Initial import

1 files changed, 924 insertions, 0 deletions

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
new file mode 100644
index 000000000..892748507
--- /dev/null
+++ b/drivers/xen/gntdev.c
@@ -0,0 +1,924 @@
+/******************************************************************************
+ * 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
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#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;
+#define populate_freeable_maps use_ptemod
+
+struct gntdev_priv {
+	/* maps with visible offsets in the file descriptor */
+	struct list_head maps;
+	/* maps that are not visible; will be freed on munmap.
+	 * Only populated if populate_freeable_maps == 1 */
+	struct list_head freeable_maps;
+	/* lock protects maps and freeable_maps */
+	struct mutex 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 gnttab_unmap_grant_ref *kunmap_ops;
+	struct page **pages;
+	unsigned long pages_vm_start;
+};
+
+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)\n", __func__, priv);
+	list_for_each_entry(map, &priv->maps, next)
+		pr_debug("  index %2d, count %2d %s\n",
+		       map->index, map->count,
+		       map->index == text_index && text ? text : "");
+#endif
+}
+
+static void gntdev_free_map(struct grant_map *map)
+{
+	if (map == NULL)
+		return;
+
+	if (map->pages)
+		gnttab_free_pages(map->count, map->pages);
+	kfree(map->pages);
+	kfree(map->grants);
+	kfree(map->map_ops);
+	kfree(map->unmap_ops);
+	kfree(map->kmap_ops);
+	kfree(map->kunmap_ops);
+	kfree(map);
+}
+
+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->kunmap_ops = kcalloc(count, sizeof(add->kunmap_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->kunmap_ops ||
+	    NULL == add->pages)
+		goto err;
+
+	if (gnttab_alloc_pages(count, add->pages))
+		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->kunmap_ops[i].handle = -1;
+	}
+
+	add->index = 0;
+	add->count = count;
+	atomic_set(&add->users, 1);
+
+	return add;
+
+err:
+	gntdev_free_map(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 gntdev_priv *priv, 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 (populate_freeable_maps && priv) {
+		mutex_lock(&priv->lock);
+		list_del(&map->next);
+		mutex_unlock(&priv->lock);
+	}
+
+	if (map->pages && !use_ptemod)
+		unmap_grant_pages(map, 0, map->count);
+	gntdev_free_map(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;
+
+	/*
+	 * Set the PTE as special to force get_user_pages_fast() fall
+	 * back to the slow path.  If this is not supported as part of
+	 * the grant map, it will be done afterwards.
+	 */
+	if (xen_feature(XENFEAT_gnttab_map_avail_bits))
+		flags |= (1 << _GNTMAP_guest_avail0);
+
+	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;
+}
+
+#ifdef CONFIG_X86
+static int set_grant_ptes_as_special(pte_t *pte, pgtable_t token,
+				     unsigned long addr, void *data)
+{
+	set_pte_at(current->mm, addr, pte, pte_mkspecial(*pte));
+	return 0;
+}
+#endif
+
+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 long address = (unsigned long)
+				pfn_to_kaddr(page_to_pfn(map->pages[i]));
+			BUG_ON(PageHighMem(map->pages[i]));
+
+			gnttab_set_map_op(&map->kmap_ops[i], address,
+				map->flags | GNTMAP_host_map,
+				map->grants[i].ref,
+				map->grants[i].domid);
+			gnttab_set_unmap_op(&map->kunmap_ops[i], address,
+				map->flags | GNTMAP_host_map, -1);
+		}
+	}
+
+	pr_debug("map %d+%d\n", 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;
+			continue;
+		}
+
+		map->unmap_ops[i].handle = map->map_ops[i].handle;
+		if (use_ptemod)
+			map->kunmap_ops[i].handle = map->kmap_ops[i].handle;
+	}
+	return err;
+}
+
+static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
+{
+	int i, err = 0;
+	struct gntab_unmap_queue_data unmap_data;
+
+	if (map->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
+		int pgno = (map->notify.addr >> PAGE_SHIFT);
+		if (pgno >= offset && pgno < offset + pages) {
+			/* No need for kmap, pages are in lowmem */
+			uint8_t *tmp = pfn_to_kaddr(page_to_pfn(map->pages[pgno]));
+			tmp[map->notify.addr & (PAGE_SIZE-1)] = 0;
+			map->notify.flags &= ~UNMAP_NOTIFY_CLEAR_BYTE;
+		}
+	}
+
+	unmap_data.unmap_ops = map->unmap_ops + offset;
+	unmap_data.kunmap_ops = use_ptemod ? map->kunmap_ops + offset : NULL;
+	unmap_data.pages = map->pages + offset;
+	unmap_data.count = pages;
+
+	err = gnttab_unmap_refs_sync(&unmap_data);
+	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\n",
+			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]\n", 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\n", vma);
+	atomic_inc(&map->users);
+}
+
+static void gntdev_vma_close(struct vm_area_struct *vma)
+{
+	struct grant_map *map = vma->vm_private_data;
+	struct file *file = vma->vm_file;
+	struct gntdev_priv *priv = file->private_data;
+
+	pr_debug("gntdev_vma_close %p\n", vma);
+	if (use_ptemod) {
+		/* It is possible that an mmu notifier could be running
+		 * concurrently, so take priv->lock to ensure that the vma won't
+		 * vanishing during the unmap_grant_pages call, since we will
+		 * spin here until that completes. Such a concurrent call will
+		 * not do any unmapping, since that has been done prior to
+		 * closing the vma, but it may still iterate the unmap_ops list.
+		 */
+		mutex_lock(&priv->lock);
+		map->vma = NULL;
+		mutex_unlock(&priv->lock);
+	}
+	vma->vm_private_data = NULL;
+	gntdev_put_map(priv, map);
+}
+
+static struct page *gntdev_vma_find_special_page(struct vm_area_struct *vma,
+						 unsigned long addr)
+{
+	struct grant_map *map = vma->vm_private_data;
+
+	return map->pages[(addr - map->pages_vm_start) >> PAGE_SHIFT];
+}
+
+static struct vm_operations_struct gntdev_vmops = {
+	.open = gntdev_vma_open,
+	.close = gntdev_vma_close,
+	.find_special_page = gntdev_vma_find_special_page,
+};
+
+/* ------------------------------------------------------------------ */
+
+static void unmap_if_in_range(struct grant_map *map,
+			      unsigned long start, unsigned long end)
+{
+	unsigned long mstart, mend;
+	int err;
+
+	if (!map->vma)
+		return;
+	if (map->vma->vm_start >= end)
+		return;
+	if (map->vma->vm_end <= start)
+		return;
+	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\n",
+			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);
+}
+
+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;
+
+	mutex_lock(&priv->lock);
+	list_for_each_entry(map, &priv->maps, next) {
+		unmap_if_in_range(map, start, end);
+	}
+	list_for_each_entry(map, &priv->freeable_maps, next) {
+		unmap_if_in_range(map, start, end);
+	}
+	mutex_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;
+
+	mutex_lock(&priv->lock);
+	list_for_each_entry(map, &priv->maps, next) {
+		if (!map->vma)
+			continue;
+		pr_debug("map %d+%d (%lx %lx)\n",
+				map->index, map->count,
+				map->vma->vm_start, map->vma->vm_end);
+		err = unmap_grant_pages(map, /* offset */ 0, map->count);
+		WARN_ON(err);
+	}
+	list_for_each_entry(map, &priv->freeable_maps, next) {
+		if (!map->vma)
+			continue;
+		pr_debug("map %d+%d (%lx %lx)\n",
+				map->index, map->count,
+				map->vma->vm_start, map->vma->vm_end);
+		err = unmap_grant_pages(map, /* offset */ 0, map->count);
+		WARN_ON(err);
+	}
+	mutex_unlock(&priv->lock);
+}
+
+static 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);
+	INIT_LIST_HEAD(&priv->freeable_maps);
+	mutex_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\n", 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\n", priv);
+
+	while (!list_empty(&priv->maps)) {
+		map = list_entry(priv->maps.next, struct grant_map, next);
+		list_del(&map->next);
+		gntdev_put_map(NULL /* already removed */, map);
+	}
+	WARN_ON(!list_empty(&priv->freeable_maps));
+
+	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\n", 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\n");
+		gntdev_put_map(NULL, map);
+		return err;
+	}
+
+	if (copy_from_user(map->grants, &u->refs,
+			   sizeof(map->grants[0]) * op.count) != 0) {
+		gntdev_put_map(NULL, map);
+		return -EFAULT;
+	}
+
+	mutex_lock(&priv->lock);
+	gntdev_add_map(priv, map);
+	op.index = map->index << PAGE_SHIFT;
+	mutex_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\n", priv, (int)op.index, (int)op.count);
+
+	mutex_lock(&priv->lock);
+	map = gntdev_find_map_index(priv, op.index >> PAGE_SHIFT, op.count);
+	if (map) {
+		list_del(&map->next);
+		if (populate_freeable_maps)
+			list_add_tail(&map->next, &priv->freeable_maps);
+		err = 0;
+	}
+	mutex_unlock(&priv->lock);
+	if (map)
+		gntdev_put_map(priv, 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;
+	int rv = -EINVAL;
+
+	if (copy_from_user(&op, u, sizeof(op)) != 0)
+		return -EFAULT;
+	pr_debug("priv %p, offset for vaddr %lx\n", priv, (unsigned long)op.vaddr);
+
+	down_read(&current->mm->mmap_sem);
+	vma = find_vma(current->mm, op.vaddr);
+	if (!vma || vma->vm_ops != &gntdev_vmops)
+		goto out_unlock;
+
+	map = vma->vm_private_data;
+	if (!map)
+		goto out_unlock;
+
+	op.offset = map->index << PAGE_SHIFT;
+	op.count = map->count;
+	rv = 0;
+
+ out_unlock:
+	up_read(&current->mm->mmap_sem);
+
+	if (rv == 0 && copy_to_user(u, &op, sizeof(op)) != 0)
+		return -EFAULT;
+	return rv;
+}
+
+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;
+
+	mutex_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:
+	mutex_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\n", 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)\n",
+			index, count, vma->vm_start, vma->vm_pgoff);
+
+	mutex_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) {
+		pr_warn("Huh? Other mm?\n");
+		goto unlock_out;
+	}
+
+	atomic_inc(&map->users);
+
+	vma->vm_ops = &gntdev_vmops;
+
+	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
+
+	if (use_ptemod)
+		vma->vm_flags |= VM_DONTCOPY;
+
+	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;
+	}
+
+	mutex_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) {
+			pr_warn("find_grant_ptes() failure.\n");
+			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;
+		}
+	} else {
+#ifdef CONFIG_X86
+		/*
+		 * If the PTEs were not made special by the grant map
+		 * hypercall, do so here.
+		 *
+		 * This is racy since the mapping is already visible
+		 * to userspace but userspace should be well-behaved
+		 * enough to not touch it until the mmap() call
+		 * returns.
+		 */
+		if (!xen_feature(XENFEAT_gnttab_map_avail_bits)) {
+			apply_to_page_range(vma->vm_mm, vma->vm_start,
+					    vma->vm_end - vma->vm_start,
+					    set_grant_ptes_as_special, NULL);
+		}
+#endif
+		map->pages_vm_start = vma->vm_start;
+	}
+
+	return 0;
+
+unlock_out:
+	mutex_unlock(&priv->lock);
+	return err;
+
+out_unlock_put:
+	mutex_unlock(&priv->lock);
+out_put_map:
+	if (use_ptemod)
+		map->vma = NULL;
+	gntdev_put_map(priv, 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_feature(XENFEAT_auto_translated_physmap);
+
+	err = misc_register(&gntdev_miscdev);
+	if (err != 0) {
+		pr_err("Could not register gntdev device\n");
+		return err;
+	}
+	return 0;
+}
+
+static void __exit gntdev_exit(void)
+{
+	misc_deregister(&gntdev_miscdev);
+}
+
+module_init(gntdev_init);
+module_exit(gntdev_exit);
+
+/* ------------------------------------------------------------------ */