1 files changed, 768 insertions, 0 deletions

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
new file mode 100644
index 000000000000..34570823355b
--- /dev/null
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -0,0 +1,768 @@
+/*  Xenbus code for blkif backend
+    Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
+    Copyright (C) 2005 XenSource Ltd
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+*/
+
+#include <stdarg.h>
+#include <linux/module.h>
+#include <linux/kthread.h>
+#include <xen/events.h>
+#include <xen/grant_table.h>
+#include "common.h"
+
+struct backend_info {
+        struct xenbus_device    *dev;
+        struct xen_blkif        *blkif;
+        struct xenbus_watch     backend_watch;
+        unsigned                major;
+        unsigned                minor;
+        char                    *mode;
+};
+
+static struct kmem_cache *xen_blkif_cachep;
+static void connect(struct backend_info *);
+static int connect_ring(struct backend_info *);
+static void backend_changed(struct xenbus_watch *, const char **,
+                            unsigned int);
+
+struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be)
+{
+        return be->dev;
+}
+
+static int blkback_name(struct xen_blkif *blkif, char *buf)
+{
+        char *devpath, *devname;
+        struct xenbus_device *dev = blkif->be->dev;
+
+        devpath = xenbus_read(XBT_NIL, dev->nodename, "dev", NULL);
+        if (IS_ERR(devpath))
+                return PTR_ERR(devpath);
+
+        devname = strstr(devpath, "/dev/");
+        if (devname != NULL)
+                devname += strlen("/dev/");
+        else
+                devname  = devpath;
+
+        snprintf(buf, TASK_COMM_LEN, "blkback.%d.%s", blkif->domid, devname);
+        kfree(devpath);
+
+        return 0;
+}
+
+static void xen_update_blkif_status(struct xen_blkif *blkif)
+{
+        int err;
+        char name[TASK_COMM_LEN];
+
+        /* Not ready to connect? */
+        if (!blkif->irq || !blkif->vbd.bdev)
+                return;
+
+        /* Already connected? */
+        if (blkif->be->dev->state == XenbusStateConnected)
+                return;
+
+        /* Attempt to connect: exit if we fail to. */
+        connect(blkif->be);
+        if (blkif->be->dev->state != XenbusStateConnected)
+                return;
+
+        err = blkback_name(blkif, name);
+        if (err) {
+                xenbus_dev_error(blkif->be->dev, err, "get blkback dev name");
+                return;
+        }
+
+        err = filemap_write_and_wait(blkif->vbd.bdev->bd_inode->i_mapping);
+        if (err) {
+                xenbus_dev_error(blkif->be->dev, err, "block flush");
+                return;
+        }
+        invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);
+
+        blkif->xenblkd = kthread_run(xen_blkif_schedule, blkif, name);
+        if (IS_ERR(blkif->xenblkd)) {
+                err = PTR_ERR(blkif->xenblkd);
+                blkif->xenblkd = NULL;
+                xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
+        }
+}
+
+static struct xen_blkif *xen_blkif_alloc(domid_t domid)
+{
+        struct xen_blkif *blkif;
+
+        blkif = kmem_cache_alloc(xen_blkif_cachep, GFP_KERNEL);
+        if (!blkif)
+                return ERR_PTR(-ENOMEM);
+
+        memset(blkif, 0, sizeof(*blkif));
+        blkif->domid = domid;
+        spin_lock_init(&blkif->blk_ring_lock);
+        atomic_set(&blkif->refcnt, 1);
+        init_waitqueue_head(&blkif->wq);
+        blkif->st_print = jiffies;
+        init_waitqueue_head(&blkif->waiting_to_free);
+
+        return blkif;
+}
+
+static int map_frontend_page(struct xen_blkif *blkif, unsigned long shared_page)
+{
+        struct gnttab_map_grant_ref op;
+
+        gnttab_set_map_op(&op, (unsigned long)blkif->blk_ring_area->addr,
+                          GNTMAP_host_map, shared_page, blkif->domid);
+
+        if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
+                BUG();
+
+        if (op.status) {
+                DPRINTK("Grant table operation failure !\n");
+                return op.status;
+        }
+
+        blkif->shmem_ref = shared_page;
+        blkif->shmem_handle = op.handle;
+
+        return 0;
+}
+
+static void unmap_frontend_page(struct xen_blkif *blkif)
+{
+        struct gnttab_unmap_grant_ref op;
+
+        gnttab_set_unmap_op(&op, (unsigned long)blkif->blk_ring_area->addr,
+                            GNTMAP_host_map, blkif->shmem_handle);
+
+        if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
+                BUG();
+}
+
+static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
+                         unsigned int evtchn)
+{
+        int err;
+
+        /* Already connected through? */
+        if (blkif->irq)
+                return 0;
+
+        blkif->blk_ring_area = alloc_vm_area(PAGE_SIZE);
+        if (!blkif->blk_ring_area)
+                return -ENOMEM;
+
+        err = map_frontend_page(blkif, shared_page);
+        if (err) {
+                free_vm_area(blkif->blk_ring_area);
+                return err;
+        }
+
+        switch (blkif->blk_protocol) {
+        case BLKIF_PROTOCOL_NATIVE:
+        {
+                struct blkif_sring *sring;
+                sring = (struct blkif_sring *)blkif->blk_ring_area->addr;
+                BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
+                break;
+        }
+        case BLKIF_PROTOCOL_X86_32:
+        {
+                struct blkif_x86_32_sring *sring_x86_32;
+                sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring_area->addr;
+                BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
+                break;
+        }
+        case BLKIF_PROTOCOL_X86_64:
+        {
+                struct blkif_x86_64_sring *sring_x86_64;
+                sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring_area->addr;
+                BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
+                break;
+        }
+        default:
+                BUG();
+        }
+
+        err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
+                                                    xen_blkif_be_int, 0,
+                                                    "blkif-backend", blkif);
+        if (err < 0) {
+                unmap_frontend_page(blkif);
+                free_vm_area(blkif->blk_ring_area);
+                blkif->blk_rings.common.sring = NULL;
+                return err;
+        }
+        blkif->irq = err;
+
+        return 0;
+}
+
+static void xen_blkif_disconnect(struct xen_blkif *blkif)
+{
+        if (blkif->xenblkd) {
+                kthread_stop(blkif->xenblkd);
+                blkif->xenblkd = NULL;
+        }
+
+        atomic_dec(&blkif->refcnt);
+        wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
+        atomic_inc(&blkif->refcnt);
+
+        if (blkif->irq) {
+                unbind_from_irqhandler(blkif->irq, blkif);
+                blkif->irq = 0;
+        }
+
+        if (blkif->blk_rings.common.sring) {
+                unmap_frontend_page(blkif);
+                free_vm_area(blkif->blk_ring_area);
+                blkif->blk_rings.common.sring = NULL;
+        }
+}
+
+void xen_blkif_free(struct xen_blkif *blkif)
+{
+        if (!atomic_dec_and_test(&blkif->refcnt))
+                BUG();
+        kmem_cache_free(xen_blkif_cachep, blkif);
+}
+
+int __init xen_blkif_interface_init(void)
+{
+        xen_blkif_cachep = kmem_cache_create("blkif_cache",
+                                             sizeof(struct xen_blkif),
+                                             0, 0, NULL);
+        if (!xen_blkif_cachep)
+                return -ENOMEM;
+
+        return 0;
+}
+
+/*
+ *  sysfs interface for VBD I/O requests
+ */
+
+#define VBD_SHOW(name, format, args...)                                 \
+        static ssize_t show_##name(struct device *_dev,                 \
+                                   struct device_attribute *attr,       \
+                                   char *buf)                           \
+        {                                                               \
+                struct xenbus_device *dev = to_xenbus_device(_dev);     \
+                struct backend_info *be = dev_get_drvdata(&dev->dev);   \
+                                                                        \
+                return sprintf(buf, format, ##args);                    \
+        }                                                               \
+        static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
+
+VBD_SHOW(oo_req,  "%d\n", be->blkif->st_oo_req);
+VBD_SHOW(rd_req,  "%d\n", be->blkif->st_rd_req);
+VBD_SHOW(wr_req,  "%d\n", be->blkif->st_wr_req);
+VBD_SHOW(f_req,  "%d\n", be->blkif->st_f_req);
+VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
+VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
+
+static struct attribute *xen_vbdstat_attrs[] = {
+        &dev_attr_oo_req.attr,
+        &dev_attr_rd_req.attr,
+        &dev_attr_wr_req.attr,
+        &dev_attr_f_req.attr,
+        &dev_attr_rd_sect.attr,
+        &dev_attr_wr_sect.attr,
+        NULL
+};
+
+static struct attribute_group xen_vbdstat_group = {
+        .name = "statistics",
+        .attrs = xen_vbdstat_attrs,
+};
+
+VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
+VBD_SHOW(mode, "%s\n", be->mode);
+
+int xenvbd_sysfs_addif(struct xenbus_device *dev)
+{
+        int error;
+
+        error = device_create_file(&dev->dev, &dev_attr_physical_device);
+        if (error)
+                goto fail1;
+
+        error = device_create_file(&dev->dev, &dev_attr_mode);
+        if (error)
+                goto fail2;
+
+        error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
+        if (error)
+                goto fail3;
+
+        return 0;
+
+fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
+fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
+fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
+        return error;
+}
+
+void xenvbd_sysfs_delif(struct xenbus_device *dev)
+{
+        sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
+        device_remove_file(&dev->dev, &dev_attr_mode);
+        device_remove_file(&dev->dev, &dev_attr_physical_device);
+}
+
+
+static void xen_vbd_free(struct xen_vbd *vbd)
+{
+        if (vbd->bdev)
+                blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
+        vbd->bdev = NULL;
+}
+
+static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
+                          unsigned major, unsigned minor, int readonly,
+                          int cdrom)
+{
+        struct xen_vbd *vbd;
+        struct block_device *bdev;
+        struct request_queue *q;
+
+        vbd = &blkif->vbd;
+        vbd->handle   = handle;
+        vbd->readonly = readonly;
+        vbd->type     = 0;
+
+        vbd->pdevice  = MKDEV(major, minor);
+
+        bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
+                                 FMODE_READ : FMODE_WRITE, NULL);
+
+        if (IS_ERR(bdev)) {
+                DPRINTK("xen_vbd_create: device %08x could not be opened.\n",
+                        vbd->pdevice);
+                return -ENOENT;
+        }
+
+        vbd->bdev = bdev;
+        vbd->size = vbd_sz(vbd);
+
+        if (vbd->bdev->bd_disk == NULL) {
+                DPRINTK("xen_vbd_create: device %08x doesn't exist.\n",
+                        vbd->pdevice);
+                xen_vbd_free(vbd);
+                return -ENOENT;
+        }
+
+        if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
+                vbd->type |= VDISK_CDROM;
+        if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
+                vbd->type |= VDISK_REMOVABLE;
+
+        q = bdev_get_queue(bdev);
+        if (q && q->flush_flags)
+                vbd->flush_support = true;
+
+        DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
+                handle, blkif->domid);
+        return 0;
+}
+static int xen_blkbk_remove(struct xenbus_device *dev)
+{
+        struct backend_info *be = dev_get_drvdata(&dev->dev);
+
+        DPRINTK("");
+
+        if (be->major || be->minor)
+                xenvbd_sysfs_delif(dev);
+
+        if (be->backend_watch.node) {
+                unregister_xenbus_watch(&be->backend_watch);
+                kfree(be->backend_watch.node);
+                be->backend_watch.node = NULL;
+        }
+
+        if (be->blkif) {
+                xen_blkif_disconnect(be->blkif);
+                xen_vbd_free(&be->blkif->vbd);
+                xen_blkif_free(be->blkif);
+                be->blkif = NULL;
+        }
+
+        kfree(be);
+        dev_set_drvdata(&dev->dev, NULL);
+        return 0;
+}
+
+int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
+                              struct backend_info *be, int state)
+{
+        struct xenbus_device *dev = be->dev;
+        int err;
+
+        err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
+                            "%d", state);
+        if (err)
+                xenbus_dev_fatal(dev, err, "writing feature-flush-cache");
+
+        return err;
+}
+
+/*
+ * Entry point to this code when a new device is created.  Allocate the basic
+ * structures, and watch the store waiting for the hotplug scripts to tell us
+ * the device's physical major and minor numbers.  Switch to InitWait.
+ */
+static int xen_blkbk_probe(struct xenbus_device *dev,
+                           const struct xenbus_device_id *id)
+{
+        int err;
+        struct backend_info *be = kzalloc(sizeof(struct backend_info),
+                                          GFP_KERNEL);
+        if (!be) {
+                xenbus_dev_fatal(dev, -ENOMEM,
+                                 "allocating backend structure");
+                return -ENOMEM;
+        }
+        be->dev = dev;
+        dev_set_drvdata(&dev->dev, be);
+
+        be->blkif = xen_blkif_alloc(dev->otherend_id);
+        if (IS_ERR(be->blkif)) {
+                err = PTR_ERR(be->blkif);
+                be->blkif = NULL;
+                xenbus_dev_fatal(dev, err, "creating block interface");
+                goto fail;
+        }
+
+        /* setup back pointer */
+        be->blkif->be = be;
+
+        err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
+                                   "%s/%s", dev->nodename, "physical-device");
+        if (err)
+                goto fail;
+
+        err = xenbus_switch_state(dev, XenbusStateInitWait);
+        if (err)
+                goto fail;
+
+        return 0;
+
+fail:
+        DPRINTK("failed");
+        xen_blkbk_remove(dev);
+        return err;
+}
+
+
+/*
+ * Callback received when the hotplug scripts have placed the physical-device
+ * node.  Read it and the mode node, and create a vbd.  If the frontend is
+ * ready, connect.
+ */
+static void backend_changed(struct xenbus_watch *watch,
+                            const char **vec, unsigned int len)
+{
+        int err;
+        unsigned major;
+        unsigned minor;
+        struct backend_info *be
+                = container_of(watch, struct backend_info, backend_watch);
+        struct xenbus_device *dev = be->dev;
+        int cdrom = 0;
+        char *device_type;
+
+        DPRINTK("");
+
+        err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
+                           &major, &minor);
+        if (XENBUS_EXIST_ERR(err)) {
+                /*
+                 * Since this watch will fire once immediately after it is
+                 * registered, we expect this.  Ignore it, and wait for the
+                 * hotplug scripts.
+                 */
+                return;
+        }
+        if (err != 2) {
+                xenbus_dev_fatal(dev, err, "reading physical-device");
+                return;
+        }
+
+        if ((be->major || be->minor) &&
+            ((be->major != major) || (be->minor != minor))) {
+                pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
+                        be->major, be->minor, major, minor);
+                return;
+        }
+
+        be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
+        if (IS_ERR(be->mode)) {
+                err = PTR_ERR(be->mode);
+                be->mode = NULL;
+                xenbus_dev_fatal(dev, err, "reading mode");
+                return;
+        }
+
+        device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
+        if (!IS_ERR(device_type)) {
+                cdrom = strcmp(device_type, "cdrom") == 0;
+                kfree(device_type);
+        }
+
+        if (be->major == 0 && be->minor == 0) {
+                /* Front end dir is a number, which is used as the handle. */
+
+                char *p = strrchr(dev->otherend, '/') + 1;
+                long handle;
+                err = strict_strtoul(p, 0, &handle);
+                if (err)
+                        return;
+
+                be->major = major;
+                be->minor = minor;
+
+                err = xen_vbd_create(be->blkif, handle, major, minor,
+                                 (NULL == strchr(be->mode, 'w')), cdrom);
+                if (err) {
+                        be->major = 0;
+                        be->minor = 0;
+                        xenbus_dev_fatal(dev, err, "creating vbd structure");
+                        return;
+                }
+
+                err = xenvbd_sysfs_addif(dev);
+                if (err) {
+                        xen_vbd_free(&be->blkif->vbd);
+                        be->major = 0;
+                        be->minor = 0;
+                        xenbus_dev_fatal(dev, err, "creating sysfs entries");
+                        return;
+                }
+
+                /* We're potentially connected now */
+                xen_update_blkif_status(be->blkif);
+        }
+}
+
+
+/*
+ * Callback received when the frontend's state changes.
+ */
+static void frontend_changed(struct xenbus_device *dev,
+                             enum xenbus_state frontend_state)
+{
+        struct backend_info *be = dev_get_drvdata(&dev->dev);
+        int err;
+
+        DPRINTK("%s", xenbus_strstate(frontend_state));
+
+        switch (frontend_state) {
+        case XenbusStateInitialising:
+                if (dev->state == XenbusStateClosed) {
+                        pr_info(DRV_PFX "%s: prepare for reconnect\n",
+                                dev->nodename);
+                        xenbus_switch_state(dev, XenbusStateInitWait);
+                }
+                break;
+
+        case XenbusStateInitialised:
+        case XenbusStateConnected:
+                /*
+                 * Ensure we connect even when two watches fire in
+                 * close successsion and we miss the intermediate value
+                 * of frontend_state.
+                 */
+                if (dev->state == XenbusStateConnected)
+                        break;
+
+                /*
+                 * Enforce precondition before potential leak point.
+                 * blkif_disconnect() is idempotent.
+                 */
+                xen_blkif_disconnect(be->blkif);
+
+                err = connect_ring(be);
+                if (err)
+                        break;
+                xen_update_blkif_status(be->blkif);
+                break;
+
+        case XenbusStateClosing:
+                xen_blkif_disconnect(be->blkif);
+                xenbus_switch_state(dev, XenbusStateClosing);
+                break;
+
+        case XenbusStateClosed:
+                xenbus_switch_state(dev, XenbusStateClosed);
+                if (xenbus_dev_is_online(dev))
+                        break;
+                /* fall through if not online */
+        case XenbusStateUnknown:
+                /* implies blkif_disconnect() via blkback_remove() */
+                device_unregister(&dev->dev);
+                break;
+
+        default:
+                xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
+                                 frontend_state);
+                break;
+        }
+}
+
+
+/* ** Connection ** */
+
+
+/*
+ * Write the physical details regarding the block device to the store, and
+ * switch to Connected state.
+ */
+static void connect(struct backend_info *be)
+{
+        struct xenbus_transaction xbt;
+        int err;
+        struct xenbus_device *dev = be->dev;
+
+        DPRINTK("%s", dev->otherend);
+
+        /* Supply the information about the device the frontend needs */
+again:
+        err = xenbus_transaction_start(&xbt);
+        if (err) {
+                xenbus_dev_fatal(dev, err, "starting transaction");
+                return;
+        }
+
+        err = xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
+        if (err)
+                goto abort;
+
+        err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
+                            (unsigned long long)vbd_sz(&be->blkif->vbd));
+        if (err) {
+                xenbus_dev_fatal(dev, err, "writing %s/sectors",
+                                 dev->nodename);
+                goto abort;
+        }
+
+        /* FIXME: use a typename instead */
+        err = xenbus_printf(xbt, dev->nodename, "info", "%u",
+                            be->blkif->vbd.type |
+                            (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
+        if (err) {
+                xenbus_dev_fatal(dev, err, "writing %s/info",
+                                 dev->nodename);
+                goto abort;
+        }
+        err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
+                            (unsigned long)
+                            bdev_logical_block_size(be->blkif->vbd.bdev));
+        if (err) {
+                xenbus_dev_fatal(dev, err, "writing %s/sector-size",
+                                 dev->nodename);
+                goto abort;
+        }
+
+        err = xenbus_transaction_end(xbt, 0);
+        if (err == -EAGAIN)
+                goto again;
+        if (err)
+                xenbus_dev_fatal(dev, err, "ending transaction");
+
+        err = xenbus_switch_state(dev, XenbusStateConnected);
+        if (err)
+                xenbus_dev_fatal(dev, err, "switching to Connected state",
+                                 dev->nodename);
+
+        return;
+ abort:
+        xenbus_transaction_end(xbt, 1);
+}
+
+
+static int connect_ring(struct backend_info *be)
+{
+        struct xenbus_device *dev = be->dev;
+        unsigned long ring_ref;
+        unsigned int evtchn;
+        char protocol[64] = "";
+        int err;
+
+        DPRINTK("%s", dev->otherend);
+
+        err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
+                            &ring_ref, "event-channel", "%u", &evtchn, NULL);
+        if (err) {
+                xenbus_dev_fatal(dev, err,
+                                 "reading %s/ring-ref and event-channel",
+                                 dev->otherend);
+                return err;
+        }
+
+        be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
+        err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
+                            "%63s", protocol, NULL);
+        if (err)
+                strcpy(protocol, "unspecified, assuming native");
+        else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
+                be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
+        else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
+                be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
+        else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
+                be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
+        else {
+                xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
+                return -1;
+        }
+        pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s)\n",
+                ring_ref, evtchn, be->blkif->blk_protocol, protocol);
+
+        /* Map the shared frame, irq etc. */
+        err = xen_blkif_map(be->blkif, ring_ref, evtchn);
+        if (err) {
+                xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
+                                 ring_ref, evtchn);
+                return err;
+        }
+
+        return 0;
+}
+
+
+/* ** Driver Registration ** */
+
+
+static const struct xenbus_device_id xen_blkbk_ids[] = {
+        { "vbd" },
+        { "" }
+};
+
+
+static struct xenbus_driver xen_blkbk = {
+        .name = "vbd",
+        .owner = THIS_MODULE,
+        .ids = xen_blkbk_ids,
+        .probe = xen_blkbk_probe,
+        .remove = xen_blkbk_remove,
+        .otherend_changed = frontend_changed
+};
+
+
+int xen_blkif_xenbus_init(void)
+{
+        return xenbus_register_backend(&xen_blkbk);
+}