Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1175 insertions, 0 deletions

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
new file mode 100644
index 000000000..4d9a3050d
--- /dev/null
+++ b/drivers/xen/gntdev.c
@@ -0,0 +1,1175 @@
+/******************************************************************************
+ * 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>
+ *           (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
+ *
+ * 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/dma-mapping.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/miscdevice.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/sched.h>
+#include <linux/sched/mm.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+#include <linux/highmem.h>
+#include <linux/refcount.h>
+#include <linux/workqueue.h>
+
+#include <xen/xen.h>
+#include <xen/grant_table.h>
+#include <xen/balloon.h>
+#include <xen/gntdev.h>
+#include <xen/events.h>
+#include <xen/page.h>
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/hypercall.h>
+
+#include "gntdev-common.h"
+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+#include "gntdev-dmabuf.h"
+#endif
+
+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 unsigned int limit = 64*1024;
+module_param(limit, uint, 0644);
+MODULE_PARM_DESC(limit,
+	"Maximum number of grants that may be mapped by one mapping request");
+
+/* True in PV mode, false otherwise */
+static int use_ptemod;
+
+static void unmap_grant_pages(struct gntdev_grant_map *map,
+			      int offset, int pages);
+
+static struct miscdevice gntdev_miscdev;
+
+/* ------------------------------------------------------------------ */
+
+bool gntdev_test_page_count(unsigned int count)
+{
+	return !count || count > limit;
+}
+
+static void gntdev_print_maps(struct gntdev_priv *priv,
+			      char *text, int text_index)
+{
+#ifdef DEBUG
+	struct gntdev_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 gntdev_grant_map *map)
+{
+	if (map == NULL)
+		return;
+
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	if (map->dma_vaddr) {
+		struct gnttab_dma_alloc_args args;
+
+		args.dev = map->dma_dev;
+		args.coherent = !!(map->dma_flags & GNTDEV_DMA_FLAG_COHERENT);
+		args.nr_pages = map->count;
+		args.pages = map->pages;
+		args.frames = map->frames;
+		args.vaddr = map->dma_vaddr;
+		args.dev_bus_addr = map->dma_bus_addr;
+
+		gnttab_dma_free_pages(&args);
+	} else
+#endif
+	if (map->pages)
+		gnttab_free_pages(map->count, map->pages);
+
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	kvfree(map->frames);
+#endif
+	kvfree(map->pages);
+	kvfree(map->grants);
+	kvfree(map->map_ops);
+	kvfree(map->unmap_ops);
+	kvfree(map->kmap_ops);
+	kvfree(map->kunmap_ops);
+	kvfree(map->being_removed);
+	kfree(map);
+}
+
+struct gntdev_grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count,
+					  int dma_flags)
+{
+	struct gntdev_grant_map *add;
+	int i;
+
+	add = kzalloc(sizeof(*add), GFP_KERNEL);
+	if (NULL == add)
+		return NULL;
+
+	add->grants    = kvmalloc_array(count, sizeof(add->grants[0]),
+					GFP_KERNEL);
+	add->map_ops   = kvmalloc_array(count, sizeof(add->map_ops[0]),
+					GFP_KERNEL);
+	add->unmap_ops = kvmalloc_array(count, sizeof(add->unmap_ops[0]),
+					GFP_KERNEL);
+	add->pages     = kvcalloc(count, sizeof(add->pages[0]), GFP_KERNEL);
+	add->being_removed =
+		kvcalloc(count, sizeof(add->being_removed[0]), GFP_KERNEL);
+	if (NULL == add->grants    ||
+	    NULL == add->map_ops   ||
+	    NULL == add->unmap_ops ||
+	    NULL == add->pages     ||
+	    NULL == add->being_removed)
+		goto err;
+	if (use_ptemod) {
+		add->kmap_ops   = kvmalloc_array(count, sizeof(add->kmap_ops[0]),
+						 GFP_KERNEL);
+		add->kunmap_ops = kvmalloc_array(count, sizeof(add->kunmap_ops[0]),
+						 GFP_KERNEL);
+		if (NULL == add->kmap_ops || NULL == add->kunmap_ops)
+			goto err;
+	}
+
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	add->dma_flags = dma_flags;
+
+	/*
+	 * Check if this mapping is requested to be backed
+	 * by a DMA buffer.
+	 */
+	if (dma_flags & (GNTDEV_DMA_FLAG_WC | GNTDEV_DMA_FLAG_COHERENT)) {
+		struct gnttab_dma_alloc_args args;
+
+		add->frames = kvcalloc(count, sizeof(add->frames[0]),
+				       GFP_KERNEL);
+		if (!add->frames)
+			goto err;
+
+		/* Remember the device, so we can free DMA memory. */
+		add->dma_dev = priv->dma_dev;
+
+		args.dev = priv->dma_dev;
+		args.coherent = !!(dma_flags & GNTDEV_DMA_FLAG_COHERENT);
+		args.nr_pages = count;
+		args.pages = add->pages;
+		args.frames = add->frames;
+
+		if (gnttab_dma_alloc_pages(&args))
+			goto err;
+
+		add->dma_vaddr = args.vaddr;
+		add->dma_bus_addr = args.dev_bus_addr;
+	} else
+#endif
+	if (gnttab_alloc_pages(count, add->pages))
+		goto err;
+
+	for (i = 0; i < count; i++) {
+		add->grants[i].domid = DOMID_INVALID;
+		add->grants[i].ref = INVALID_GRANT_REF;
+		add->map_ops[i].handle = INVALID_GRANT_HANDLE;
+		add->unmap_ops[i].handle = INVALID_GRANT_HANDLE;
+		if (use_ptemod) {
+			add->kmap_ops[i].handle = INVALID_GRANT_HANDLE;
+			add->kunmap_ops[i].handle = INVALID_GRANT_HANDLE;
+		}
+	}
+
+	add->index = 0;
+	add->count = count;
+	refcount_set(&add->users, 1);
+
+	return add;
+
+err:
+	gntdev_free_map(add);
+	return NULL;
+}
+
+void gntdev_add_map(struct gntdev_priv *priv, struct gntdev_grant_map *add)
+{
+	struct gntdev_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 gntdev_grant_map *gntdev_find_map_index(struct gntdev_priv *priv,
+						      int index, int count)
+{
+	struct gntdev_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;
+}
+
+void gntdev_put_map(struct gntdev_priv *priv, struct gntdev_grant_map *map)
+{
+	if (!map)
+		return;
+
+	if (!refcount_dec_and_test(&map->users))
+		return;
+
+	if (map->pages && !use_ptemod) {
+		/*
+		 * Increment the reference count.  This ensures that the
+		 * subsequent call to unmap_grant_pages() will not wind up
+		 * re-entering itself.  It *can* wind up calling
+		 * gntdev_put_map() recursively, but such calls will be with a
+		 * reference count greater than 1, so they will return before
+		 * this code is reached.  The recursion depth is thus limited to
+		 * 1.  Do NOT use refcount_inc() here, as it will detect that
+		 * the reference count is zero and WARN().
+		 */
+		refcount_set(&map->users, 1);
+
+		/*
+		 * Unmap the grants.  This may or may not be asynchronous, so it
+		 * is possible that the reference count is 1 on return, but it
+		 * could also be greater than 1.
+		 */
+		unmap_grant_pages(map, 0, map->count);
+
+		/* Check if the memory now needs to be freed */
+		if (!refcount_dec_and_test(&map->users))
+			return;
+
+		/*
+		 * All pages have been returned to the hypervisor, so free the
+		 * map.
+		 */
+	}
+
+	if (use_ptemod && map->notifier_init)
+		mmu_interval_notifier_remove(&map->notifier);
+
+	if (map->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
+		notify_remote_via_evtchn(map->notify.event);
+		evtchn_put(map->notify.event);
+	}
+	gntdev_free_map(map);
+}
+
+/* ------------------------------------------------------------------ */
+
+static int find_grant_ptes(pte_t *pte, unsigned long addr, void *data)
+{
+	struct gntdev_grant_map *map = data;
+	unsigned int pgnr = (addr - map->pages_vm_start) >> PAGE_SHIFT;
+	int flags = map->flags | GNTMAP_application_map | GNTMAP_contains_pte |
+		    (1 << _GNTMAP_guest_avail0);
+	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,
+			    INVALID_GRANT_HANDLE);
+	return 0;
+}
+
+int gntdev_map_grant_pages(struct gntdev_grant_map *map)
+{
+	size_t alloced = 0;
+	int i, err = 0;
+
+	if (!use_ptemod) {
+		/* Note: it could already be mapped */
+		if (map->map_ops[0].handle != INVALID_GRANT_HANDLE)
+			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, INVALID_GRANT_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.
+		 * Note that GNTMAP_device_map isn't needed here: The
+		 * dev_bus_addr output field gets consumed only from ->map_ops,
+		 * and by not requesting it when mapping we also avoid needing
+		 * to mirror dev_bus_addr into ->unmap_ops (and holding an extra
+		 * reference to the page in the hypervisor).
+		 */
+		unsigned int flags = (map->flags & ~GNTMAP_device_map) |
+				     GNTMAP_host_map;
+
+		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, flags,
+				map->grants[i].ref,
+				map->grants[i].domid);
+			gnttab_set_unmap_op(&map->kunmap_ops[i], address,
+				flags, INVALID_GRANT_HANDLE);
+		}
+	}
+
+	pr_debug("map %d+%d\n", map->index, map->count);
+	err = gnttab_map_refs(map->map_ops, map->kmap_ops, map->pages,
+			map->count);
+
+	for (i = 0; i < map->count; i++) {
+		if (map->map_ops[i].status == GNTST_okay) {
+			map->unmap_ops[i].handle = map->map_ops[i].handle;
+			alloced++;
+		} else if (!err)
+			err = -EINVAL;
+
+		if (map->flags & GNTMAP_device_map)
+			map->unmap_ops[i].dev_bus_addr = map->map_ops[i].dev_bus_addr;
+
+		if (use_ptemod) {
+			if (map->kmap_ops[i].status == GNTST_okay) {
+				alloced++;
+				map->kunmap_ops[i].handle = map->kmap_ops[i].handle;
+			} else if (!err)
+				err = -EINVAL;
+		}
+	}
+	atomic_add(alloced, &map->live_grants);
+	return err;
+}
+
+static void __unmap_grant_pages_done(int result,
+		struct gntab_unmap_queue_data *data)
+{
+	unsigned int i;
+	struct gntdev_grant_map *map = data->data;
+	unsigned int offset = data->unmap_ops - map->unmap_ops;
+	int successful_unmaps = 0;
+	int live_grants;
+
+	for (i = 0; i < data->count; i++) {
+		if (map->unmap_ops[offset + i].status == GNTST_okay &&
+		    map->unmap_ops[offset + i].handle != INVALID_GRANT_HANDLE)
+			successful_unmaps++;
+
+		WARN_ON(map->unmap_ops[offset + i].status != GNTST_okay &&
+			map->unmap_ops[offset + i].handle != INVALID_GRANT_HANDLE);
+		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 = INVALID_GRANT_HANDLE;
+		if (use_ptemod) {
+			if (map->kunmap_ops[offset + i].status == GNTST_okay &&
+			    map->kunmap_ops[offset + i].handle != INVALID_GRANT_HANDLE)
+				successful_unmaps++;
+
+			WARN_ON(map->kunmap_ops[offset + i].status != GNTST_okay &&
+				map->kunmap_ops[offset + i].handle != INVALID_GRANT_HANDLE);
+			pr_debug("kunmap handle=%u st=%d\n",
+				 map->kunmap_ops[offset+i].handle,
+				 map->kunmap_ops[offset+i].status);
+			map->kunmap_ops[offset+i].handle = INVALID_GRANT_HANDLE;
+		}
+	}
+
+	/*
+	 * Decrease the live-grant counter.  This must happen after the loop to
+	 * prevent premature reuse of the grants by gnttab_mmap().
+	 */
+	live_grants = atomic_sub_return(successful_unmaps, &map->live_grants);
+	if (WARN_ON(live_grants < 0))
+		pr_err("%s: live_grants became negative (%d) after unmapping %d pages!\n",
+		       __func__, live_grants, successful_unmaps);
+
+	/* Release reference taken by __unmap_grant_pages */
+	gntdev_put_map(NULL, map);
+}
+
+static void __unmap_grant_pages(struct gntdev_grant_map *map, int offset,
+			       int pages)
+{
+	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;
+		}
+	}
+
+	map->unmap_data.unmap_ops = map->unmap_ops + offset;
+	map->unmap_data.kunmap_ops = use_ptemod ? map->kunmap_ops + offset : NULL;
+	map->unmap_data.pages = map->pages + offset;
+	map->unmap_data.count = pages;
+	map->unmap_data.done = __unmap_grant_pages_done;
+	map->unmap_data.data = map;
+	refcount_inc(&map->users); /* to keep map alive during async call below */
+
+	gnttab_unmap_refs_async(&map->unmap_data);
+}
+
+static void unmap_grant_pages(struct gntdev_grant_map *map, int offset,
+			      int pages)
+{
+	int range;
+
+	if (atomic_read(&map->live_grants) == 0)
+		return; /* Nothing to do */
+
+	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) {
+		while (pages && map->being_removed[offset]) {
+			offset++;
+			pages--;
+		}
+		range = 0;
+		while (range < pages) {
+			if (map->being_removed[offset + range])
+				break;
+			map->being_removed[offset + range] = true;
+			range++;
+		}
+		if (range)
+			__unmap_grant_pages(map, offset, range);
+		offset += range;
+		pages -= range;
+	}
+}
+
+/* ------------------------------------------------------------------ */
+
+static void gntdev_vma_open(struct vm_area_struct *vma)
+{
+	struct gntdev_grant_map *map = vma->vm_private_data;
+
+	pr_debug("gntdev_vma_open %p\n", vma);
+	refcount_inc(&map->users);
+}
+
+static void gntdev_vma_close(struct vm_area_struct *vma)
+{
+	struct gntdev_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);
+
+	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 gntdev_grant_map *map = vma->vm_private_data;
+
+	return map->pages[(addr - map->pages_vm_start) >> PAGE_SHIFT];
+}
+
+static const struct vm_operations_struct gntdev_vmops = {
+	.open = gntdev_vma_open,
+	.close = gntdev_vma_close,
+	.find_special_page = gntdev_vma_find_special_page,
+};
+
+/* ------------------------------------------------------------------ */
+
+static bool gntdev_invalidate(struct mmu_interval_notifier *mn,
+			      const struct mmu_notifier_range *range,
+			      unsigned long cur_seq)
+{
+	struct gntdev_grant_map *map =
+		container_of(mn, struct gntdev_grant_map, notifier);
+	unsigned long mstart, mend;
+	unsigned long map_start, map_end;
+
+	if (!mmu_notifier_range_blockable(range))
+		return false;
+
+	map_start = map->pages_vm_start;
+	map_end = map->pages_vm_start + (map->count << PAGE_SHIFT);
+
+	/*
+	 * If the VMA is split or otherwise changed the notifier is not
+	 * updated, but we don't want to process VA's outside the modified
+	 * VMA. FIXME: It would be much more understandable to just prevent
+	 * modifying the VMA in the first place.
+	 */
+	if (map_start >= range->end || map_end <= range->start)
+		return true;
+
+	mstart = max(range->start, map_start);
+	mend = min(range->end, map_end);
+	pr_debug("map %d+%d (%lx %lx), range %lx %lx, mrange %lx %lx\n",
+		 map->index, map->count, map_start, map_end,
+		 range->start, range->end, mstart, mend);
+	unmap_grant_pages(map, (mstart - map_start) >> PAGE_SHIFT,
+			  (mend - mstart) >> PAGE_SHIFT);
+
+	return true;
+}
+
+static const struct mmu_interval_notifier_ops gntdev_mmu_ops = {
+	.invalidate = gntdev_invalidate,
+};
+
+/* ------------------------------------------------------------------ */
+
+static int gntdev_open(struct inode *inode, struct file *flip)
+{
+	struct gntdev_priv *priv;
+
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&priv->maps);
+	mutex_init(&priv->lock);
+
+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+	priv->dmabuf_priv = gntdev_dmabuf_init(flip);
+	if (IS_ERR(priv->dmabuf_priv)) {
+		int ret = PTR_ERR(priv->dmabuf_priv);
+
+		kfree(priv);
+		return ret;
+	}
+#endif
+
+	flip->private_data = priv;
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	priv->dma_dev = gntdev_miscdev.this_device;
+	dma_coerce_mask_and_coherent(priv->dma_dev, DMA_BIT_MASK(64));
+#endif
+	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 gntdev_grant_map *map;
+
+	pr_debug("priv %p\n", priv);
+
+	mutex_lock(&priv->lock);
+	while (!list_empty(&priv->maps)) {
+		map = list_entry(priv->maps.next,
+				 struct gntdev_grant_map, next);
+		list_del(&map->next);
+		gntdev_put_map(NULL /* already removed */, map);
+	}
+	mutex_unlock(&priv->lock);
+
+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+	gntdev_dmabuf_fini(priv->dmabuf_priv);
+#endif
+
+	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 gntdev_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(gntdev_test_page_count(op.count)))
+		return -EINVAL;
+
+	err = -ENOMEM;
+	map = gntdev_alloc_map(priv, op.count, 0 /* This is not a dma-buf. */);
+	if (!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 gntdev_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);
+		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 gntdev_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);
+
+	mmap_read_lock(current->mm);
+	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:
+	mmap_read_unlock(current->mm);
+
+	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 gntdev_grant_map *map;
+	int rc;
+	int out_flags;
+	evtchn_port_t 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;
+}
+
+#define GNTDEV_COPY_BATCH 16
+
+struct gntdev_copy_batch {
+	struct gnttab_copy ops[GNTDEV_COPY_BATCH];
+	struct page *pages[GNTDEV_COPY_BATCH];
+	s16 __user *status[GNTDEV_COPY_BATCH];
+	unsigned int nr_ops;
+	unsigned int nr_pages;
+	bool writeable;
+};
+
+static int gntdev_get_page(struct gntdev_copy_batch *batch, void __user *virt,
+				unsigned long *gfn)
+{
+	unsigned long addr = (unsigned long)virt;
+	struct page *page;
+	unsigned long xen_pfn;
+	int ret;
+
+	ret = pin_user_pages_fast(addr, 1, batch->writeable ? FOLL_WRITE : 0, &page);
+	if (ret < 0)
+		return ret;
+
+	batch->pages[batch->nr_pages++] = page;
+
+	xen_pfn = page_to_xen_pfn(page) + XEN_PFN_DOWN(addr & ~PAGE_MASK);
+	*gfn = pfn_to_gfn(xen_pfn);
+
+	return 0;
+}
+
+static void gntdev_put_pages(struct gntdev_copy_batch *batch)
+{
+	unpin_user_pages_dirty_lock(batch->pages, batch->nr_pages, batch->writeable);
+	batch->nr_pages = 0;
+	batch->writeable = false;
+}
+
+static int gntdev_copy(struct gntdev_copy_batch *batch)
+{
+	unsigned int i;
+
+	gnttab_batch_copy(batch->ops, batch->nr_ops);
+	gntdev_put_pages(batch);
+
+	/*
+	 * For each completed op, update the status if the op failed
+	 * and all previous ops for the segment were successful.
+	 */
+	for (i = 0; i < batch->nr_ops; i++) {
+		s16 status = batch->ops[i].status;
+		s16 old_status;
+
+		if (status == GNTST_okay)
+			continue;
+
+		if (__get_user(old_status, batch->status[i]))
+			return -EFAULT;
+
+		if (old_status != GNTST_okay)
+			continue;
+
+		if (__put_user(status, batch->status[i]))
+			return -EFAULT;
+	}
+
+	batch->nr_ops = 0;
+	return 0;
+}
+
+static int gntdev_grant_copy_seg(struct gntdev_copy_batch *batch,
+				 struct gntdev_grant_copy_segment *seg,
+				 s16 __user *status)
+{
+	uint16_t copied = 0;
+
+	/*
+	 * Disallow local -> local copies since there is only space in
+	 * batch->pages for one page per-op and this would be a very
+	 * expensive memcpy().
+	 */
+	if (!(seg->flags & (GNTCOPY_source_gref | GNTCOPY_dest_gref)))
+		return -EINVAL;
+
+	/* Can't cross page if source/dest is a grant ref. */
+	if (seg->flags & GNTCOPY_source_gref) {
+		if (seg->source.foreign.offset + seg->len > XEN_PAGE_SIZE)
+			return -EINVAL;
+	}
+	if (seg->flags & GNTCOPY_dest_gref) {
+		if (seg->dest.foreign.offset + seg->len > XEN_PAGE_SIZE)
+			return -EINVAL;
+	}
+
+	if (put_user(GNTST_okay, status))
+		return -EFAULT;
+
+	while (copied < seg->len) {
+		struct gnttab_copy *op;
+		void __user *virt;
+		size_t len, off;
+		unsigned long gfn;
+		int ret;
+
+		if (batch->nr_ops >= GNTDEV_COPY_BATCH) {
+			ret = gntdev_copy(batch);
+			if (ret < 0)
+				return ret;
+		}
+
+		len = seg->len - copied;
+
+		op = &batch->ops[batch->nr_ops];
+		op->flags = 0;
+
+		if (seg->flags & GNTCOPY_source_gref) {
+			op->source.u.ref = seg->source.foreign.ref;
+			op->source.domid = seg->source.foreign.domid;
+			op->source.offset = seg->source.foreign.offset + copied;
+			op->flags |= GNTCOPY_source_gref;
+		} else {
+			virt = seg->source.virt + copied;
+			off = (unsigned long)virt & ~XEN_PAGE_MASK;
+			len = min(len, (size_t)XEN_PAGE_SIZE - off);
+			batch->writeable = false;
+
+			ret = gntdev_get_page(batch, virt, &gfn);
+			if (ret < 0)
+				return ret;
+
+			op->source.u.gmfn = gfn;
+			op->source.domid = DOMID_SELF;
+			op->source.offset = off;
+		}
+
+		if (seg->flags & GNTCOPY_dest_gref) {
+			op->dest.u.ref = seg->dest.foreign.ref;
+			op->dest.domid = seg->dest.foreign.domid;
+			op->dest.offset = seg->dest.foreign.offset + copied;
+			op->flags |= GNTCOPY_dest_gref;
+		} else {
+			virt = seg->dest.virt + copied;
+			off = (unsigned long)virt & ~XEN_PAGE_MASK;
+			len = min(len, (size_t)XEN_PAGE_SIZE - off);
+			batch->writeable = true;
+
+			ret = gntdev_get_page(batch, virt, &gfn);
+			if (ret < 0)
+				return ret;
+
+			op->dest.u.gmfn = gfn;
+			op->dest.domid = DOMID_SELF;
+			op->dest.offset = off;
+		}
+
+		op->len = len;
+		copied += len;
+
+		batch->status[batch->nr_ops] = status;
+		batch->nr_ops++;
+	}
+
+	return 0;
+}
+
+static long gntdev_ioctl_grant_copy(struct gntdev_priv *priv, void __user *u)
+{
+	struct ioctl_gntdev_grant_copy copy;
+	struct gntdev_copy_batch batch;
+	unsigned int i;
+	int ret = 0;
+
+	if (copy_from_user(&copy, u, sizeof(copy)))
+		return -EFAULT;
+
+	batch.nr_ops = 0;
+	batch.nr_pages = 0;
+
+	for (i = 0; i < copy.count; i++) {
+		struct gntdev_grant_copy_segment seg;
+
+		if (copy_from_user(&seg, &copy.segments[i], sizeof(seg))) {
+			ret = -EFAULT;
+			goto out;
+		}
+
+		ret = gntdev_grant_copy_seg(&batch, &seg, &copy.segments[i].status);
+		if (ret < 0)
+			goto out;
+
+		cond_resched();
+	}
+	if (batch.nr_ops)
+		ret = gntdev_copy(&batch);
+	return ret;
+
+  out:
+	gntdev_put_pages(&batch);
+	return ret;
+}
+
+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);
+
+	case IOCTL_GNTDEV_GRANT_COPY:
+		return gntdev_ioctl_grant_copy(priv, ptr);
+
+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+	case IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS:
+		return gntdev_ioctl_dmabuf_exp_from_refs(priv, use_ptemod, ptr);
+
+	case IOCTL_GNTDEV_DMABUF_EXP_WAIT_RELEASED:
+		return gntdev_ioctl_dmabuf_exp_wait_released(priv, ptr);
+
+	case IOCTL_GNTDEV_DMABUF_IMP_TO_REFS:
+		return gntdev_ioctl_dmabuf_imp_to_refs(priv, ptr);
+
+	case IOCTL_GNTDEV_DMABUF_IMP_RELEASE:
+		return gntdev_ioctl_dmabuf_imp_release(priv, ptr);
+#endif
+
+	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_pages(vma);
+	struct gntdev_grant_map *map;
+	int 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 (!atomic_add_unless(&map->in_use, 1, 1))
+		goto unlock_out;
+
+	refcount_inc(&map->users);
+
+	vma->vm_ops = &gntdev_vmops;
+
+	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_MIXEDMAP;
+
+	if (use_ptemod)
+		vma->vm_flags |= VM_DONTCOPY;
+
+	vma->vm_private_data = map;
+	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;
+	}
+
+	map->pages_vm_start = vma->vm_start;
+
+	if (use_ptemod) {
+		err = mmu_interval_notifier_insert_locked(
+			&map->notifier, vma->vm_mm, vma->vm_start,
+			vma->vm_end - vma->vm_start, &gntdev_mmu_ops);
+		if (err)
+			goto out_unlock_put;
+
+		map->notifier_init = true;
+	}
+	mutex_unlock(&priv->lock);
+
+	if (use_ptemod) {
+		/*
+		 * gntdev takes the address of the PTE in find_grant_ptes() and
+		 * passes it to the hypervisor in gntdev_map_grant_pages(). The
+		 * purpose of the notifier is to prevent the hypervisor pointer
+		 * to the PTE from going stale.
+		 *
+		 * Since this vma's mappings can't be touched without the
+		 * mmap_lock, and we are holding it now, there is no need for
+		 * the notifier_range locking pattern.
+		 */
+		mmu_interval_read_begin(&map->notifier);
+
+		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 = gntdev_map_grant_pages(map);
+	if (err)
+		goto out_put_map;
+
+	if (!use_ptemod) {
+		err = vm_map_pages_zero(vma, map->pages, map->count);
+		if (err)
+			goto out_put_map;
+	}
+
+	return 0;
+
+unlock_out:
+	mutex_unlock(&priv->lock);
+	return err;
+
+out_unlock_put:
+	mutex_unlock(&priv->lock);
+out_put_map:
+	if (use_ptemod)
+		unmap_grant_pages(map, 0, map->count);
+	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);
+
+/* ------------------------------------------------------------------ */