Fixed MTP to work with TWRP

drivers/xen/xen-pciback/xenbus.c

@@ -0,0 +1,750 @@
+/*
+ * PCI Backend Xenbus Setup - handles setup with frontend and xend
+ *
+ *   Author: Ryan Wilson <hap9@epoch.ncsc.mil>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/vmalloc.h>
+#include <linux/workqueue.h>
+#include <xen/xenbus.h>
+#include <xen/events.h>
+#include <asm/xen/pci.h>
+#include "pciback.h"
+
+#define INVALID_EVTCHN_IRQ  (-1)
+struct workqueue_struct *xen_pcibk_wq;
+
+static bool __read_mostly passthrough;
+module_param(passthrough, bool, S_IRUGO);
+MODULE_PARM_DESC(passthrough,
+	"Option to specify how to export PCI topology to guest:\n"\
+	" 0 - (default) Hide the true PCI topology and makes the frontend\n"\
+	"   there is a single PCI bus with only the exported devices on it.\n"\
+	"   For example, a device at 03:05.0 will be re-assigned to 00:00.0\n"\
+	"   while second device at 02:1a.1 will be re-assigned to 00:01.1.\n"\
+	" 1 - Passthrough provides a real view of the PCI topology to the\n"\
+	"   frontend (for example, a device at 06:01.b will still appear at\n"\
+	"   06:01.b to the frontend). This is similar to how Xen 2.0.x\n"\
+	"   exposed PCI devices to its driver domains. This may be required\n"\
+	"   for drivers which depend on finding their hardward in certain\n"\
+	"   bus/slot locations.");
+
+static struct xen_pcibk_device *alloc_pdev(struct xenbus_device *xdev)
+{
+	struct xen_pcibk_device *pdev;
+
+	pdev = kzalloc(sizeof(struct xen_pcibk_device), GFP_KERNEL);
+	if (pdev == NULL)
+		goto out;
+	dev_dbg(&xdev->dev, "allocated pdev @ 0x%p\n", pdev);
+
+	pdev->xdev = xdev;
+	dev_set_drvdata(&xdev->dev, pdev);
+
+	mutex_init(&pdev->dev_lock);
+
+	pdev->sh_info = NULL;
+	pdev->evtchn_irq = INVALID_EVTCHN_IRQ;
+	pdev->be_watching = 0;
+
+	INIT_WORK(&pdev->op_work, xen_pcibk_do_op);
+
+	if (xen_pcibk_init_devices(pdev)) {
+		kfree(pdev);
+		pdev = NULL;
+	}
+out:
+	return pdev;
+}
+
+static void xen_pcibk_disconnect(struct xen_pcibk_device *pdev)
+{
+	mutex_lock(&pdev->dev_lock);
+	/* Ensure the guest can't trigger our handler before removing devices */
+	if (pdev->evtchn_irq != INVALID_EVTCHN_IRQ) {
+		unbind_from_irqhandler(pdev->evtchn_irq, pdev);
+		pdev->evtchn_irq = INVALID_EVTCHN_IRQ;
+	}
+
+	/* If the driver domain started an op, make sure we complete it
+	 * before releasing the shared memory */
+
+	/* Note, the workqueue does not use spinlocks at all.*/
+	flush_workqueue(xen_pcibk_wq);
+
+	if (pdev->sh_info != NULL) {
+		xenbus_unmap_ring_vfree(pdev->xdev, pdev->sh_info);
+		pdev->sh_info = NULL;
+	}
+	mutex_unlock(&pdev->dev_lock);
+}
+
+static void free_pdev(struct xen_pcibk_device *pdev)
+{
+	if (pdev->be_watching) {
+		unregister_xenbus_watch(&pdev->be_watch);
+		pdev->be_watching = 0;
+	}
+
+	xen_pcibk_disconnect(pdev);
+
+	/* N.B. This calls pcistub_put_pci_dev which does the FLR on all
+	 * of the PCIe devices. */
+	xen_pcibk_release_devices(pdev);
+
+	dev_set_drvdata(&pdev->xdev->dev, NULL);
+	pdev->xdev = NULL;
+
+	kfree(pdev);
+}
+
+static int xen_pcibk_do_attach(struct xen_pcibk_device *pdev, int gnt_ref,
+			     int remote_evtchn)
+{
+	int err = 0;
+	void *vaddr;
+
+	dev_dbg(&pdev->xdev->dev,
+		"Attaching to frontend resources - gnt_ref=%d evtchn=%d\n",
+		gnt_ref, remote_evtchn);
+
+	err = xenbus_map_ring_valloc(pdev->xdev, gnt_ref, &vaddr);
+	if (err < 0) {
+		xenbus_dev_fatal(pdev->xdev, err,
+				"Error mapping other domain page in ours.");
+		goto out;
+	}
+
+	pdev->sh_info = vaddr;
+
+	err = bind_interdomain_evtchn_to_irqhandler(
+		pdev->xdev->otherend_id, remote_evtchn, xen_pcibk_handle_event,
+		0, DRV_NAME, pdev);
+	if (err < 0) {
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error binding event channel to IRQ");
+		goto out;
+	}
+	pdev->evtchn_irq = err;
+	err = 0;
+
+	dev_dbg(&pdev->xdev->dev, "Attached!\n");
+out:
+	return err;
+}
+
+static int xen_pcibk_attach(struct xen_pcibk_device *pdev)
+{
+	int err = 0;
+	int gnt_ref, remote_evtchn;
+	char *magic = NULL;
+
+
+	mutex_lock(&pdev->dev_lock);
+	/* Make sure we only do this setup once */
+	if (xenbus_read_driver_state(pdev->xdev->nodename) !=
+	    XenbusStateInitialised)
+		goto out;
+
+	/* Wait for frontend to state that it has published the configuration */
+	if (xenbus_read_driver_state(pdev->xdev->otherend) !=
+	    XenbusStateInitialised)
+		goto out;
+
+	dev_dbg(&pdev->xdev->dev, "Reading frontend config\n");
+
+	err = xenbus_gather(XBT_NIL, pdev->xdev->otherend,
+			    "pci-op-ref", "%u", &gnt_ref,
+			    "event-channel", "%u", &remote_evtchn,
+			    "magic", NULL, &magic, NULL);
+	if (err) {
+		/* If configuration didn't get read correctly, wait longer */
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error reading configuration from frontend");
+		goto out;
+	}
+
+	if (magic == NULL || strcmp(magic, XEN_PCI_MAGIC) != 0) {
+		xenbus_dev_fatal(pdev->xdev, -EFAULT,
+				 "version mismatch (%s/%s) with pcifront - "
+				 "halting " DRV_NAME,
+				 magic, XEN_PCI_MAGIC);
+		err = -EFAULT;
+		goto out;
+	}
+
+	err = xen_pcibk_do_attach(pdev, gnt_ref, remote_evtchn);
+	if (err)
+		goto out;
+
+	dev_dbg(&pdev->xdev->dev, "Connecting...\n");
+
+	err = xenbus_switch_state(pdev->xdev, XenbusStateConnected);
+	if (err)
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error switching to connected state!");
+
+	dev_dbg(&pdev->xdev->dev, "Connected? %d\n", err);
+out:
+	mutex_unlock(&pdev->dev_lock);
+
+	kfree(magic);
+
+	return err;
+}
+
+static int xen_pcibk_publish_pci_dev(struct xen_pcibk_device *pdev,
+				   unsigned int domain, unsigned int bus,
+				   unsigned int devfn, unsigned int devid)
+{
+	int err;
+	int len;
+	char str[64];
+
+	len = snprintf(str, sizeof(str), "vdev-%d", devid);
+	if (unlikely(len >= (sizeof(str) - 1))) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	/* Note: The PV protocol uses %02x, don't change it */
+	err = xenbus_printf(XBT_NIL, pdev->xdev->nodename, str,
+			    "%04x:%02x:%02x.%02x", domain, bus,
+			    PCI_SLOT(devfn), PCI_FUNC(devfn));
+
+out:
+	return err;
+}
+
+static int xen_pcibk_export_device(struct xen_pcibk_device *pdev,
+				 int domain, int bus, int slot, int func,
+				 int devid)
+{
+	struct pci_dev *dev;
+	int err = 0;
+
+	dev_dbg(&pdev->xdev->dev, "exporting dom %x bus %x slot %x func %x\n",
+		domain, bus, slot, func);
+
+	dev = pcistub_get_pci_dev_by_slot(pdev, domain, bus, slot, func);
+	if (!dev) {
+		err = -EINVAL;
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Couldn't locate PCI device "
+				 "(%04x:%02x:%02x.%d)! "
+				 "perhaps already in-use?",
+				 domain, bus, slot, func);
+		goto out;
+	}
+
+	err = xen_pcibk_add_pci_dev(pdev, dev, devid,
+				    xen_pcibk_publish_pci_dev);
+	if (err)
+		goto out;
+
+	dev_dbg(&dev->dev, "registering for %d\n", pdev->xdev->otherend_id);
+	if (xen_register_device_domain_owner(dev,
+					     pdev->xdev->otherend_id) != 0) {
+		dev_err(&dev->dev, "Stealing ownership from dom%d.\n",
+			xen_find_device_domain_owner(dev));
+		xen_unregister_device_domain_owner(dev);
+		xen_register_device_domain_owner(dev, pdev->xdev->otherend_id);
+	}
+
+	/* TODO: It'd be nice to export a bridge and have all of its children
+	 * get exported with it. This may be best done in xend (which will
+	 * have to calculate resource usage anyway) but we probably want to
+	 * put something in here to ensure that if a bridge gets given to a
+	 * driver domain, that all devices under that bridge are not given
+	 * to other driver domains (as he who controls the bridge can disable
+	 * it and stop the other devices from working).
+	 */
+out:
+	return err;
+}
+
+static int xen_pcibk_remove_device(struct xen_pcibk_device *pdev,
+				 int domain, int bus, int slot, int func)
+{
+	int err = 0;
+	struct pci_dev *dev;
+
+	dev_dbg(&pdev->xdev->dev, "removing dom %x bus %x slot %x func %x\n",
+		domain, bus, slot, func);
+
+	dev = xen_pcibk_get_pci_dev(pdev, domain, bus, PCI_DEVFN(slot, func));
+	if (!dev) {
+		err = -EINVAL;
+		dev_dbg(&pdev->xdev->dev, "Couldn't locate PCI device "
+			"(%04x:%02x:%02x.%d)! not owned by this domain\n",
+			domain, bus, slot, func);
+		goto out;
+	}
+
+	dev_dbg(&dev->dev, "unregistering for %d\n", pdev->xdev->otherend_id);
+	xen_unregister_device_domain_owner(dev);
+
+	/* N.B. This ends up calling pcistub_put_pci_dev which ends up
+	 * doing the FLR. */
+	xen_pcibk_release_pci_dev(pdev, dev);
+
+out:
+	return err;
+}
+
+static int xen_pcibk_publish_pci_root(struct xen_pcibk_device *pdev,
+				    unsigned int domain, unsigned int bus)
+{
+	unsigned int d, b;
+	int i, root_num, len, err;
+	char str[64];
+
+	dev_dbg(&pdev->xdev->dev, "Publishing pci roots\n");
+
+	err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
+			   "root_num", "%d", &root_num);
+	if (err == 0 || err == -ENOENT)
+		root_num = 0;
+	else if (err < 0)
+		goto out;
+
+	/* Verify that we haven't already published this pci root */
+	for (i = 0; i < root_num; i++) {
+		len = snprintf(str, sizeof(str), "root-%d", i);
+		if (unlikely(len >= (sizeof(str) - 1))) {
+			err = -ENOMEM;
+			goto out;
+		}
+
+		err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
+				   str, "%x:%x", &d, &b);
+		if (err < 0)
+			goto out;
+		if (err != 2) {
+			err = -EINVAL;
+			goto out;
+		}
+
+		if (d == domain && b == bus) {
+			err = 0;
+			goto out;
+		}
+	}
+
+	len = snprintf(str, sizeof(str), "root-%d", root_num);
+	if (unlikely(len >= (sizeof(str) - 1))) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	dev_dbg(&pdev->xdev->dev, "writing root %d at %04x:%02x\n",
+		root_num, domain, bus);
+
+	err = xenbus_printf(XBT_NIL, pdev->xdev->nodename, str,
+			    "%04x:%02x", domain, bus);
+	if (err)
+		goto out;
+
+	err = xenbus_printf(XBT_NIL, pdev->xdev->nodename,
+			    "root_num", "%d", (root_num + 1));
+
+out:
+	return err;
+}
+
+static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev)
+{
+	int err = 0;
+	int num_devs;
+	int domain, bus, slot, func;
+	int substate;
+	int i, len;
+	char state_str[64];
+	char dev_str[64];
+
+
+	dev_dbg(&pdev->xdev->dev, "Reconfiguring device ...\n");
+
+	mutex_lock(&pdev->dev_lock);
+	/* Make sure we only reconfigure once */
+	if (xenbus_read_driver_state(pdev->xdev->nodename) !=
+	    XenbusStateReconfiguring)
+		goto out;
+
+	err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, "num_devs", "%d",
+			   &num_devs);
+	if (err != 1) {
+		if (err >= 0)
+			err = -EINVAL;
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error reading number of devices");
+		goto out;
+	}
+
+	for (i = 0; i < num_devs; i++) {
+		len = snprintf(state_str, sizeof(state_str), "state-%d", i);
+		if (unlikely(len >= (sizeof(state_str) - 1))) {
+			err = -ENOMEM;
+			xenbus_dev_fatal(pdev->xdev, err,
+					 "String overflow while reading "
+					 "configuration");
+			goto out;
+		}
+		err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, state_str,
+				   "%d", &substate);
+		if (err != 1)
+			substate = XenbusStateUnknown;
+
+		switch (substate) {
+		case XenbusStateInitialising:
+			dev_dbg(&pdev->xdev->dev, "Attaching dev-%d ...\n", i);
+
+			len = snprintf(dev_str, sizeof(dev_str), "dev-%d", i);
+			if (unlikely(len >= (sizeof(dev_str) - 1))) {
+				err = -ENOMEM;
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "String overflow while "
+						 "reading configuration");
+				goto out;
+			}
+			err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
+					   dev_str, "%x:%x:%x.%x",
+					   &domain, &bus, &slot, &func);
+			if (err < 0) {
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "Error reading device "
+						 "configuration");
+				goto out;
+			}
+			if (err != 4) {
+				err = -EINVAL;
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "Error parsing pci device "
+						 "configuration");
+				goto out;
+			}
+
+			err = xen_pcibk_export_device(pdev, domain, bus, slot,
+						    func, i);
+			if (err)
+				goto out;
+
+			/* Publish pci roots. */
+			err = xen_pcibk_publish_pci_roots(pdev,
+						xen_pcibk_publish_pci_root);
+			if (err) {
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "Error while publish PCI root"
+						 "buses for frontend");
+				goto out;
+			}
+
+			err = xenbus_printf(XBT_NIL, pdev->xdev->nodename,
+					    state_str, "%d",
+					    XenbusStateInitialised);
+			if (err) {
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "Error switching substate of "
+						 "dev-%d\n", i);
+				goto out;
+			}
+			break;
+
+		case XenbusStateClosing:
+			dev_dbg(&pdev->xdev->dev, "Detaching dev-%d ...\n", i);
+
+			len = snprintf(dev_str, sizeof(dev_str), "vdev-%d", i);
+			if (unlikely(len >= (sizeof(dev_str) - 1))) {
+				err = -ENOMEM;
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "String overflow while "
+						 "reading configuration");
+				goto out;
+			}
+			err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
+					   dev_str, "%x:%x:%x.%x",
+					   &domain, &bus, &slot, &func);
+			if (err < 0) {
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "Error reading device "
+						 "configuration");
+				goto out;
+			}
+			if (err != 4) {
+				err = -EINVAL;
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "Error parsing pci device "
+						 "configuration");
+				goto out;
+			}
+
+			err = xen_pcibk_remove_device(pdev, domain, bus, slot,
+						    func);
+			if (err)
+				goto out;
+
+			/* TODO: If at some point we implement support for pci
+			 * root hot-remove on pcifront side, we'll need to
+			 * remove unnecessary xenstore nodes of pci roots here.
+			 */
+
+			break;
+
+		default:
+			break;
+		}
+	}
+
+	err = xenbus_switch_state(pdev->xdev, XenbusStateReconfigured);
+	if (err) {
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error switching to reconfigured state!");
+		goto out;
+	}
+
+out:
+	mutex_unlock(&pdev->dev_lock);
+	return 0;
+}
+
+static void xen_pcibk_frontend_changed(struct xenbus_device *xdev,
+				     enum xenbus_state fe_state)
+{
+	struct xen_pcibk_device *pdev = dev_get_drvdata(&xdev->dev);
+
+	dev_dbg(&xdev->dev, "fe state changed %d\n", fe_state);
+
+	switch (fe_state) {
+	case XenbusStateInitialised:
+		xen_pcibk_attach(pdev);
+		break;
+
+	case XenbusStateReconfiguring:
+		xen_pcibk_reconfigure(pdev);
+		break;
+
+	case XenbusStateConnected:
+		/* pcifront switched its state from reconfiguring to connected.
+		 * Then switch to connected state.
+		 */
+		xenbus_switch_state(xdev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosing:
+		xen_pcibk_disconnect(pdev);
+		xenbus_switch_state(xdev, XenbusStateClosing);
+		break;
+
+	case XenbusStateClosed:
+		xen_pcibk_disconnect(pdev);
+		xenbus_switch_state(xdev, XenbusStateClosed);
+		if (xenbus_dev_is_online(xdev))
+			break;
+		/* fall through if not online */
+	case XenbusStateUnknown:
+		dev_dbg(&xdev->dev, "frontend is gone! unregister device\n");
+		device_unregister(&xdev->dev);
+		break;
+
+	default:
+		break;
+	}
+}
+
+static int xen_pcibk_setup_backend(struct xen_pcibk_device *pdev)
+{
+	/* Get configuration from xend (if available now) */
+	int domain, bus, slot, func;
+	int err = 0;
+	int i, num_devs;
+	char dev_str[64];
+	char state_str[64];
+
+	mutex_lock(&pdev->dev_lock);
+	/* It's possible we could get the call to setup twice, so make sure
+	 * we're not already connected.
+	 */
+	if (xenbus_read_driver_state(pdev->xdev->nodename) !=
+	    XenbusStateInitWait)
+		goto out;
+
+	dev_dbg(&pdev->xdev->dev, "getting be setup\n");
+
+	err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, "num_devs", "%d",
+			   &num_devs);
+	if (err != 1) {
+		if (err >= 0)
+			err = -EINVAL;
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error reading number of devices");
+		goto out;
+	}
+
+	for (i = 0; i < num_devs; i++) {
+		int l = snprintf(dev_str, sizeof(dev_str), "dev-%d", i);
+		if (unlikely(l >= (sizeof(dev_str) - 1))) {
+			err = -ENOMEM;
+			xenbus_dev_fatal(pdev->xdev, err,
+					 "String overflow while reading "
+					 "configuration");
+			goto out;
+		}
+
+		err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, dev_str,
+				   "%x:%x:%x.%x", &domain, &bus, &slot, &func);
+		if (err < 0) {
+			xenbus_dev_fatal(pdev->xdev, err,
+					 "Error reading device configuration");
+			goto out;
+		}
+		if (err != 4) {
+			err = -EINVAL;
+			xenbus_dev_fatal(pdev->xdev, err,
+					 "Error parsing pci device "
+					 "configuration");
+			goto out;
+		}
+
+		err = xen_pcibk_export_device(pdev, domain, bus, slot, func, i);
+		if (err)
+			goto out;
+
+		/* Switch substate of this device. */
+		l = snprintf(state_str, sizeof(state_str), "state-%d", i);
+		if (unlikely(l >= (sizeof(state_str) - 1))) {
+			err = -ENOMEM;
+			xenbus_dev_fatal(pdev->xdev, err,
+					 "String overflow while reading "
+					 "configuration");
+			goto out;
+		}
+		err = xenbus_printf(XBT_NIL, pdev->xdev->nodename, state_str,
+				    "%d", XenbusStateInitialised);
+		if (err) {
+			xenbus_dev_fatal(pdev->xdev, err, "Error switching "
+					 "substate of dev-%d\n", i);
+			goto out;
+		}
+	}
+
+	err = xen_pcibk_publish_pci_roots(pdev, xen_pcibk_publish_pci_root);
+	if (err) {
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error while publish PCI root buses "
+				 "for frontend");
+		goto out;
+	}
+
+	err = xenbus_switch_state(pdev->xdev, XenbusStateInitialised);
+	if (err)
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error switching to initialised state!");
+
+out:
+	mutex_unlock(&pdev->dev_lock);
+	if (!err)
+		/* see if pcifront is already configured (if not, we'll wait) */
+		xen_pcibk_attach(pdev);
+	return err;
+}
+
+static void xen_pcibk_be_watch(struct xenbus_watch *watch,
+			     const char **vec, unsigned int len)
+{
+	struct xen_pcibk_device *pdev =
+	    container_of(watch, struct xen_pcibk_device, be_watch);
+
+	switch (xenbus_read_driver_state(pdev->xdev->nodename)) {
+	case XenbusStateInitWait:
+		xen_pcibk_setup_backend(pdev);
+		break;
+
+	default:
+		break;
+	}
+}
+
+static int xen_pcibk_xenbus_probe(struct xenbus_device *dev,
+				const struct xenbus_device_id *id)
+{
+	int err = 0;
+	struct xen_pcibk_device *pdev = alloc_pdev(dev);
+
+	if (pdev == NULL) {
+		err = -ENOMEM;
+		xenbus_dev_fatal(dev, err,
+				 "Error allocating xen_pcibk_device struct");
+		goto out;
+	}
+
+	/* wait for xend to configure us */
+	err = xenbus_switch_state(dev, XenbusStateInitWait);
+	if (err)
+		goto out;
+
+	/* watch the backend node for backend configuration information */
+	err = xenbus_watch_path(dev, dev->nodename, &pdev->be_watch,
+				xen_pcibk_be_watch);
+	if (err)
+		goto out;
+
+	pdev->be_watching = 1;
+
+	/* We need to force a call to our callback here in case
+	 * xend already configured us!
+	 */
+	xen_pcibk_be_watch(&pdev->be_watch, NULL, 0);
+
+out:
+	return err;
+}
+
+static int xen_pcibk_xenbus_remove(struct xenbus_device *dev)
+{
+	struct xen_pcibk_device *pdev = dev_get_drvdata(&dev->dev);
+
+	if (pdev != NULL)
+		free_pdev(pdev);
+
+	return 0;
+}
+
+static const struct xenbus_device_id xen_pcibk_ids[] = {
+	{"pci"},
+	{""},
+};
+
+static struct xenbus_driver xen_pcibk_driver = {
+	.name                   = DRV_NAME,
+	.ids                    = xen_pcibk_ids,
+	.probe			= xen_pcibk_xenbus_probe,
+	.remove			= xen_pcibk_xenbus_remove,
+	.otherend_changed	= xen_pcibk_frontend_changed,
+};
+
+const struct xen_pcibk_backend *__read_mostly xen_pcibk_backend;
+
+int __init xen_pcibk_xenbus_register(void)
+{
+	xen_pcibk_wq = create_workqueue("xen_pciback_workqueue");
+	if (!xen_pcibk_wq) {
+		pr_err("%s: create xen_pciback_workqueue failed\n", __func__);
+		return -EFAULT;
+	}
+	xen_pcibk_backend = &xen_pcibk_vpci_backend;
+	if (passthrough)
+		xen_pcibk_backend = &xen_pcibk_passthrough_backend;
+	pr_info("backend is %s\n", xen_pcibk_backend->name);
+	return xenbus_register_backend(&xen_pcibk_driver);
+}
+
+void __exit xen_pcibk_xenbus_unregister(void)
+{
+	destroy_workqueue(xen_pcibk_wq);
+	xenbus_unregister_driver(&xen_pcibk_driver);
+}