);
 	return (EIO);
@@ -622,9 +622,9 @@
     int error = 0;
 
     TWE_CONFIG_ASSERT_LOCKED(sc);
-    mtx_lock(&Giant);
+    bus_topo_lock();
     error = device_delete_child(sc->twe_dev, sc->twe_drive[unit].td_disk);
-    mtx_unlock(&Giant);
+    bus_topo_unlock();
     if (error != 0) {
 	twe_printf(sc, "failed to delete unit %d\n", unit);
 	return(error);
diff --git a/sys/dev/usb/controller/usb_controller.c b/sys/dev/usb/controller/usb_controller.c
--- a/sys/dev/usb/controller/usb_controller.c
+++ b/sys/dev/usb/controller/usb_controller.c
@@ -438,9 +438,9 @@
 	USB_BUS_UNLOCK(bus);
 
 	/* detach children first */
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	bus_generic_detach(dev);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 
 	/*
 	 * Free USB device and all subdevices, if any.
@@ -803,10 +803,10 @@
 static void
 usb_attach_sub(device_t dev, struct usb_bus *bus)
 {
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	if (usb_devclass_ptr == NULL)
 		usb_devclass_ptr = devclass_find("usbus");
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 
 #if USB_HAVE_PF
 	usbpf_attach(bus);
diff --git a/sys/dev/usb/net/if_axe.c b/sys/dev/usb/net/if_axe.c
--- a/sys/dev/usb/net/if_axe.c
+++ b/sys/dev/usb/net/if_axe.c
@@ -901,11 +901,11 @@
 		adv_pause = MIIF_DOPAUSE;
 	else
 		adv_pause = 0;
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	error = mii_attach(ue->ue_dev, &ue->ue_miibus, ifp,
 	    uether_ifmedia_upd, ue->ue_methods->ue_mii_sts,
 	    BMSR_DEFCAPMASK, sc->sc_phyno, MII_OFFSET_ANY, adv_pause);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 
 	return (error);
 }
diff --git a/sys/dev/usb/net/if_axge.c b/sys/dev/usb/net/if_axge.c
--- a/sys/dev/usb/net/if_axge.c
+++ b/sys/dev/usb/net/if_axge.c
@@ -468,11 +468,11 @@
 	ifp->if_hwassist = AXGE_CSUM_FEATURES;
 	ifp->if_capenable = ifp->if_capabilities;
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	error = mii_attach(ue->ue_dev, &ue->ue_miibus, ifp,
 	    uether_ifmedia_upd, ue->ue_methods->ue_mii_sts,
 	    BMSR_DEFCAPMASK, AXGE_PHY_ADDR, MII_OFFSET_ANY, MIIF_DOPAUSE);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 
 	return (error);
 }
diff --git a/sys/dev/usb/net/if_muge.c b/sys/dev/usb/net/if_muge.c
--- a/sys/dev/usb/net/if_muge.c
+++ b/sys/dev/usb/net/if_muge.c
@@ -1638,11 +1638,11 @@
 
 	ifp->if_capenable = ifp->if_capabilities;
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	error = mii_attach(ue->ue_dev, &ue->ue_miibus, ifp, uether_ifmedia_upd,
 	    ue->ue_methods->ue_mii_sts, BMSR_DEFCAPMASK, sc->sc_phyno,
 	    MII_OFFSET_ANY, 0);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 
 	return (0);
 }
diff --git a/sys/dev/usb/net/if_smsc.c b/sys/dev/usb/net/if_smsc.c
--- a/sys/dev/usb/net/if_smsc.c
+++ b/sys/dev/usb/net/if_smsc.c
@@ -1641,11 +1641,11 @@
 
 	ifp->if_capenable = ifp->if_capabilities;
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	error = mii_attach(ue->ue_dev, &ue->ue_miibus, ifp,
 	    uether_ifmedia_upd, ue->ue_methods->ue_mii_sts,
 	    BMSR_DEFCAPMASK, sc->sc_phyno, MII_OFFSET_ANY, 0);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 
 	return (error);
 }
diff --git a/sys/dev/usb/net/if_ure.c b/sys/dev/usb/net/if_ure.c
--- a/sys/dev/usb/net/if_ure.c
+++ b/sys/dev/usb/net/if_ure.c
@@ -1014,7 +1014,6 @@
 #endif
 	if_setcapenable(ifp, if_getcapabilities(ifp));
 
-	mtx_lock(&Giant);
 	if (sc->sc_flags & (URE_FLAG_8156 | URE_FLAG_8156B)) {
 		ifmedia_init(&sc->sc_ifmedia, IFM_IMASK, ure_ifmedia_upd,
 		    ure_ifmedia_sts);
@@ -1024,11 +1023,12 @@
 		sc->sc_ifmedia.ifm_media = IFM_ETHER | IFM_AUTO;
 		error = 0;
 	} else {
+		bus_topo_lock();
 		error = mii_attach(ue->ue_dev, &ue->ue_miibus, ifp,
 		    uether_ifmedia_upd, ue->ue_methods->ue_mii_sts,
 		    BMSR_DEFCAPMASK, sc->sc_phyno, MII_OFFSET_ANY, 0);
+		bus_topo_unlock();
 	}
-	mtx_unlock(&Giant);
 
 	sctx = device_get_sysctl_ctx(sc->sc_ue.ue_dev);
 	soid = device_get_sysctl_tree(sc->sc_ue.ue_dev);
diff --git a/sys/dev/usb/net/usb_ethernet.c b/sys/dev/usb/net/usb_ethernet.c
--- a/sys/dev/usb/net/usb_ethernet.c
+++ b/sys/dev/usb/net/usb_ethernet.c
@@ -249,12 +249,11 @@
 
 		if (ue->ue_methods->ue_mii_upd != NULL &&
 		    ue->ue_methods->ue_mii_sts != NULL) {
-			/* device_xxx() depends on this */
-			mtx_lock(&Giant);
+			bus_topo_lock();
 			error = mii_attach(ue->ue_dev, &ue->ue_miibus, ifp,
 			    ue_ifmedia_upd, ue->ue_methods->ue_mii_sts,
 			    BMSR_DEFCAPMASK, MII_PHY_ANY, MII_OFFSET_ANY, 0);
-			mtx_unlock(&Giant);
+			bus_topo_unlock();
 		}
 	}
 
@@ -327,9 +326,9 @@
 
 		/* detach miibus */
 		if (ue->ue_miibus != NULL) {
-			mtx_lock(&Giant);	/* device_xxx() depends on this */
+			bus_topo_lock();
 			device_delete_child(ue->ue_dev, ue->ue_miibus);
-			mtx_unlock(&Giant);
+			bus_topo_unlock();
 		}
 
 		/* free interface instance */
diff --git a/sys/dev/usb/usb_device.c b/sys/dev/usb/usb_device.c
--- a/sys/dev/usb/usb_device.c
+++ b/sys/dev/usb/usb_device.c
@@ -2905,7 +2905,7 @@
 	 * are locked before locking Giant. Else the lock can be
 	 * locked multiple times.
 	 */
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	return (1);
 }
 
@@ -2925,7 +2925,7 @@
 		sx_xunlock(&udev->enum_sx);
 		return (255);
 	}
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	return (1);
 }
 #endif
@@ -2935,7 +2935,7 @@
 void
 usbd_enum_unlock(struct usb_device *udev)
 {
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	sx_xunlock(&udev->enum_sx);
 	sx_xunlock(&udev->sr_sx);
 }
@@ -2951,7 +2951,7 @@
 	 * are locked before locking Giant. Else the lock can be
 	 * locked multiple times.
 	 */
-	mtx_lock(&Giant);
+	bus_topo_lock();
 }
 
 /* The following function unlocks suspend and resume. */
@@ -2959,7 +2959,7 @@
 void
 usbd_sr_unlock(struct usb_device *udev)
 {
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	sx_xunlock(&udev->sr_sx);
 }
 
diff --git a/sys/dev/xen/control/control.c b/sys/dev/xen/control/control.c
--- a/sys/dev/xen/control/control.c
+++ b/sys/dev/xen/control/control.c
@@ -223,12 +223,11 @@
 	KASSERT((PCPU_GET(cpuid) == 0), ("Not running on CPU#0"));
 
 	/*
-	 * Be sure to hold Giant across DEVICE_SUSPEND/RESUME since non-MPSAFE
-	 * drivers need this.
+	 * Be sure to hold Giant across DEVICE_SUSPEND/RESUME.
 	 */
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	if (DEVICE_SUSPEND(root_bus) != 0) {
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 		printf("%s: device_suspend failed\n", __func__);
 		return;
 	}
@@ -299,7 +298,7 @@
 	 * similar.
 	 */
 	DEVICE_RESUME(root_bus);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 
 	/*
 	 * Warm up timecounter again and reset system clock.
diff --git a/sys/kern/subr_bus.c b/sys/kern/subr_bus.c
--- a/sys/kern/subr_bus.c
+++ b/sys/kern/subr_bus.c
@@ -865,6 +865,27 @@
 
 DEFINE_CLASS(null, null_methods, 0);
 
+struct mtx *
+bus_topo_mtx(void)
+{
+
+	return (&Giant);
+}
+
+void
+bus_topo_lock(void)
+{
+
+	mtx_lock(bus_topo_mtx());
+}
+
+void
+bus_topo_unlock(void)
+{
+
+	mtx_unlock(bus_topo_mtx());
+}
+
 /*
  * Bus pass implementation
  */
@@ -5725,7 +5746,7 @@
 	int error, old;
 
 	/* Locate the device to control. */
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	req = (struct devreq *)data;
 	switch (cmd) {
 	case DEV_ATTACH:
@@ -5752,7 +5773,7 @@
 		break;
 	}
 	if (error) {
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 		return (error);
 	}
 
@@ -5973,7 +5994,7 @@
 		    req->dr_flags);
 		break;
 	}
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	return (error);
 }
 
diff --git a/sys/net/iflib_clone.c b/sys/net/iflib_clone.c
--- a/sys/net/iflib_clone.c
+++ b/sys/net/iflib_clone.c
@@ -181,9 +181,9 @@
 
 	if (__predict_false(iflib_pseudodev == NULL)) {
 		/* SYSINIT initialization would panic !?! */
-		mtx_lock(&Giant);
+		bus_topo_lock();
 		iflib_pseudodev = device_add_child(root_bus, "ifpseudo", 0);
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 		MPASS(iflib_pseudodev != NULL);
 	}
 	ip = iflib_ip_lookup(name);
@@ -207,9 +207,9 @@
 	MPASS(devclass_get_device(ip->ip_dc, unit) == dev);
 	rc = iflib_pseudo_register(dev, ip->ip_sctx, &ctx, &clctx);
 	if (rc) {
-		mtx_lock(&Giant);
+		bus_topo_lock();
 		device_delete_child(iflib_pseudodev, dev);
-		mtx_unlock(&Giant);
+		bus_topo_unlock();
 	} else
 		device_set_softc(dev, ctx);
 
@@ -235,9 +235,9 @@
 	iflib_stop(ctx);
 	sx_xunlock(ctx_lock);
 
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	rc = device_delete_child(iflib_pseudodev, dev);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 	if (rc == 0)
 		iflib_pseudo_deregister(ctx);
 }
diff --git a/sys/sys/bus.h b/sys/sys/bus.h
--- a/sys/sys/bus.h
+++ b/sys/sys/bus.h
@@ -751,6 +751,14 @@
 
 void	bus_set_pass(int pass);
 
+/**
+ * Routines to lock / unlock the newbus lock.
+ * Must be taken out to interact with newbus.
+ */
+void bus_topo_lock(void);
+void bus_topo_unlock(void);
+struct mtx * bus_topo_mtx(void);
+
 /**
  * Shorthands for constructing method tables.
  */
@@ -784,7 +792,7 @@
 
 #define	_EARLY_DRIVER_MODULE_ORDERED(name, busname, driver, devclass,	\
     evh, arg, order, pass)						\
-									\
+								\
 static struct driver_module_data name##_##busname##_driver_mod = {	\
 	evh, arg,							\
 	#busname,							\
diff --git a/sys/xen/xenbus/xenbusb.c b/sys/xen/xenbus/xenbusb.c
--- a/sys/xen/xenbus/xenbusb.c
+++ b/sys/xen/xenbus/xenbusb.c
@@ -533,12 +533,9 @@
 {
 	device_t dev = (device_t)arg;
 
-	/*
-	 * Hold Giant until the Giant free newbus changes are committed.
-	 */
-	mtx_lock(&Giant);
+	bus_topo_lock();
 	xenbusb_probe_children(dev);
-	mtx_unlock(&Giant);
+	bus_topo_unlock();
 }
 
 /**