/*
* Copyright © 2012-2014 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
*/
#include "drmP.h"
#include "i915_drm.h"
#include "i915_drv.h"
#include "i915_trace.h"
#include "intel_drv.h"
#include <linux/mmu_context.h>
#include <linux/mmu_notifier.h>
#include <linux/mempolicy.h>
#include <linux/swap.h>
struct i915_mm_struct {
struct mm_struct *mm;
struct drm_device *dev;
struct i915_mmu_notifier *mn;
struct hlist_node node;
struct kref kref;
struct work_struct work;
};
#if defined(CONFIG_MMU_NOTIFIER)
#include <linux/interval_tree.h>
struct i915_mmu_notifier {
spinlock_t lock;
struct hlist_node node;
struct mmu_notifier mn;
struct rb_root objects;
struct list_head linear;
unsigned long serial;
bool has_linear;
};
struct i915_mmu_object {
struct i915_mmu_notifier *mn;
struct interval_tree_node it;
struct list_head link;
struct drm_i915_gem_object *obj;
bool is_linear;
};
static unsigned long cancel_userptr(struct drm_i915_gem_object *obj)
{
struct drm_device *dev = obj->base.dev;
unsigned long end;
mutex_lock(&dev->struct_mutex);
/* Cancel any active worker and force us to re-evaluate gup */
obj->userptr.work = NULL;
if (obj->pages != NULL) {
struct drm_i915_private *dev_priv = to_i915(dev);
struct i915_vma *vma, *tmp;
bool was_interruptible;
was_interruptible = dev_priv->mm.interruptible;
dev_priv->mm.interruptible = false;
list_for_each_entry_safe(vma, tmp, &obj->vma_list, vma_link) {
int ret = i915_vma_unbind(vma);
WARN_ON(ret && ret != -EIO);
}
WARN_ON(i915_gem_object_put_pages(obj));
dev_priv->mm.interruptible = was_interruptible;
}
end = obj->userptr.ptr + obj->base.size;
drm_gem_object_unreference(&obj->base);
mutex_unlock(&dev->struct_mutex);
return end;
}
static void *invalidate_range__linear(struct i915_mmu_notifier *mn,
struct mm_struct *mm,
unsigned long start,
unsigned long end)
{
struct i915_mmu_object *mo;
unsigned long serial;
restart:
serial = mn->serial;
list_for_each_entry(mo, &mn->linear, link) {
struct drm_i915_gem_object *obj;
if (mo->it.last < start || mo->it.start > end)
continue;
obj = mo->obj;
if (!kref_get_unless_zero(&obj->base.refcount))
continue;
spin_unlock(&mn->lock);
cancel_userptr(obj);
spin_lock(&mn->lock);
if (serial != mn->serial)
goto restart;
}
return NULL;
}
static void i915_gem_userptr_mn_invalidate_range_start(struct mmu_notifier *_mn,
struct mm_struct *mm,
unsigned long start,
unsigned long end)
{
struct i915_mmu_notifier *mn = container_of(_mn, struct i915_mmu_notifier, mn);
struct interval_tree_node *it = NULL;
unsigned long next = start;
unsigned long serial = 0;
end--; /* interval ranges are inclusive, but invalidate range is exclusive */
while (next < end) {
struct drm_i915_gem_object *obj = NULL;
spin_lock(&mn->lock);
if (mn->has_linear)
it = invalidate_range__linear(mn, mm, start, end);
else if (serial == mn->serial)
it = interval_tree_iter_next(it, next, end);
else
it = interval_tree_iter_first(&mn->objects, start, end);
if (it != NULL) {
obj = container_of(it, struct i915_mmu_object, it)->obj;
/* The mmu_object is released late when destroying the
* GEM object so it is entirely possible to gain a
* reference on an object in the process of being freed
* since our serialisation is via the spinlock and not
* the struct_mutex - and consequently use it after it
* is freed and then double free it.
*/
if (!kref_get_unless_zero(&obj->base.refcount)) {
spin_unlock(&mn->lock);
serial = 0;
continue;
}
serial = mn->serial;
}
spin_unlock(&mn->lock);
if (obj == NULL)
return;
next = cancel_userptr(obj);
}
}
static const struct mmu_notifier_ops i915_gem_userptr_notifier = {
.invalidate_range_start = i915_gem_userptr_mn_invalidate_range_start,
};
static struct i915_mmu_notifier *
i915_mmu_notifier_create(struct mm_struct *mm)
{
struct i915_mmu_notifier *mn;
int ret;
mn = kmalloc(sizeof(*mn), GFP_KERNEL);
if (mn == NULL)
return ERR_PTR(-ENOMEM);
spin_lock_init(&mn->lock);
mn->mn.ops = &i915_gem_userptr_notifier;
mn->objects = RB_ROOT;
mn->serial = 1;
INIT_LIST_HEAD(&mn->linear);
mn->has_linear = false;
/* Protected by mmap_sem (write-lock) */
ret = __mmu_notifier_register(&mn->mn, mm);
if (ret) {
kfree(mn);
return ERR_PTR(ret);
}
return mn;
}
static void __i915_mmu_notifier_update_serial(struct i915_mmu_notifier *mn)
{
if (++mn->serial == 0)
mn->serial = 1;
}
static int
i915_mmu_notifier_add(struct drm_device *dev,
struct i915_mmu_notifier *mn,
struct i915_mmu_object *mo)
{
struct interval_tree_node *it;
int ret;
ret = i915_mutex_lock_interruptible(dev);
if (ret)
return ret;
/* Make sure we drop the final active reference (and thereby
* remove the objects from the interval tree) before we do
* the check for overlapping objects.
*/
i915_gem_retire_requests(dev);
spin_lock(&mn->lock);
it = interval_tree_iter_first(&mn->objects,
mo->it.start, mo->it.last);
if (it) {
struct drm_i915_gem_object *obj;
/* We only need to check the first object in the range as it
* either has cancelled gup work queued and we need to
* return back to the user to give time for the gup-workers
* to flush their object references upon which the object will
* be removed from the interval-tree, or the the range is
* still in use by another client and the overlap is invalid.
*
* If we do have an overlap, we cannot use the interval tree
* for fast range invalidation.
*/
obj = container_of(it, struct i915_mmu_object, it)->obj;
if (!obj->userptr.workers)
mn->has_linear = mo->is_linear = true;
else
ret = -EAGAIN;
} else
interval_tree_insert(&mo->it, &mn->objects);
if (ret == 0) {
list_add(&mo->link, &mn->linear);
__i915_mmu_notifier_update_serial(mn);
}
spin_unlock(&mn->lock);
mutex_unlock(&dev->struct_mutex);
return ret;
}
static bool i915_mmu_notifier_has_linear(struct i915_mmu_notifier *mn)
{
struct i915_mmu_object *mo;
list_for_each_entry(mo, &mn->linear, link)
if (mo->is_linear)
return true;
return false;
}
static void
i915_mmu_notifier_del(struct i915_mmu_notifier *mn,
struct i915_mmu_object *mo)
{
spin_lock(&mn->lock);
list_del(&mo->link);
if (mo->is_linear)
mn->has_linear = i915_mmu_notifier_has_linear(mn);
else
interval_tree_remove(&mo->it, &mn->objects);
__i915_mmu_notifier_update_serial(mn);
spin_unlock(&mn->lock);
}
static void
i915_gem_userptr_release__mmu_notifier(struct drm_i915_gem_object *obj)
{
struct i915_mmu_object *mo;
mo = obj->userptr.mmu_object;
if (mo == NULL)
return;
i915_mmu_notifier_del(mo->mn, mo);
kfree(mo);
obj->userptr.mmu_object = NULL;
}
static struct i915_mmu_notifier *
i915_mmu_notifier_find(struct i915_mm_struct *mm)
{
struct i915_mmu_notifier *mn = mm->mn;
mn = mm->mn;
if (mn)
return mn;
down_write(&mm->mm->mmap_sem);
mutex_lock(&to_i915(mm->dev)->mm_lock);
if ((mn = mm->mn) == NULL) {
mn = i915_mmu_notifier_create(mm->mm);
if (!IS_ERR(mn))
mm->mn = mn;
}
mutex_unlock(&to_i915(mm->dev)->mm_lock);
up_write(&mm->mm->mmap_sem);
return mn;
}
static int
i915_gem_userptr_init__mmu_notifier(struct drm_i915_gem_object *obj,
unsigned flags)
{
struct i915_mmu_notifier *mn;
struct i915_mmu_object *mo;
int ret;
if (flags & I915_USERPTR_UNSYNCHRONIZED)
return capable(CAP_SYS_ADMIN) ? 0 : -EPERM;
if (WARN_ON(obj->userptr.mm == NULL))
return -EINVAL;
mn = i915_mmu_notifier_find(obj->userptr.mm);
if (IS_ERR(mn))
return PTR_ERR(mn);
mo = kzalloc(sizeof(*mo), GFP_KERNEL);
if (mo == NULL)
return -ENOMEM;
mo->mn = mn;
mo->it.start = obj->userptr.ptr;
mo->it.last = mo->it.start + obj->base.size - 1;
mo->obj = obj;
ret = i915_mmu_notifier_add(obj->base.dev, mn, mo);
if (ret) {
kfree(mo);
return ret;
}
obj->userptr.mmu_object = mo;
return 0;
}
static void
i915_mmu_notifier_free(struct i915_mmu_notifier *mn,
struct mm_struct *mm)
{
if (mn == NULL)
return;
mmu_notifier_unregister(&mn->mn, mm);
kfree(mn);
}
#else
static void
i915_gem_userptr_release__mmu_notifier(struct drm_i915_gem_object *obj)
{
}
static int
i915_gem_userptr_init__mmu_notifier(struct drm_i915_gem_object *obj,
unsigned flags)
{
if ((flags & I915_USERPTR_UNSYNCHRONIZED) == 0)
return -ENODEV;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
return 0;
}
static void
i915_mmu_notifier_free(struct i915_mmu_notifier *mn,
struct mm_struct *mm)
{
}
#endif
static struct i915_mm_struct *
__i915_mm_struct_find(struct drm_i915_private *dev_priv, struct mm_struct *real)
{
struct i915_mm_struct *mm;
/* Protected by dev_priv->mm_lock */
hash_for_each_possible(dev_priv->mm_structs, mm, node, (unsigned long)real)
if (mm->mm == real)
return mm;
return NULL;
}
static int
i915_gem_userptr_init__mm_struct(struct drm_i915_gem_object *obj)
{
struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
struct i915_mm_struct *mm;
int ret = 0;
/* During release of the GEM object we hold the struct_mutex. This
* precludes us from calling mmput() at that time as that may be
* the last reference and so call exit_mmap(). exit_mmap() will
* attempt to reap the vma, and if we were holding a GTT mmap
* would then call drm_gem_vm_close() and attempt to reacquire
* the struct mutex. So in order to avoid that recursion, we have
* to defer releasing the mm reference until after we drop the
* struct_mutex, i.e. we need to schedule a worker to do the clean
* up.
*/
mutex_lock(&dev_priv->mm_lock);
mm = __i915_mm_struct_find(dev_priv, current->mm);
if (mm == NULL) {
mm = kmalloc(sizeof(*mm), GFP_KERNEL);
if (mm == NULL) {
ret = -ENOMEM;
goto out;
}
kref_init(&mm->kref);
mm->dev = obj->base.dev;
mm->mm = current->mm;
atomic_inc(¤t->mm->mm_count);
mm->mn = NULL;
/* Protected by dev_priv->mm_lock */
hash_add(dev_priv->mm_structs,
&mm->node, (unsigned long)mm->mm);
} else
kref_get(&mm->kref);
obj->userptr.mm = mm;
out:
mutex_unlock(&dev_priv->mm_lock);
return ret;
}
static void
__i915_mm_struct_free__worker(struct work_struct *work)
{
struct i915_mm_struct *mm = container_of(work, typeof(*mm), work);
i915_mmu_notifier_free(mm->mn, mm->mm);
mmdrop(mm->mm);
kfree(mm);
}
static void
__i915_mm_struct_free(struct kref *kref)
{
struct i915_mm_struct *mm = container_of(kref, typeof(*mm), kref);
/* Protected by dev_priv->mm_lock */
hash_del(&mm->node);
mutex_unlock(&to_i915(mm->dev)->mm_lock);
INIT_WORK(&mm->work, __i915_mm_struct_free__worker);
schedule_work(&mm->work);
}
static void
i915_gem_userptr_release__mm_struct(struct drm_i915_gem_object *obj)
{
if (obj->userptr.mm == NULL)
return;
kref_put_mutex(&obj->userptr.mm->kref,
__i915_mm_struct_free,
&to_i915(obj->base.dev)->mm_lock);
obj->userptr.mm = NULL;
}
struct get_pages_work {
struct work_struct work;
struct drm_i915_gem_object *obj;
struct task_struct *task;
};
#if IS_ENABLED(CONFIG_SWIOTLB)
#define swiotlb_active() swiotlb_nr_tbl()
#else
#define swiotlb_active() 0
#endif
static int
st_set_pages(struct sg_table **st, struct page **pvec, int num_pages)
{
struct scatterlist *sg;
int ret, n;
*st = kmalloc(sizeof(**st), GFP_KERNEL);
if (*st == NULL)
return -ENOMEM;
if (swiotlb_active()) {
ret = sg_alloc_table(*st, num_pages, GFP_KERNEL);
if (ret)
goto err;
for_each_sg((*st)->sgl, sg, num_pages, n)
sg_set_page(sg, pvec[n], PAGE_SIZE, 0);
} else {
ret = sg_alloc_table_from_pages(*st, pvec, num_pages,
0, num_pages << PAGE_SHIFT,
GFP_KERNEL);
if (ret)
goto err;
}
return 0;
err:
kfree(*st);
*st = NULL;
return ret;
}
static void
__i915_gem_userptr_get_pages_worker(struct work_struct *_work)
{
struct get_pages_work *work = container_of(_work, typeof(*work), work);
struct drm_i915_gem_object *obj = work->obj;
struct drm_device *dev = obj->base.dev;
const int num_pages = obj->base.size >> PAGE_SHIFT;
struct page **pvec;
int pinned, ret;
ret = -ENOMEM;
pinned = 0;
pvec = kmalloc(num_pages*sizeof(struct page *),
GFP_TEMPORARY | __GFP_NOWARN | __GFP_NORETRY);
if (pvec == NULL)
pvec = drm_malloc_ab(num_pages, sizeof(struct page *));
if (pvec != NULL) {
struct mm_struct *mm = obj->userptr.mm->mm;
down_read(&mm->mmap_sem);
while (pinned < num_pages) {
ret = get_user_pages(work->task, mm,
obj->userptr.ptr + pinned * PAGE_SIZE,
num_pages - pinned,
!obj->userptr.read_only, 0,
pvec + pinned, NULL);
if (ret < 0)
break;
pinned += ret;
}
up_read(&mm->mmap_sem);
}
mutex_lock(&dev->struct_mutex);
if (obj->userptr.work != &work->work) {
ret = 0;
} else if (pinned == num_pages) {
ret = st_set_pages(&obj->pages, pvec, num_pages);
if (ret == 0) {
list_add_tail(&obj->global_list, &to_i915(dev)->mm.unbound_list);
pinned = 0;
}
}
obj->userptr.work = ERR_PTR(ret);
obj->userptr.workers--;
drm_gem_object_unreference(&obj->base);
mutex_unlock(&dev->struct_mutex);
release_pages(pvec, pinned, 0);
drm_free_large(pvec);
put_task_struct(work->task);
kfree(work);
}
static int
i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
{
const int num_pages = obj->base.size >> PAGE_SHIFT;
struct page **pvec;
int pinned, ret;
/* If userspace should engineer that these pages are replaced in
* the vma between us binding this page into the GTT and completion
* of rendering... Their loss. If they change the mapping of their
* pages they need to create a new bo to point to the new vma.
*
* However, that still leaves open the possibility of the vma
* being copied upon fork. Which falls under the same userspace
* synchronisation issue as a regular bo, except that this time
* the process may not be expecting that a particular piece of
* memory is tied to the GPU.
*
* Fortunately, we can hook into the mmu_notifier in order to
* discard the page references prior to anything nasty happening
* to the vma (discard or cloning) which should prevent the more
* egregious cases from causing harm.
*/
pvec = NULL;
pinned = 0;
if (obj->userptr.mm->mm == current->mm) {
pvec = kmalloc(num_pages*sizeof(struct page *),
GFP_TEMPORARY | __GFP_NOWARN | __GFP_NORETRY);
if (pvec == NULL) {
pvec = drm_malloc_ab(num_pages, sizeof(struct page *));
if (pvec == NULL)
return -ENOMEM;
}
pinned = __get_user_pages_fast(obj->userptr.ptr, num_pages,
!obj->userptr.read_only, pvec);
}
if (pinned < num_pages) {
if (pinned < 0) {
ret = pinned;
pinned = 0;
} else {
/* Spawn a worker so that we can acquire the
* user pages without holding our mutex. Access
* to the user pages requires mmap_sem, and we have
* a strict lock ordering of mmap_sem, struct_mutex -
* we already hold struct_mutex here and so cannot
* call gup without encountering a lock inversion.
*
* Userspace will keep on repeating the operation
* (thanks to EAGAIN) until either we hit the fast
* path or the worker completes. If the worker is
* cancelled or superseded, the task is still run
* but the results ignored. (This leads to
* complications that we may have a stray object
* refcount that we need to be wary of when
* checking for existing objects during creation.)
* If the worker encounters an error, it reports
* that error back to this function through
* obj->userptr.work = ERR_PTR.
*/
ret = -EAGAIN;
if (obj->userptr.work == NULL &&
obj->userptr.workers < I915_GEM_USERPTR_MAX_WORKERS) {
struct get_pages_work *work;
work = kmalloc(sizeof(*work), GFP_KERNEL);
if (work != NULL) {
obj->userptr.work = &work->work;
obj->userptr.workers++;
work->obj = obj;
drm_gem_object_reference(&obj->base);
work->task = current;
get_task_struct(work->task);
INIT_WORK(&work->work, __i915_gem_userptr_get_pages_worker);
schedule_work(&work->work);
} else
ret = -ENOMEM;
} else {
if (IS_ERR(obj->userptr.work)) {
ret = PTR_ERR(obj->userptr.work);
obj->userptr.work = NULL;
}
}
}
} else {
ret = st_set_pages(&obj->pages, pvec, num_pages);
if (ret == 0) {
obj->userptr.work = NULL;
pinned = 0;
}
}
release_pages(pvec, pinned, 0);
drm_free_large(pvec);
return ret;
}
static void
i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj)
{
struct sg_page_iter sg_iter;
BUG_ON(obj->userptr.work != NULL);
if (obj->madv != I915_MADV_WILLNEED)
obj->dirty = 0;
for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0) {
struct page *page = sg_page_iter_page(&sg_iter);
if (obj->dirty)
set_page_dirty(page);
mark_page_accessed(page);
page_cache_release(page);
}
obj->dirty = 0;
sg_free_table(obj->pages);
kfree(obj->pages);
}
static void
i915_gem_userptr_release(struct drm_i915_gem_object *obj)
{
i915_gem_userptr_release__mmu_notifier(obj);
i915_gem_userptr_release__mm_struct(obj);
}
static int
i915_gem_userptr_dmabuf_export(struct drm_i915_gem_object *obj)
{
if (obj->userptr.mmu_object)
return 0;
return i915_gem_userptr_init__mmu_notifier(obj, 0);
}
static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = {
.dmabuf_export = i915_gem_userptr_dmabuf_export,
.get_pages = i915_gem_userptr_get_pages,
.put_pages = i915_gem_userptr_put_pages,
.release = i915_gem_userptr_release,
};
/**
* Creates a new mm object that wraps some normal memory from the process
* context - user memory.
*
* We impose several restrictions upon the memory being mapped
* into the GPU.
* 1. It must be page aligned (both start/end addresses, i.e ptr and size).
* 2. It must be normal system memory, not a pointer into another map of IO
* space (e.g. it must not be a GTT mmapping of another object).
* 3. We only allow a bo as large as we could in theory map into the GTT,
* that is we limit the size to the total size of the GTT.
* 4. The bo is marked as being snoopable. The backing pages are left
* accessible directly by the CPU, but reads and writes by the GPU may
* incur the cost of a snoop (unless you have an LLC architecture).
*
* Synchronisation between multiple users and the GPU is left to userspace
* through the normal set-domain-ioctl. The kernel will enforce that the
* GPU relinquishes the VMA before it is returned back to the system
* i.e. upon free(), munmap() or process termination. However, the userspace
* malloc() library may not immediately relinquish the VMA after free() and
* instead reuse it whilst the GPU is still reading and writing to the VMA.
* Caveat emptor.
*
* Also note, that the object created here is not currently a "first class"
* object, in that several ioctls are banned. These are the CPU access
* ioctls: mmap(), pwrite and pread. In practice, you are expected to use
* direct access via your pointer rather than use those ioctls.
*
* If you think this is a good interface to use to pass GPU memory between
* drivers, please use dma-buf instead. In fact, wherever possible use
* dma-buf instead.
*/
int
i915_gem_userptr_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
{
struct drm_i915_private *dev_priv = dev->dev_private;
struct drm_i915_gem_userptr *args = data;
struct drm_i915_gem_object *obj;
int ret;
u32 handle;
if (args->flags & ~(I915_USERPTR_READ_ONLY |
I915_USERPTR_UNSYNCHRONIZED))
return -EINVAL;
if (offset_in_page(args->user_ptr | args->user_size))
return -EINVAL;
if (args->user_size > dev_priv->gtt.base.total)
return -E2BIG;
if (!access_ok(args->flags & I915_USERPTR_READ_ONLY ? VERIFY_READ : VERIFY_WRITE,
(char __user *)(unsigned long)args->user_ptr, args->user_size))
return -EFAULT;
if (args->flags & I915_USERPTR_READ_ONLY) {
/* On almost all of the current hw, we cannot tell the GPU that a
* page is readonly, so this is just a placeholder in the uAPI.
*/
return -ENODEV;
}
obj = i915_gem_object_alloc(dev);
if (obj == NULL)
return -ENOMEM;
drm_gem_private_object_init(dev, &obj->base, args->user_size);
i915_gem_object_init(obj, &i915_gem_userptr_ops);
obj->cache_level = I915_CACHE_LLC;
obj->base.write_domain = I915_GEM_DOMAIN_CPU;
obj->base.read_domains = I915_GEM_DOMAIN_CPU;
obj->userptr.ptr = args->user_ptr;
obj->userptr.read_only = !!(args->flags & I915_USERPTR_READ_ONLY);
/* And keep a pointer to the current->mm for resolving the user pages
* at binding. This means that we need to hook into the mmu_notifier
* in order to detect if the mmu is destroyed.
*/
ret = i915_gem_userptr_init__mm_struct(obj);
if (ret == 0)
ret = i915_gem_userptr_init__mmu_notifier(obj, args->flags);
if (ret == 0)
ret = drm_gem_handle_create(file, &obj->base, &handle);
/* drop reference from allocate - handle holds it now */
drm_gem_object_unreference_unlocked(&obj->base);
if (ret)
return ret;
args->handle = handle;
return 0;
}
int
i915_gem_init_userptr(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = to_i915(dev);
mutex_init(&dev_priv->mm_lock);
hash_init(dev_priv->mm_structs);
return 0;
}