/******************************************************************************
   * gntdev.c
   *
   * Device for accessing (in user-space) pages that have been granted by other
   * domains.
   *
   * Copyright (c) 2006-2007, D G Murray.
   *           (c) 2009 Gerd Hoffmann <kraxel@redhat.com>
   *
   * 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.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #undef DEBUG
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/miscdevice.h>
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/mman.h>
  #include <linux/mmu_notifier.h>
  #include <linux/types.h>
  #include <linux/uaccess.h>
  #include <linux/sched.h>
  #include <linux/spinlock.h>
  #include <linux/slab.h>

  #include <linux/highmem.h>

  
  #include <xen/xen.h>
  #include <xen/grant_table.h>

  #include <xen/balloon.h>

  #include <xen/gntdev.h>

  #include <xen/events.h>

  #include <asm/xen/hypervisor.h>
  #include <asm/xen/hypercall.h>
  #include <asm/xen/page.h>
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Derek G. Murray <Derek.Murray@cl.cam.ac.uk>, "
  	      "Gerd Hoffmann <kraxel@redhat.com>");
  MODULE_DESCRIPTION("User-space granted page access driver");

  static int limit = 1024*1024;

  module_param(limit, int, 0644);

  MODULE_PARM_DESC(limit, "Maximum number of grants that may be mapped by "
  		"the gntdev device");
  
  static atomic_t pages_mapped = ATOMIC_INIT(0);

  static int use_ptemod;

  struct gntdev_priv {
  	struct list_head maps;

  	/* lock protects maps from concurrent changes */
  	spinlock_t lock;
  	struct mm_struct *mm;
  	struct mmu_notifier mn;
  };

  struct unmap_notify {
  	int flags;
  	/* Address relative to the start of the grant_map */
  	int addr;
  	int event;
  };

  struct grant_map {
  	struct list_head next;

  	struct vm_area_struct *vma;
  	int index;
  	int count;
  	int flags;

  	atomic_t users;

  	struct unmap_notify notify;

  	struct ioctl_gntdev_grant_ref *grants;
  	struct gnttab_map_grant_ref   *map_ops;
  	struct gnttab_unmap_grant_ref *unmap_ops;

  	struct gnttab_map_grant_ref   *kmap_ops;

  	struct page **pages;

  };

  static int unmap_grant_pages(struct grant_map *map, int offset, int pages);

  /* ------------------------------------------------------------------ */
  
  static void gntdev_print_maps(struct gntdev_priv *priv,
  			      char *text, int text_index)
  {
  #ifdef DEBUG
  	struct grant_map *map;

  	pr_debug("%s: maps list (priv %p)
  ", __func__, priv);

  	list_for_each_entry(map, &priv->maps, next)
  		pr_debug("  index %2d, count %2d %s
  ",
  		       map->index, map->count,
  		       map->index == text_index && text ? text : "");
  #endif
  }
  
  static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
  {
  	struct grant_map *add;

  	int i;

  
  	add = kzalloc(sizeof(struct grant_map), GFP_KERNEL);
  	if (NULL == add)
  		return NULL;

  	add->grants    = kcalloc(count, sizeof(add->grants[0]), GFP_KERNEL);
  	add->map_ops   = kcalloc(count, sizeof(add->map_ops[0]), GFP_KERNEL);
  	add->unmap_ops = kcalloc(count, sizeof(add->unmap_ops[0]), GFP_KERNEL);
  	add->kmap_ops  = kcalloc(count, sizeof(add->kmap_ops[0]), GFP_KERNEL);
  	add->pages     = kcalloc(count, sizeof(add->pages[0]), GFP_KERNEL);

  	if (NULL == add->grants    ||
  	    NULL == add->map_ops   ||
  	    NULL == add->unmap_ops ||

  	    NULL == add->kmap_ops  ||

  	    NULL == add->pages)

  		goto err;

  	if (alloc_xenballooned_pages(count, add->pages, false /* lowmem */))

  		goto err;

  	for (i = 0; i < count; i++) {

  		add->map_ops[i].handle = -1;
  		add->unmap_ops[i].handle = -1;

  		add->kmap_ops[i].handle = -1;

  	}

  	add->index = 0;
  	add->count = count;

  	atomic_set(&add->users, 1);

  	return add;
  
  err:

  	kfree(add->pages);

  	kfree(add->grants);
  	kfree(add->map_ops);
  	kfree(add->unmap_ops);

  	kfree(add->kmap_ops);

  	kfree(add);
  	return NULL;
  }
  
  static void gntdev_add_map(struct gntdev_priv *priv, struct grant_map *add)
  {
  	struct grant_map *map;
  
  	list_for_each_entry(map, &priv->maps, next) {
  		if (add->index + add->count < map->index) {
  			list_add_tail(&add->next, &map->next);
  			goto done;
  		}
  		add->index = map->index + map->count;
  	}
  	list_add_tail(&add->next, &priv->maps);
  
  done:

  	gntdev_print_maps(priv, "[new]", add->index);
  }
  
  static struct grant_map *gntdev_find_map_index(struct gntdev_priv *priv,
  		int index, int count)
  {
  	struct grant_map *map;
  
  	list_for_each_entry(map, &priv->maps, next) {
  		if (map->index != index)
  			continue;

  		if (count && map->count != count)

  			continue;
  		return map;
  	}
  	return NULL;
  }

  static void gntdev_put_map(struct grant_map *map)

  {
  	if (!map)
  		return;

  	if (!atomic_dec_and_test(&map->users))
  		return;
  
  	atomic_sub(map->count, &pages_mapped);

  	if (map->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {

  		notify_remote_via_evtchn(map->notify.event);

  		evtchn_put(map->notify.event);
  	}

  	if (map->pages) {
  		if (!use_ptemod)
  			unmap_grant_pages(map, 0, map->count);

  		free_xenballooned_pages(map->count, map->pages);

  	}

  	kfree(map->pages);

  	kfree(map->grants);
  	kfree(map->map_ops);
  	kfree(map->unmap_ops);
  	kfree(map);
  }
  
  /* ------------------------------------------------------------------ */
  
  static int find_grant_ptes(pte_t *pte, pgtable_t token,
  		unsigned long addr, void *data)
  {
  	struct grant_map *map = data;
  	unsigned int pgnr = (addr - map->vma->vm_start) >> PAGE_SHIFT;

  	int flags = map->flags | GNTMAP_application_map | GNTMAP_contains_pte;

  	u64 pte_maddr;
  
  	BUG_ON(pgnr >= map->count);

  	pte_maddr = arbitrary_virt_to_machine(pte).maddr;

  	gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, flags,

  			  map->grants[pgnr].ref,
  			  map->grants[pgnr].domid);

  	gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr, flags,

  			    -1 /* handle */);

  	return 0;
  }
  
  static int map_grant_pages(struct grant_map *map)
  {
  	int i, err = 0;

  
  	if (!use_ptemod) {

  		/* Note: it could already be mapped */

  		if (map->map_ops[0].handle != -1)

  			return 0;

  		for (i = 0; i < map->count; i++) {

  			unsigned long addr = (unsigned long)

  				pfn_to_kaddr(page_to_pfn(map->pages[i]));
  			gnttab_set_map_op(&map->map_ops[i], addr, map->flags,
  				map->grants[i].ref,
  				map->grants[i].domid);
  			gnttab_set_unmap_op(&map->unmap_ops[i], addr,

  				map->flags, -1 /* handle */);

  		}

  	} else {
  		/*
  		 * Setup the map_ops corresponding to the pte entries pointing
  		 * to the kernel linear addresses of the struct pages.
  		 * These ptes are completely different from the user ptes dealt
  		 * with find_grant_ptes.
  		 */
  		for (i = 0; i < map->count; i++) {
  			unsigned level;
  			unsigned long address = (unsigned long)
  				pfn_to_kaddr(page_to_pfn(map->pages[i]));
  			pte_t *ptep;
  			u64 pte_maddr = 0;
  			BUG_ON(PageHighMem(map->pages[i]));
  
  			ptep = lookup_address(address, &level);
  			pte_maddr = arbitrary_virt_to_machine(ptep).maddr;
  			gnttab_set_map_op(&map->kmap_ops[i], pte_maddr,
  				map->flags |
  				GNTMAP_host_map |
  				GNTMAP_contains_pte,
  				map->grants[i].ref,
  				map->grants[i].domid);
  		}

  	}

  
  	pr_debug("map %d+%d
  ", map->index, map->count);

  	err = gnttab_map_refs(map->map_ops, use_ptemod ? map->kmap_ops : NULL,
  			map->pages, map->count);

  	if (err)
  		return err;
  
  	for (i = 0; i < map->count; i++) {
  		if (map->map_ops[i].status)
  			err = -EINVAL;

  		else {
  			BUG_ON(map->map_ops[i].handle == -1);
  			map->unmap_ops[i].handle = map->map_ops[i].handle;
  			pr_debug("map handle=%d
  ", map->map_ops[i].handle);
  		}

  	}
  	return err;
  }

  static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)

  {
  	int i, err = 0;

  	if (map->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
  		int pgno = (map->notify.addr >> PAGE_SHIFT);

  		if (pgno >= offset && pgno < offset + pages && use_ptemod) {

  			void __user *tmp = (void __user *)
  				map->vma->vm_start + map->notify.addr;

  			err = copy_to_user(tmp, &err, 1);
  			if (err)

  				return -EFAULT;

  			map->notify.flags &= ~UNMAP_NOTIFY_CLEAR_BYTE;
  		} else if (pgno >= offset && pgno < offset + pages) {

  			uint8_t *tmp = kmap(map->pages[pgno]);
  			tmp[map->notify.addr & (PAGE_SIZE-1)] = 0;
  			kunmap(map->pages[pgno]);
  			map->notify.flags &= ~UNMAP_NOTIFY_CLEAR_BYTE;
  		}
  	}

  	err = gnttab_unmap_refs(map->unmap_ops + offset, map->pages + offset,
  				pages, true);

  	if (err)
  		return err;
  
  	for (i = 0; i < pages; i++) {
  		if (map->unmap_ops[offset+i].status)
  			err = -EINVAL;

  		pr_debug("unmap handle=%d st=%d
  ",
  			map->unmap_ops[offset+i].handle,
  			map->unmap_ops[offset+i].status);
  		map->unmap_ops[offset+i].handle = -1;

  	}
  	return err;
  }

  static int unmap_grant_pages(struct grant_map *map, int offset, int pages)
  {
  	int range, err = 0;
  
  	pr_debug("unmap %d+%d [%d+%d]
  ", map->index, map->count, offset, pages);
  
  	/* It is possible the requested range will have a "hole" where we
  	 * already unmapped some of the grants. Only unmap valid ranges.
  	 */
  	while (pages && !err) {

  		while (pages && map->unmap_ops[offset].handle == -1) {

  			offset++;
  			pages--;
  		}
  		range = 0;
  		while (range < pages) {

  			if (map->unmap_ops[offset+range].handle == -1) {

  				range--;
  				break;
  			}
  			range++;
  		}
  		err = __unmap_grant_pages(map, offset, range);
  		offset += range;
  		pages -= range;
  	}
  
  	return err;
  }

  /* ------------------------------------------------------------------ */

  static void gntdev_vma_open(struct vm_area_struct *vma)
  {
  	struct grant_map *map = vma->vm_private_data;
  
  	pr_debug("gntdev_vma_open %p
  ", vma);
  	atomic_inc(&map->users);
  }

  static void gntdev_vma_close(struct vm_area_struct *vma)
  {
  	struct grant_map *map = vma->vm_private_data;

  	pr_debug("gntdev_vma_close %p
  ", vma);

  	map->vma = NULL;
  	vma->vm_private_data = NULL;

  	gntdev_put_map(map);

  }

  static struct vm_operations_struct gntdev_vmops = {

  	.open = gntdev_vma_open,

  	.close = gntdev_vma_close,

  };
  
  /* ------------------------------------------------------------------ */
  
  static void mn_invl_range_start(struct mmu_notifier *mn,
  				struct mm_struct *mm,
  				unsigned long start, unsigned long end)
  {
  	struct gntdev_priv *priv = container_of(mn, struct gntdev_priv, mn);
  	struct grant_map *map;
  	unsigned long mstart, mend;
  	int err;
  
  	spin_lock(&priv->lock);
  	list_for_each_entry(map, &priv->maps, next) {
  		if (!map->vma)
  			continue;

  		if (map->vma->vm_start >= end)
  			continue;
  		if (map->vma->vm_end <= start)
  			continue;
  		mstart = max(start, map->vma->vm_start);
  		mend   = min(end,   map->vma->vm_end);
  		pr_debug("map %d+%d (%lx %lx), range %lx %lx, mrange %lx %lx
  ",
  				map->index, map->count,
  				map->vma->vm_start, map->vma->vm_end,
  				start, end, mstart, mend);
  		err = unmap_grant_pages(map,
  					(mstart - map->vma->vm_start) >> PAGE_SHIFT,
  					(mend - mstart) >> PAGE_SHIFT);
  		WARN_ON(err);
  	}
  	spin_unlock(&priv->lock);
  }
  
  static void mn_invl_page(struct mmu_notifier *mn,
  			 struct mm_struct *mm,
  			 unsigned long address)
  {
  	mn_invl_range_start(mn, mm, address, address + PAGE_SIZE);
  }
  
  static void mn_release(struct mmu_notifier *mn,
  		       struct mm_struct *mm)
  {
  	struct gntdev_priv *priv = container_of(mn, struct gntdev_priv, mn);
  	struct grant_map *map;
  	int err;
  
  	spin_lock(&priv->lock);
  	list_for_each_entry(map, &priv->maps, next) {
  		if (!map->vma)
  			continue;
  		pr_debug("map %d+%d (%lx %lx)
  ",
  				map->index, map->count,
  				map->vma->vm_start, map->vma->vm_end);
  		err = unmap_grant_pages(map, /* offset */ 0, map->count);
  		WARN_ON(err);
  	}
  	spin_unlock(&priv->lock);
  }
  
  struct mmu_notifier_ops gntdev_mmu_ops = {
  	.release                = mn_release,
  	.invalidate_page        = mn_invl_page,
  	.invalidate_range_start = mn_invl_range_start,
  };
  
  /* ------------------------------------------------------------------ */
  
  static int gntdev_open(struct inode *inode, struct file *flip)
  {
  	struct gntdev_priv *priv;
  	int ret = 0;
  
  	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
  	if (!priv)
  		return -ENOMEM;
  
  	INIT_LIST_HEAD(&priv->maps);
  	spin_lock_init(&priv->lock);

  	if (use_ptemod) {
  		priv->mm = get_task_mm(current);
  		if (!priv->mm) {
  			kfree(priv);
  			return -ENOMEM;
  		}
  		priv->mn.ops = &gntdev_mmu_ops;
  		ret = mmu_notifier_register(&priv->mn, priv->mm);
  		mmput(priv->mm);

  	}

  
  	if (ret) {
  		kfree(priv);
  		return ret;
  	}
  
  	flip->private_data = priv;
  	pr_debug("priv %p
  ", priv);
  
  	return 0;
  }
  
  static int gntdev_release(struct inode *inode, struct file *flip)
  {
  	struct gntdev_priv *priv = flip->private_data;
  	struct grant_map *map;

  
  	pr_debug("priv %p
  ", priv);

  	while (!list_empty(&priv->maps)) {
  		map = list_entry(priv->maps.next, struct grant_map, next);

  		list_del(&map->next);
  		gntdev_put_map(map);

  	}

  	if (use_ptemod)
  		mmu_notifier_unregister(&priv->mn, priv->mm);

  	kfree(priv);
  	return 0;
  }
  
  static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv,
  				       struct ioctl_gntdev_map_grant_ref __user *u)
  {
  	struct ioctl_gntdev_map_grant_ref op;
  	struct grant_map *map;
  	int err;
  
  	if (copy_from_user(&op, u, sizeof(op)) != 0)
  		return -EFAULT;
  	pr_debug("priv %p, add %d
  ", priv, op.count);
  	if (unlikely(op.count <= 0))
  		return -EINVAL;

  
  	err = -ENOMEM;
  	map = gntdev_alloc_map(priv, op.count);
  	if (!map)
  		return err;

  	if (unlikely(atomic_add_return(op.count, &pages_mapped) > limit)) {
  		pr_debug("can't map: over limit
  ");
  		gntdev_put_map(map);

  		return err;
  	}

  	if (copy_from_user(map->grants, &u->refs,
  			   sizeof(map->grants[0]) * op.count) != 0) {
  		gntdev_put_map(map);

  		return err;
  	}

  	spin_lock(&priv->lock);
  	gntdev_add_map(priv, map);
  	op.index = map->index << PAGE_SHIFT;
  	spin_unlock(&priv->lock);

  	if (copy_to_user(u, &op, sizeof(op)) != 0)
  		return -EFAULT;

  	return 0;
  }
  
  static long gntdev_ioctl_unmap_grant_ref(struct gntdev_priv *priv,
  					 struct ioctl_gntdev_unmap_grant_ref __user *u)
  {
  	struct ioctl_gntdev_unmap_grant_ref op;
  	struct grant_map *map;
  	int err = -ENOENT;
  
  	if (copy_from_user(&op, u, sizeof(op)) != 0)
  		return -EFAULT;
  	pr_debug("priv %p, del %d+%d
  ", priv, (int)op.index, (int)op.count);
  
  	spin_lock(&priv->lock);
  	map = gntdev_find_map_index(priv, op.index >> PAGE_SHIFT, op.count);

  	if (map) {
  		list_del(&map->next);

  		err = 0;
  	}

  	spin_unlock(&priv->lock);

  	if (map)
  		gntdev_put_map(map);

  	return err;
  }
  
  static long gntdev_ioctl_get_offset_for_vaddr(struct gntdev_priv *priv,
  					      struct ioctl_gntdev_get_offset_for_vaddr __user *u)
  {
  	struct ioctl_gntdev_get_offset_for_vaddr op;

  	struct vm_area_struct *vma;

  	struct grant_map *map;
  
  	if (copy_from_user(&op, u, sizeof(op)) != 0)
  		return -EFAULT;
  	pr_debug("priv %p, offset for vaddr %lx
  ", priv, (unsigned long)op.vaddr);

  	vma = find_vma(current->mm, op.vaddr);
  	if (!vma || vma->vm_ops != &gntdev_vmops)

  		return -EINVAL;

  
  	map = vma->vm_private_data;
  	if (!map)
  		return -EINVAL;

  	op.offset = map->index << PAGE_SHIFT;
  	op.count = map->count;

  
  	if (copy_to_user(u, &op, sizeof(op)) != 0)
  		return -EFAULT;
  	return 0;
  }

  static long gntdev_ioctl_notify(struct gntdev_priv *priv, void __user *u)
  {
  	struct ioctl_gntdev_unmap_notify op;
  	struct grant_map *map;
  	int rc;

  	int out_flags;
  	unsigned int out_event;

  
  	if (copy_from_user(&op, u, sizeof(op)))
  		return -EFAULT;
  
  	if (op.action & ~(UNMAP_NOTIFY_CLEAR_BYTE|UNMAP_NOTIFY_SEND_EVENT))
  		return -EINVAL;

  	/* We need to grab a reference to the event channel we are going to use
  	 * to send the notify before releasing the reference we may already have
  	 * (if someone has called this ioctl twice). This is required so that
  	 * it is possible to change the clear_byte part of the notification
  	 * without disturbing the event channel part, which may now be the last
  	 * reference to that event channel.
  	 */
  	if (op.action & UNMAP_NOTIFY_SEND_EVENT) {
  		if (evtchn_get(op.event_channel_port))
  			return -EINVAL;
  	}
  
  	out_flags = op.action;
  	out_event = op.event_channel_port;

  	spin_lock(&priv->lock);
  
  	list_for_each_entry(map, &priv->maps, next) {
  		uint64_t begin = map->index << PAGE_SHIFT;
  		uint64_t end = (map->index + map->count) << PAGE_SHIFT;
  		if (op.index >= begin && op.index < end)
  			goto found;
  	}
  	rc = -ENOENT;
  	goto unlock_out;
  
   found:

  	if ((op.action & UNMAP_NOTIFY_CLEAR_BYTE) &&
  			(map->flags & GNTMAP_readonly)) {
  		rc = -EINVAL;
  		goto unlock_out;
  	}

  	out_flags = map->notify.flags;
  	out_event = map->notify.event;

  	map->notify.flags = op.action;
  	map->notify.addr = op.index - (map->index << PAGE_SHIFT);
  	map->notify.event = op.event_channel_port;

  	rc = 0;

   unlock_out:
  	spin_unlock(&priv->lock);

  
  	/* Drop the reference to the event channel we did not save in the map */
  	if (out_flags & UNMAP_NOTIFY_SEND_EVENT)
  		evtchn_put(out_event);

  	return rc;
  }

  static long gntdev_ioctl(struct file *flip,
  			 unsigned int cmd, unsigned long arg)
  {
  	struct gntdev_priv *priv = flip->private_data;
  	void __user *ptr = (void __user *)arg;
  
  	switch (cmd) {
  	case IOCTL_GNTDEV_MAP_GRANT_REF:
  		return gntdev_ioctl_map_grant_ref(priv, ptr);
  
  	case IOCTL_GNTDEV_UNMAP_GRANT_REF:
  		return gntdev_ioctl_unmap_grant_ref(priv, ptr);
  
  	case IOCTL_GNTDEV_GET_OFFSET_FOR_VADDR:
  		return gntdev_ioctl_get_offset_for_vaddr(priv, ptr);

  	case IOCTL_GNTDEV_SET_UNMAP_NOTIFY:
  		return gntdev_ioctl_notify(priv, ptr);

  	default:
  		pr_debug("priv %p, unknown cmd %x
  ", priv, cmd);
  		return -ENOIOCTLCMD;
  	}
  
  	return 0;
  }
  
  static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
  {
  	struct gntdev_priv *priv = flip->private_data;
  	int index = vma->vm_pgoff;
  	int count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
  	struct grant_map *map;

  	int i, err = -EINVAL;

  
  	if ((vma->vm_flags & VM_WRITE) && !(vma->vm_flags & VM_SHARED))
  		return -EINVAL;
  
  	pr_debug("map %d+%d at %lx (pgoff %lx)
  ",
  			index, count, vma->vm_start, vma->vm_pgoff);
  
  	spin_lock(&priv->lock);
  	map = gntdev_find_map_index(priv, index, count);
  	if (!map)
  		goto unlock_out;

  	if (use_ptemod && map->vma)

  		goto unlock_out;

  	if (use_ptemod && priv->mm != vma->vm_mm) {

  		printk(KERN_WARNING "Huh? Other mm?
  ");
  		goto unlock_out;
  	}

  	atomic_inc(&map->users);

  	vma->vm_ops = &gntdev_vmops;

  	vma->vm_flags |= VM_RESERVED|VM_DONTEXPAND;
  
  	if (use_ptemod)
  		vma->vm_flags |= VM_DONTCOPY|VM_PFNMAP;

  
  	vma->vm_private_data = map;

  	if (use_ptemod)
  		map->vma = vma;

  	if (map->flags) {
  		if ((vma->vm_flags & VM_WRITE) &&
  				(map->flags & GNTMAP_readonly))

  			goto out_unlock_put;

  	} else {
  		map->flags = GNTMAP_host_map;
  		if (!(vma->vm_flags & VM_WRITE))
  			map->flags |= GNTMAP_readonly;
  	}

  	spin_unlock(&priv->lock);

  	if (use_ptemod) {
  		err = apply_to_page_range(vma->vm_mm, vma->vm_start,
  					  vma->vm_end - vma->vm_start,
  					  find_grant_ptes, map);
  		if (err) {
  			printk(KERN_WARNING "find_grant_ptes() failure.
  ");

  			goto out_put_map;

  		}

  	}
  
  	err = map_grant_pages(map);

  	if (err)
  		goto out_put_map;

  	if (!use_ptemod) {
  		for (i = 0; i < count; i++) {
  			err = vm_insert_page(vma, vma->vm_start + i*PAGE_SIZE,
  				map->pages[i]);
  			if (err)

  				goto out_put_map;

  		}
  	}

  	return 0;

  unlock_out:
  	spin_unlock(&priv->lock);
  	return err;

  out_unlock_put:
  	spin_unlock(&priv->lock);

  out_put_map:

  	if (use_ptemod)
  		map->vma = NULL;

  	gntdev_put_map(map);
  	return err;

  }
  
  static const struct file_operations gntdev_fops = {
  	.owner = THIS_MODULE,
  	.open = gntdev_open,
  	.release = gntdev_release,
  	.mmap = gntdev_mmap,
  	.unlocked_ioctl = gntdev_ioctl
  };
  
  static struct miscdevice gntdev_miscdev = {
  	.minor        = MISC_DYNAMIC_MINOR,
  	.name         = "xen/gntdev",
  	.fops         = &gntdev_fops,
  };
  
  /* ------------------------------------------------------------------ */
  
  static int __init gntdev_init(void)
  {
  	int err;
  
  	if (!xen_domain())
  		return -ENODEV;

  	use_ptemod = xen_pv_domain();

  	err = misc_register(&gntdev_miscdev);
  	if (err != 0) {
  		printk(KERN_ERR "Could not register gntdev device
  ");
  		return err;
  	}
  	return 0;
  }
  
  static void __exit gntdev_exit(void)
  {
  	misc_deregister(&gntdev_miscdev);
  }
  
  module_init(gntdev_init);
  module_exit(gntdev_exit);
  
  /* ------------------------------------------------------------------ */