drm/i915: Move more GEM objects under gem/

Continuing the theme of separating out the GEM clutter.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190528092956.14910-8-chris@chris-wilson.co.uk

1 files changed, 832 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
new file mode 100644
index 000000000000..ccac73b72597
--- /dev/null
+++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
@@ -0,0 +1,832 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2012-2014 Intel Corporation
+ */
+
+#include <linux/mmu_context.h>
+#include <linux/mmu_notifier.h>
+#include <linux/mempolicy.h>
+#include <linux/swap.h>
+#include <linux/sched/mm.h>
+
+#include <drm/i915_drm.h>
+
+#include "i915_gem_ioctls.h"
+#include "i915_gem_object.h"
+#include "i915_trace.h"
+#include "intel_drv.h"
+
+struct i915_mm_struct {
+	struct mm_struct *mm;
+	struct drm_i915_private *i915;
+	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_cached objects;
+	struct i915_mm_struct *mm;
+};
+
+struct i915_mmu_object {
+	struct i915_mmu_notifier *mn;
+	struct drm_i915_gem_object *obj;
+	struct interval_tree_node it;
+};
+
+static void add_object(struct i915_mmu_object *mo)
+{
+	GEM_BUG_ON(!RB_EMPTY_NODE(&mo->it.rb));
+	interval_tree_insert(&mo->it, &mo->mn->objects);
+}
+
+static void del_object(struct i915_mmu_object *mo)
+{
+	if (RB_EMPTY_NODE(&mo->it.rb))
+		return;
+
+	interval_tree_remove(&mo->it, &mo->mn->objects);
+	RB_CLEAR_NODE(&mo->it.rb);
+}
+
+static void
+__i915_gem_userptr_set_active(struct drm_i915_gem_object *obj, bool value)
+{
+	struct i915_mmu_object *mo = obj->userptr.mmu_object;
+
+	/*
+	 * During mm_invalidate_range we need to cancel any userptr that
+	 * overlaps the range being invalidated. Doing so requires the
+	 * struct_mutex, and that risks recursion. In order to cause
+	 * recursion, the user must alias the userptr address space with
+	 * a GTT mmapping (possible with a MAP_FIXED) - then when we have
+	 * to invalidate that mmaping, mm_invalidate_range is called with
+	 * the userptr address *and* the struct_mutex held.  To prevent that
+	 * we set a flag under the i915_mmu_notifier spinlock to indicate
+	 * whether this object is valid.
+	 */
+	if (!mo)
+		return;
+
+	spin_lock(&mo->mn->lock);
+	if (value)
+		add_object(mo);
+	else
+		del_object(mo);
+	spin_unlock(&mo->mn->lock);
+}
+
+static int
+userptr_mn_invalidate_range_start(struct mmu_notifier *_mn,
+				  const struct mmu_notifier_range *range)
+{
+	struct i915_mmu_notifier *mn =
+		container_of(_mn, struct i915_mmu_notifier, mn);
+	struct interval_tree_node *it;
+	struct mutex *unlock = NULL;
+	unsigned long end;
+	int ret = 0;
+
+	if (RB_EMPTY_ROOT(&mn->objects.rb_root))
+		return 0;
+
+	/* interval ranges are inclusive, but invalidate range is exclusive */
+	end = range->end - 1;
+
+	spin_lock(&mn->lock);
+	it = interval_tree_iter_first(&mn->objects, range->start, end);
+	while (it) {
+		struct drm_i915_gem_object *obj;
+
+		if (!mmu_notifier_range_blockable(range)) {
+			ret = -EAGAIN;
+			break;
+		}
+
+		/*
+		 * 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. To prevent that
+		 * use-after-free we only acquire a reference on the
+		 * object if it is not in the process of being destroyed.
+		 */
+		obj = container_of(it, struct i915_mmu_object, it)->obj;
+		if (!kref_get_unless_zero(&obj->base.refcount)) {
+			it = interval_tree_iter_next(it, range->start, end);
+			continue;
+		}
+		spin_unlock(&mn->lock);
+
+		if (!unlock) {
+			unlock = &mn->mm->i915->drm.struct_mutex;
+
+			switch (mutex_trylock_recursive(unlock)) {
+			default:
+			case MUTEX_TRYLOCK_FAILED:
+				if (mutex_lock_killable_nested(unlock, I915_MM_SHRINKER)) {
+					i915_gem_object_put(obj);
+					return -EINTR;
+				}
+				/* fall through */
+			case MUTEX_TRYLOCK_SUCCESS:
+				break;
+
+			case MUTEX_TRYLOCK_RECURSIVE:
+				unlock = ERR_PTR(-EEXIST);
+				break;
+			}
+		}
+
+		ret = i915_gem_object_unbind(obj);
+		if (ret == 0)
+			ret = __i915_gem_object_put_pages(obj, I915_MM_SHRINKER);
+		i915_gem_object_put(obj);
+		if (ret)
+			goto unlock;
+
+		spin_lock(&mn->lock);
+
+		/*
+		 * As we do not (yet) protect the mmu from concurrent insertion
+		 * over this range, there is no guarantee that this search will
+		 * terminate given a pathologic workload.
+		 */
+		it = interval_tree_iter_first(&mn->objects, range->start, end);
+	}
+	spin_unlock(&mn->lock);
+
+unlock:
+	if (!IS_ERR_OR_NULL(unlock))
+		mutex_unlock(unlock);
+
+	return ret;
+
+}
+
+static const struct mmu_notifier_ops i915_gem_userptr_notifier = {
+	.invalidate_range_start = userptr_mn_invalidate_range_start,
+};
+
+static struct i915_mmu_notifier *
+i915_mmu_notifier_create(struct i915_mm_struct *mm)
+{
+	struct i915_mmu_notifier *mn;
+
+	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_CACHED;
+	mn->mm = mm;
+
+	return mn;
+}
+
+static void
+i915_gem_userptr_release__mmu_notifier(struct drm_i915_gem_object *obj)
+{
+	struct i915_mmu_object *mo;
+
+	mo = fetch_and_zero(&obj->userptr.mmu_object);
+	if (!mo)
+		return;
+
+	spin_lock(&mo->mn->lock);
+	del_object(mo);
+	spin_unlock(&mo->mn->lock);
+	kfree(mo);
+}
+
+static struct i915_mmu_notifier *
+i915_mmu_notifier_find(struct i915_mm_struct *mm)
+{
+	struct i915_mmu_notifier *mn;
+	int err = 0;
+
+	mn = mm->mn;
+	if (mn)
+		return mn;
+
+	mn = i915_mmu_notifier_create(mm);
+	if (IS_ERR(mn))
+		err = PTR_ERR(mn);
+
+	down_write(&mm->mm->mmap_sem);
+	mutex_lock(&mm->i915->mm_lock);
+	if (mm->mn == NULL && !err) {
+		/* Protected by mmap_sem (write-lock) */
+		err = __mmu_notifier_register(&mn->mn, mm->mm);
+		if (!err) {
+			/* Protected by mm_lock */
+			mm->mn = fetch_and_zero(&mn);
+		}
+	} else if (mm->mn) {
+		/*
+		 * Someone else raced and successfully installed the mmu
+		 * notifier, we can cancel our own errors.
+		 */
+		err = 0;
+	}
+	mutex_unlock(&mm->i915->mm_lock);
+	up_write(&mm->mm->mmap_sem);
+
+	if (mn && !IS_ERR(mn))
+		kfree(mn);
+
+	return err ? ERR_PTR(err) : mm->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;
+
+	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)
+		return -ENOMEM;
+
+	mo->mn = mn;
+	mo->obj = obj;
+	mo->it.start = obj->userptr.ptr;
+	mo->it.last = obj->userptr.ptr + obj->base.size - 1;
+	RB_CLEAR_NODE(&mo->it.rb);
+
+	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_set_active(struct drm_i915_gem_object *obj, bool value)
+{
+}
+
+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->i915 = to_i915(obj->base.dev);
+
+		mm->mm = current->mm;
+		mmgrab(current->mm);
+
+		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(&mm->i915->mm_lock);
+
+	INIT_WORK(&mm->work, __i915_mm_struct_free__worker);
+	queue_work(mm->i915->mm.userptr_wq, &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;
+};
+
+static struct sg_table *
+__i915_gem_userptr_alloc_pages(struct drm_i915_gem_object *obj,
+			       struct page **pvec, int num_pages)
+{
+	unsigned int max_segment = i915_sg_segment_size();
+	struct sg_table *st;
+	unsigned int sg_page_sizes;
+	int ret;
+
+	st = kmalloc(sizeof(*st), GFP_KERNEL);
+	if (!st)
+		return ERR_PTR(-ENOMEM);
+
+alloc_table:
+	ret = __sg_alloc_table_from_pages(st, pvec, num_pages,
+					  0, num_pages << PAGE_SHIFT,
+					  max_segment,
+					  GFP_KERNEL);
+	if (ret) {
+		kfree(st);
+		return ERR_PTR(ret);
+	}
+
+	ret = i915_gem_gtt_prepare_pages(obj, st);
+	if (ret) {
+		sg_free_table(st);
+
+		if (max_segment > PAGE_SIZE) {
+			max_segment = PAGE_SIZE;
+			goto alloc_table;
+		}
+
+		kfree(st);
+		return ERR_PTR(ret);
+	}
+
+	sg_page_sizes = i915_sg_page_sizes(st->sgl);
+
+	__i915_gem_object_set_pages(obj, st, sg_page_sizes);
+
+	return st;
+}
+
+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;
+	const int npages = obj->base.size >> PAGE_SHIFT;
+	struct page **pvec;
+	int pinned, ret;
+
+	ret = -ENOMEM;
+	pinned = 0;
+
+	pvec = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
+	if (pvec != NULL) {
+		struct mm_struct *mm = obj->userptr.mm->mm;
+		unsigned int flags = 0;
+
+		if (!i915_gem_object_is_readonly(obj))
+			flags |= FOLL_WRITE;
+
+		ret = -EFAULT;
+		if (mmget_not_zero(mm)) {
+			down_read(&mm->mmap_sem);
+			while (pinned < npages) {
+				ret = get_user_pages_remote
+					(work->task, mm,
+					 obj->userptr.ptr + pinned * PAGE_SIZE,
+					 npages - pinned,
+					 flags,
+					 pvec + pinned, NULL, NULL);
+				if (ret < 0)
+					break;
+
+				pinned += ret;
+			}
+			up_read(&mm->mmap_sem);
+			mmput(mm);
+		}
+	}
+
+	mutex_lock(&obj->mm.lock);
+	if (obj->userptr.work == &work->work) {
+		struct sg_table *pages = ERR_PTR(ret);
+
+		if (pinned == npages) {
+			pages = __i915_gem_userptr_alloc_pages(obj, pvec,
+							       npages);
+			if (!IS_ERR(pages)) {
+				pinned = 0;
+				pages = NULL;
+			}
+		}
+
+		obj->userptr.work = ERR_CAST(pages);
+		if (IS_ERR(pages))
+			__i915_gem_userptr_set_active(obj, false);
+	}
+	mutex_unlock(&obj->mm.lock);
+
+	release_pages(pvec, pinned);
+	kvfree(pvec);
+
+	i915_gem_object_put(obj);
+	put_task_struct(work->task);
+	kfree(work);
+}
+
+static struct sg_table *
+__i915_gem_userptr_get_pages_schedule(struct drm_i915_gem_object *obj)
+{
+	struct get_pages_work *work;
+
+	/* 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.
+	 */
+	work = kmalloc(sizeof(*work), GFP_KERNEL);
+	if (work == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	obj->userptr.work = &work->work;
+
+	work->obj = i915_gem_object_get(obj);
+
+	work->task = current;
+	get_task_struct(work->task);
+
+	INIT_WORK(&work->work, __i915_gem_userptr_get_pages_worker);
+	queue_work(to_i915(obj->base.dev)->mm.userptr_wq, &work->work);
+
+	return ERR_PTR(-EAGAIN);
+}
+
+static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
+{
+	const int num_pages = obj->base.size >> PAGE_SHIFT;
+	struct mm_struct *mm = obj->userptr.mm->mm;
+	struct page **pvec;
+	struct sg_table *pages;
+	bool active;
+	int pinned;
+
+	/* 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.
+	 */
+
+	if (obj->userptr.work) {
+		/* active flag should still be held for the pending work */
+		if (IS_ERR(obj->userptr.work))
+			return PTR_ERR(obj->userptr.work);
+		else
+			return -EAGAIN;
+	}
+
+	pvec = NULL;
+	pinned = 0;
+
+	if (mm == current->mm) {
+		pvec = kvmalloc_array(num_pages, sizeof(struct page *),
+				      GFP_KERNEL |
+				      __GFP_NORETRY |
+				      __GFP_NOWARN);
+		if (pvec) /* defer to worker if malloc fails */
+			pinned = __get_user_pages_fast(obj->userptr.ptr,
+						       num_pages,
+						       !i915_gem_object_is_readonly(obj),
+						       pvec);
+	}
+
+	active = false;
+	if (pinned < 0) {
+		pages = ERR_PTR(pinned);
+		pinned = 0;
+	} else if (pinned < num_pages) {
+		pages = __i915_gem_userptr_get_pages_schedule(obj);
+		active = pages == ERR_PTR(-EAGAIN);
+	} else {
+		pages = __i915_gem_userptr_alloc_pages(obj, pvec, num_pages);
+		active = !IS_ERR(pages);
+	}
+	if (active)
+		__i915_gem_userptr_set_active(obj, true);
+
+	if (IS_ERR(pages))
+		release_pages(pvec, pinned);
+	kvfree(pvec);
+
+	return PTR_ERR_OR_ZERO(pages);
+}
+
+static void
+i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj,
+			   struct sg_table *pages)
+{
+	struct sgt_iter sgt_iter;
+	struct page *page;
+
+	/* Cancel any inflight work and force them to restart their gup */
+	obj->userptr.work = NULL;
+	__i915_gem_userptr_set_active(obj, false);
+	if (!pages)
+		return;
+
+	__i915_gem_object_release_shmem(obj, pages, true);
+	i915_gem_gtt_finish_pages(obj, pages);
+
+	for_each_sgt_page(page, sgt_iter, pages) {
+		if (obj->mm.dirty)
+			set_page_dirty(page);
+
+		mark_page_accessed(page);
+		put_page(page);
+	}
+	obj->mm.dirty = false;
+
+	sg_free_table(pages);
+	kfree(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 = {
+	.flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE |
+		 I915_GEM_OBJECT_IS_SHRINKABLE |
+		 I915_GEM_OBJECT_ASYNC_CANCEL,
+	.get_pages = i915_gem_userptr_get_pages,
+	.put_pages = i915_gem_userptr_put_pages,
+	.dmabuf_export = i915_gem_userptr_dmabuf_export,
+	.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. Another
+ * restriction is that we do not allow userptr surfaces to be pinned to the
+ * hardware and so we reject any attempt to create a framebuffer out of a
+ * userptr.
+ *
+ * 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 = to_i915(dev);
+	struct drm_i915_gem_userptr *args = data;
+	struct drm_i915_gem_object *obj;
+	int ret;
+	u32 handle;
+
+	if (!HAS_LLC(dev_priv) && !HAS_SNOOP(dev_priv)) {
+		/* We cannot support coherent userptr objects on hw without
+		 * LLC and broken snooping.
+		 */
+		return -ENODEV;
+	}
+
+	if (args->flags & ~(I915_USERPTR_READ_ONLY |
+			    I915_USERPTR_UNSYNCHRONIZED))
+		return -EINVAL;
+
+	if (!args->user_size)
+		return -EINVAL;
+
+	if (offset_in_page(args->user_ptr | args->user_size))
+		return -EINVAL;
+
+	if (!access_ok((char __user *)(unsigned long)args->user_ptr, args->user_size))
+		return -EFAULT;
+
+	if (args->flags & I915_USERPTR_READ_ONLY) {
+		struct i915_hw_ppgtt *ppgtt;
+
+		/*
+		 * On almost all of the older hw, we cannot tell the GPU that
+		 * a page is readonly.
+		 */
+		ppgtt = dev_priv->kernel_context->ppgtt;
+		if (!ppgtt || !ppgtt->vm.has_read_only)
+			return -ENODEV;
+	}
+
+	obj = i915_gem_object_alloc();
+	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->read_domains = I915_GEM_DOMAIN_CPU;
+	obj->write_domain = I915_GEM_DOMAIN_CPU;
+	i915_gem_object_set_cache_coherency(obj, I915_CACHE_LLC);
+
+	obj->userptr.ptr = args->user_ptr;
+	if (args->flags & I915_USERPTR_READ_ONLY)
+		i915_gem_object_set_readonly(obj);
+
+	/* 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 */
+	i915_gem_object_put(obj);
+	if (ret)
+		return ret;
+
+	args->handle = handle;
+	return 0;
+}
+
+int i915_gem_init_userptr(struct drm_i915_private *dev_priv)
+{
+	mutex_init(&dev_priv->mm_lock);
+	hash_init(dev_priv->mm_structs);
+
+	dev_priv->mm.userptr_wq =
+		alloc_workqueue("i915-userptr-acquire",
+				WQ_HIGHPRI | WQ_UNBOUND,
+				0);
+	if (!dev_priv->mm.userptr_wq)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void i915_gem_cleanup_userptr(struct drm_i915_private *dev_priv)
+{
+	destroy_workqueue(dev_priv->mm.userptr_wq);
+}