drivers/gpu/drm/i915/i915_gem_execbuffer.c

/*
 * Copyright © 2008,2010 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.
 *
 * Authors:
 *    Eric Anholt <eric@anholt.net>
 *    Chris Wilson <chris@chris-wilson.co.uk>
 *
 */

#include <drm/drmP.h>
#include <drm/i915_drm.h>
#include "i915_drv.h"
#include "i915_trace.h"
#include "intel_drv.h"
#include <linux/dma_remapping.h>

#define  __EXEC_OBJECT_HAS_PIN (1<<31)
#define  __EXEC_OBJECT_HAS_FENCE (1<<30)
#define  __EXEC_OBJECT_NEEDS_MAP (1<<29)
#define  __EXEC_OBJECT_NEEDS_BIAS (1<<28)

#define BATCH_OFFSET_BIAS (256*1024)

struct eb_vmas {
	struct list_head vmas;
	int and;
	union {
		struct i915_vma *lut[0];
		struct hlist_head buckets[0];
	};
};

static struct eb_vmas *
eb_create(struct drm_i915_gem_execbuffer2 *args)
{
	struct eb_vmas *eb = NULL;

	if (args->flags & I915_EXEC_HANDLE_LUT) {
		unsigned size = args->buffer_count;
		size *= sizeof(struct i915_vma *);
		size += sizeof(struct eb_vmas);
		eb = kmalloc(size, GFP_TEMPORARY | __GFP_NOWARN | __GFP_NORETRY);
	}

	if (eb == NULL) {
		unsigned size = args->buffer_count;
		unsigned count = PAGE_SIZE / sizeof(struct hlist_head) / 2;
		BUILD_BUG_ON_NOT_POWER_OF_2(PAGE_SIZE / sizeof(struct hlist_head));
		while (count > 2*size)
			count >>= 1;
		eb = kzalloc(count*sizeof(struct hlist_head) +
			     sizeof(struct eb_vmas),
			     GFP_TEMPORARY);
		if (eb == NULL)
			return eb;

		eb->and = count - 1;
	} else
		eb->and = -args->buffer_count;

	INIT_LIST_HEAD(&eb->vmas);
	return eb;
}

static void
eb_reset(struct eb_vmas *eb)
{
	if (eb->and >= 0)
		memset(eb->buckets, 0, (eb->and+1)*sizeof(struct hlist_head));
}

static int
eb_lookup_vmas(struct eb_vmas *eb,
	       struct drm_i915_gem_exec_object2 *exec,
	       const struct drm_i915_gem_execbuffer2 *args,
	       struct i915_address_space *vm,
	       struct drm_file *file)
{
	struct drm_i915_private *dev_priv = vm->dev->dev_private;
	struct drm_i915_gem_object *obj;
	struct list_head objects;
	int i, ret;

	INIT_LIST_HEAD(&objects);
	spin_lock(&file->table_lock);
	/* Grab a reference to the object and release the lock so we can lookup
	 * or create the VMA without using GFP_ATOMIC */
	for (i = 0; i < args->buffer_count; i++) {
		obj = to_intel_bo(idr_find(&file->object_idr, exec[i].handle));
		if (obj == NULL) {
			spin_unlock(&file->table_lock);
			DRM_DEBUG("Invalid object handle %d at index %d\n",
				   exec[i].handle, i);
			ret = -ENOENT;
			goto err;
		}

		if (!list_empty(&obj->obj_exec_link)) {
			spin_unlock(&file->table_lock);
			DRM_DEBUG("Object %p [handle %d, index %d] appears more than once in object list\n",
				   obj, exec[i].handle, i);
			ret = -EINVAL;
			goto err;
		}

		drm_gem_object_reference(&obj->base);
		list_add_tail(&obj->obj_exec_link, &objects);
	}
	spin_unlock(&file->table_lock);

	i = 0;
	while (!list_empty(&objects)) {
		struct i915_vma *vma;
		struct i915_address_space *bind_vm = vm;

		if (exec[i].flags & EXEC_OBJECT_NEEDS_GTT &&
		    USES_FULL_PPGTT(vm->dev)) {
			ret = -EINVAL;
			goto err;
		}

		/* If we have secure dispatch, or the userspace assures us that
		 * they know what they're doing, use the GGTT VM.
		 */
		if (((args->flags & I915_EXEC_SECURE) &&
		    (i == (args->buffer_count - 1))))
			bind_vm = &dev_priv->gtt.base;

		obj = list_first_entry(&objects,
				       struct drm_i915_gem_object,
				       obj_exec_link);

		/*
		 * NOTE: We can leak any vmas created here when something fails
		 * later on. But that's no issue since vma_unbind can deal with
		 * vmas which are not actually bound. And since only
		 * lookup_or_create exists as an interface to get at the vma
		 * from the (obj, vm) we don't run the risk of creating
		 * duplicated vmas for the same vm.
		 */
		vma = i915_gem_obj_lookup_or_create_vma(obj, bind_vm);
		if (IS_ERR(vma)) {
			DRM_DEBUG("Failed to lookup VMA\n");
			ret = PTR_ERR(vma);
			goto err;
		}

		/* Transfer ownership from the objects list to the vmas list. */
		list_add_tail(&vma->exec_list, &eb->vmas);
		list_del_init(&obj->obj_exec_link);

		vma->exec_entry = &exec[i];
		if (eb->and < 0) {
			eb->lut[i] = vma;
		} else {
			uint32_t handle = args->flags & I915_EXEC_HANDLE_LUT ? i : exec[i].handle;
			vma->exec_handle = handle;
			hlist_add_head(&vma->exec_node,
				       &eb->buckets[handle & eb->and]);
		}
		++i;
	}

	return 0;


err:
	while (!list_empty(&objects)) {
		obj = list_first_entry(&objects,
				       struct drm_i915_gem_object,
				       obj_exec_link);
		list_del_init(&obj->obj_exec_link);
		drm_gem_object_unreference(&obj->base);
	}
	/*
	 * Objects already transfered to the vmas list will be unreferenced by
	 * eb_destroy.
	 */

	return ret;
}

static struct i915_vma *eb_get_vma(struct eb_vmas *eb, unsigned long handle)
{
	if (eb->and < 0) {
		if (handle >= -eb->and)
			return NULL;
		return eb->lut[handle];
	} else {
		struct hlist_head *head;
		struct hlist_node *node;

		head = &eb->buckets[handle & eb->and];
		hlist_for_each(node, head) {
			struct i915_vma *vma;

			vma = hlist_entry(node, struct i915_vma, exec_node);
			if (vma->exec_handle == handle)
				return vma;
		}
		return NULL;
	}
}

static void
i915_gem_execbuffer_unreserve_vma(struct i915_vma *vma)
{
	struct drm_i915_gem_exec_object2 *entry;
	struct drm_i915_gem_object *obj = vma->obj;

	if (!drm_mm_node_allocated(&vma->node))
		return;

	entry = vma->exec_entry;

	if (entry->flags & __EXEC_OBJECT_HAS_FENCE)
		i915_gem_object_unpin_fence(obj);

	if (entry->flags & __EXEC_OBJECT_HAS_PIN)
		vma->pin_count--;

	entry->flags &= ~(__EXEC_OBJECT_HAS_FENCE | __EXEC_OBJECT_HAS_PIN);
}

static void eb_destroy(struct eb_vmas *eb)
{
	while (!list_empty(&eb->vmas)) {
		struct i915_vma *vma;

		vma = list_first_entry(&eb->vmas,
				       struct i915_vma,
				       exec_list);
		list_del_init(&vma->exec_list);
		i915_gem_execbuffer_unreserve_vma(vma);
		drm_gem_object_unreference(&vma->obj->base);
	}
	kfree(eb);
}

static inline int use_cpu_reloc(struct drm_i915_gem_object *obj)
{
	return (HAS_LLC(obj->base.dev) ||
		obj->base.write_domain == I915_GEM_DOMAIN_CPU ||
		!obj->map_and_fenceable ||
		obj->cache_level != I915_CACHE_NONE);
}

static int
relocate_entry_cpu(struct drm_i915_gem_object *obj,
		   struct drm_i915_gem_relocation_entry *reloc,
		   uint64_t target_offset)
{
	struct drm_device *dev = obj->base.dev;
	uint32_t page_offset = offset_in_page(reloc->offset);
	uint64_t delta = reloc->delta + target_offset;
	char *vaddr;
	int ret;

	ret = i915_gem_object_set_to_cpu_domain(obj, true);
	if (ret)
		return ret;

	vaddr = kmap_atomic(i915_gem_object_get_page(obj,
				reloc->offset >> PAGE_SHIFT));
	*(uint32_t *)(vaddr + page_offset) = lower_32_bits(delta);

	if (INTEL_INFO(dev)->gen >= 8) {
		page_offset = offset_in_page(page_offset + sizeof(uint32_t));

		if (page_offset == 0) {
			kunmap_atomic(vaddr);
			vaddr = kmap_atomic(i915_gem_object_get_page(obj,
			    (reloc->offset + sizeof(uint32_t)) >> PAGE_SHIFT));
		}

		*(uint32_t *)(vaddr + page_offset) = upper_32_bits(delta);
	}

	kunmap_atomic(vaddr);

	return 0;
}

static int
relocate_entry_gtt(struct drm_i915_gem_object *obj,
		   struct drm_i915_gem_relocation_entry *reloc,
		   uint64_t target_offset)
{
	struct drm_device *dev = obj->base.dev;
	struct drm_i915_private *dev_priv = dev->dev_private;
	uint64_t delta = reloc->delta + target_offset;
	uint32_t __iomem *reloc_entry;
	void __iomem *reloc_page;
	int ret;

	ret = i915_gem_object_set_to_gtt_domain(obj, true);
	if (ret)
		return ret;

	ret = i915_gem_object_put_fence(obj);
	if (ret)
		return ret;

	/* Map the page containing the relocation we're going to perform.  */
	reloc->offset += i915_gem_obj_ggtt_offset(obj);
	reloc_page = io_mapping_map_atomic_wc(dev_priv->gtt.mappable,
			reloc->offset & PAGE_MASK);
	reloc_entry = (uint32_t __iomem *)
		(reloc_page + offset_in_page(reloc->offset));
	iowrite32(lower_32_bits(delta), reloc_entry);

	if (INTEL_INFO(dev)->gen >= 8) {
		reloc_entry += 1;

		if (offset_in_page(reloc->offset + sizeof(uint32_t)) == 0) {
			io_mapping_unmap_atomic(reloc_page);
			reloc_page = io_mapping_map_atomic_wc(
					dev_priv->gtt.mappable,
					reloc->offset + sizeof(uint32_t));
			reloc_entry = reloc_page;
		}

		iowrite32(upper_32_bits(delta), reloc_entry);
	}

	io_mapping_unmap_atomic(reloc_page);

	return 0;
}

static int
i915_gem_execbuffer_relocate_entry(struct drm_i915_gem_object *obj,
				   struct eb_vmas *eb,
				   struct drm_i915_gem_relocation_entry *reloc)
{
	struct drm_device *dev = obj->base.dev;
	struct drm_gem_object *target_obj;
	struct drm_i915_gem_object *target_i915_obj;
	struct i915_vma *target_vma;
	uint64_t target_offset;
	int ret;

	/* we've already hold a reference to all valid objects */
	target_vma = eb_get_vma(eb, reloc->target_handle);
	if (unlikely(target_vma == NULL))
		return -ENOENT;
	target_i915_obj = target_vma->obj;
	target_obj = &target_vma->obj->base;

	target_offset = target_vma->node.start;

	/* Sandybridge PPGTT errata: We need a global gtt mapping for MI and
	 * pipe_control writes because the gpu doesn't properly redirect them
	 * through the ppgtt for non_secure batchbuffers. */
	if (unlikely(IS_GEN6(dev) &&
	    reloc->write_domain == I915_GEM_DOMAIN_INSTRUCTION &&
	    !target_i915_obj->has_global_gtt_mapping)) {
		struct i915_vma *vma =
			list_first_entry(&target_i915_obj->vma_list,
					 typeof(*vma), vma_link);
		vma->bind_vma(vma, target_i915_obj->cache_level, GLOBAL_BIND);
	}

	/* Validate that the target is in a valid r/w GPU domain */
	if (unlikely(reloc->write_domain & (reloc->write_domain - 1))) {
		DRM_DEBUG("reloc with multiple write domains: "
			  "obj %p target %d offset %d "
			  "read %08x write %08x",
			  obj, reloc->target_handle,
			  (int) reloc->offset,
			  reloc->read_domains,
			  reloc->write_domain);
		return -EINVAL;
	}
	if (unlikely((reloc->write_domain | reloc->read_domains)
		     & ~I915_GEM_GPU_DOMAINS)) {
		DRM_DEBUG("reloc with read/write non-GPU domains: "
			  "obj %p target %d offset %d "
			  "read %08x write %08x",
			  obj, reloc->target_handle,
			  (int) reloc->offset,
			  reloc->read_domains,
			  reloc->write_domain);
		return -EINVAL;
	}

	target_obj->pending_read_domains |= reloc->read_domains;
	target_obj->pending_write_domain |= reloc->write_domain;

	/* If the relocation already has the right value in it, no
	 * more work needs to be done.
	 */
	if (target_offset == reloc->presumed_offset)
		return 0;

	/* Check that the relocation address is valid... */
	if (unlikely(reloc->offset >
		obj->base.size - (INTEL_INFO(dev)->gen >= 8 ? 8 : 4))) {
		DRM_DEBUG("Relocation beyond object bounds: "
			  "obj %p target %d offset %d size %d.\n",
			  obj, reloc->target_handle,
			  (int) reloc->offset,
			  (int) obj->base.size);
		return -EINVAL;
	}
	if (unlikely(reloc->offset & 3)) {
		DRM_DEBUG("Relocation not 4-byte aligned: "
			  "obj %p target %d offset %d.\n",
			  obj, reloc->target_handle,
			  (int) reloc->offset);
		return -EINVAL;
	}

	/* We can't wait for rendering with pagefaults disabled */
	if (obj->active && in_atomic())
		return -EFAULT;

	if (use_cpu_reloc(obj))
		ret = relocate_entry_cpu(obj, reloc, target_offset);
	else
		ret = relocate_entry_gtt(obj, reloc, target_offset);

	if (ret)
		return ret;

	/* and update the user's relocation entry */
	reloc->presumed_offset = target_offset;

	return 0;
}

static int
i915_gem_execbuffer_relocate_vma(struct i915_vma *vma,
				 struct eb_vmas *eb)
{
#define N_RELOC(x) ((x) / sizeof(struct drm_i915_gem_relocation_entry))
	struct drm_i915_gem_relocation_entry stack_reloc[N_RELOC(512)];
	struct drm_i915_gem_relocation_entry __user *user_relocs;
	struct drm_i915_gem_exec_object2 *entry = vma->exec_entry;
	int remain, ret;

	user_relocs = to_user_ptr(entry->relocs_ptr);

	remain = entry->relocation_count;
	while (remain) {
		struct drm_i915_gem_relocation_entry *r = stack_reloc;
		int count = remain;
		if (count > ARRAY_SIZE(stack_reloc))
			count = ARRAY_SIZE(stack_reloc);
		remain -= count;

		if (__copy_from_user_inatomic(r, user_relocs, count*sizeof(r[0])))
			return -EFAULT;

		do {
			u64 offset = r->presumed_offset;

			ret = i915_gem_execbuffer_relocate_entry(vma->obj, eb, r);
			if (ret)
				return ret;

			if (r->presumed_offset != offset &&
			    __copy_to_user_inatomic(&user_relocs->presumed_offset,
						    &r->presumed_offset,
						    sizeof(r->presumed_offset))) {
				return -EFAULT;
			}

			user_relocs++;
			r++;
		} while (--count);
	}

	return 0;
#undef N_RELOC
}

static int
i915_gem_execbuffer_relocate_vma_slow(struct i915_vma *vma,
				      struct eb_vmas *eb,
				      struct drm_i915_gem_relocation_entry *relocs)
{
	const struct drm_i915_gem_exec_object2 *entry = vma->exec_entry;
	int i, ret;

	for (i = 0; i < entry->relocation_count; i++) {
		ret = i915_gem_execbuffer_relocate_entry(vma->obj, eb, &relocs[i]);
		if (ret)
			return ret;
	}

	return 0;
}

static int
i915_gem_execbuffer_relocate(struct eb_vmas *eb)
{
	struct i915_vma *vma;
	int ret = 0;

	/* This is the fast path and we cannot handle a pagefault whilst
	 * holding the struct mutex lest the user pass in the relocations
	 * contained within a mmaped bo. For in such a case we, the page
	 * fault handler would call i915_gem_fault() and we would try to
	 * acquire the struct mutex again. Obviously this is bad and so
	 * lockdep complains vehemently.
	 */
	pagefault_disable();
	list_for_each_entry(vma, &eb->vmas, exec_list) {
		ret = i915_gem_execbuffer_relocate_vma(vma, eb);
		if (ret)
			break;
	}
	pagefault_enable();

	return ret;
}

static int
i915_gem_execbuffer_reserve_vma(struct i915_vma *vma,
				struct intel_engine_cs *ring,
				bool *need_reloc)
{
	struct drm_i915_gem_object *obj = vma->obj;
	struct drm_i915_gem_exec_object2 *entry = vma->exec_entry;
	uint64_t flags;
	int ret;

	flags = 0;
	if (entry->flags & __EXEC_OBJECT_NEEDS_MAP)
		flags |= PIN_MAPPABLE;
	if (entry->flags & EXEC_OBJECT_NEEDS_GTT)
		flags |= PIN_GLOBAL;
	if (entry->flags & __EXEC_OBJECT_NEEDS_BIAS)
		flags |= BATCH_OFFSET_BIAS | PIN_OFFSET_BIAS;

	ret = i915_gem_object_pin(obj, vma->vm, entry->alignment, flags);
	if (ret)
		return ret;

	entry->flags |= __EXEC_OBJECT_HAS_PIN;

	if (entry->flags & EXEC_OBJECT_NEEDS_FENCE) {
		ret = i915_gem_object_get_fence(obj);
		if (ret)
			return ret;

		if (i915_gem_object_pin_fence(obj))
			entry->flags |= __EXEC_OBJECT_HAS_FENCE;
	}

	if (entry->offset != vma->node.start) {
		entry->offset = vma->node.start;
		*need_reloc = true;
	}

	if (entry->flags & EXEC_OBJECT_WRITE) {
		obj->base.pending_read_domains = I915_GEM_DOMAIN_RENDER;
		obj->base.pending_write_domain = I915_GEM_DOMAIN_RENDER;
	}

	return 0;
}

static bool
need_reloc_mappable(struct i915_vma *vma)
{
	struct drm_i915_gem_exec_object2 *entry = vma->exec_entry;

	if (entry->relocation_count == 0)
		return false;

	if (!i915_is_ggtt(vma->vm))
		return false;

	/* See also use_cpu_reloc() */
	if (HAS_LLC(vma->obj->base.dev))
		return false;

	if (vma->obj->base.write_domain == I915_GEM_DOMAIN_CPU)
		return false;

	return true;
}

static bool
eb_vma_misplaced(struct i915_vma *vma)
{
	struct drm_i915_gem_exec_object2 *entry = vma->exec_entry;
	struct drm_i915_gem_object *obj = vma->obj;

	WARN_ON(entry->flags & __EXEC_OBJECT_NEEDS_MAP &&
	       !i915_is_ggtt(vma->vm));

	if (entry->alignment &&
	    vma->node.start & (entry->alignment - 1))
		return true;

	if (entry->flags & __EXEC_OBJECT_NEEDS_MAP && !obj->map_and_fenceable)
		return true;

	if (entry->flags & __EXEC_OBJECT_NEEDS_BIAS &&
	    vma->node.start < BATCH_OFFSET_BIAS)
		return true;

	return false;
}

static int
i915_gem_execbuffer_reserve(struct intel_engine_cs *ring,
			    struct list_head *vmas,
			    bool *need_relocs)
{
	struct drm_i915_gem_object *obj;
	struct i915_vma *vma;
	struct i915_address_space *vm;
	struct list_head ordered_vmas;
	bool has_fenced_gpu_access = INTEL_INFO(ring->dev)->gen < 4;
	int retry;

	if (list_empty(vmas))
		return 0;

	i915_gem_retire_requests_ring(ring);

	vm = list_first_entry(vmas, struct i915_vma, exec_list)->vm;

	INIT_LIST_HEAD(&ordered_vmas);
	while (!list_empty(vmas)) {
		struct drm_i915_gem_exec_object2 *entry;
		bool need_fence, need_mappable;

		vma = list_first_entry(vmas, struct i915_vma, exec_list);
		obj = vma->obj;
		entry = vma->exec_entry;

		if (!has_fenced_gpu_access)
			entry->flags &= ~EXEC_OBJECT_NEEDS_FENCE;
		need_fence =
			entry->flags & EXEC_OBJECT_NEEDS_FENCE &&
			obj->tiling_mode != I915_TILING_NONE;
		need_mappable = need_fence || need_reloc_mappable(vma);

		if (need_mappable) {
			entry->flags |= __EXEC_OBJECT_NEEDS_MAP;
			list_move(&vma->exec_list, &ordered_vmas);
		} else
			list_move_tail(&vma->exec_list, &ordered_vmas);

		obj->base.pending_read_domains = I915_GEM_GPU_DOMAINS & ~I915_GEM_DOMAIN_COMMAND;
		obj->base.pending_write_domain = 0;
	}
	list_splice(&ordered_vmas, vmas);

	/* Attempt to pin all of the buffers into the GTT.
	 * This is done in 3 phases:
	 *
	 * 1a. Unbind all objects that do not match the GTT constraints for
	 *     the execbuffer (fenceable, mappable, alignment etc).
	 * 1b. Increment pin count for already bound objects.
	 * 2.  Bind new objects.
	 * 3.  Decrement pin count.
	 *
	 * This avoid unnecessary unbinding of later objects in order to make
	 * room for the earlier objects *unless* we need to defragment.
	 */
	retry = 0;
	do {
		int ret = 0;

		/* Unbind any ill-fitting objects or pin. */
		list_for_each_entry(vma, vmas, exec_list) {
			if (!drm_mm_node_allocated(&vma->node))
				continue;

			if (eb_vma_misplaced(vma))
				ret = i915_vma_unbind(vma);
			else
				ret = i915_gem_execbuffer_reserve_vma(vma, ring, need_relocs);
			if (ret)
				goto err;
		}

		/* Bind fresh objects */
		list_for_each_entry(vma, vmas, exec_list) {
			if (drm_mm_node_allocated(&vma->node))
				continue;

			ret = i915_gem_execbuffer_reserve_vma(vma, ring, need_relocs);
			if (ret)
				goto err;
		}

err:
		if (ret != -ENOSPC || retry++)
			return ret;

		/* Decrement pin count for bound objects */
		list_for_each_entry(vma, vmas, exec_list)
			i915_gem_execbuffer_unreserve_vma(vma);

		ret = i915_gem_evict_vm(vm, true);
		if (ret)
			return ret;
	} while (1);
}

static int
i915_gem_execbuffer_relocate_slow(struct drm_device *dev,
				  struct drm_i915_gem_execbuffer2 *args,
				  struct drm_file *file,
				  struct intel_engine_cs *ring,
				  struct eb_vmas *eb,
				  struct drm_i915_gem_exec_object2 *exec)
{
	struct drm_i915_gem_relocation_entry *reloc;
	struct i915_address_space *vm;
	struct i915_vma *vma;
	bool need_relocs;
	int *reloc_offset;
	int i, total, ret;
	unsigned count = args->buffer_count;

	if (WARN_ON(list_empty(&eb->vmas)))
		return 0;

	vm = list_first_entry(&eb->vmas, struct i915_vma, exec_list)->vm;

	/* We may process another execbuffer during the unlock... */
	while (!list_empty(&eb->vmas)) {
		vma = list_first_entry(&eb->vmas, struct i915_vma, exec_list);
		list_del_init(&vma->exec_list);
		i915_gem_execbuffer_unreserve_vma(vma);
		drm_gem_object_unreference(&vma->obj->base);
	}

	mutex_unlock(&dev->struct_mutex);

	total = 0;
	for (i = 0; i < count; i++)
		total += exec[i].relocation_count;

	reloc_offset = drm_malloc_ab(count, sizeof(*reloc_offset));
	reloc = drm_malloc_ab(total, sizeof(*reloc));
	if (reloc == NULL || reloc_offset == NULL) {
		drm_free_large(reloc);
		drm_free_large(reloc_offset);
		mutex_lock(&dev->struct_mutex);
		return -ENOMEM;
	}

	total = 0;
	for (i = 0; i < count; i++) {
		struct drm_i915_gem_relocation_entry __user *user_relocs;
		u64 invalid_offset = (u64)-1;
		int j;

		user_relocs = to_user_ptr(exec[i].relocs_ptr);

		if (copy_from_user(reloc+total, user_relocs,
				   exec[i].relocation_count * sizeof(*reloc))) {
			ret = -EFAULT;
			mutex_lock(&dev->struct_mutex);
			goto err;
		}

		/* As we do not update the known relocation offsets after
		 * relocating (due to the complexities in lock handling),
		 * we need to mark them as invalid now so that we force the
		 * relocation processing next time. Just in case the target
		 * object is evicted and then rebound into its old
		 * presumed_offset before the next execbuffer - if that
		 * happened we would make the mistake of assuming that the
		 * relocations were valid.
		 */
		for (j = 0; j < exec[i].relocation_count; j++) {
			if (__copy_to_user(&user_relocs[j].presumed_offset,
					   &invalid_offset,
					   sizeof(invalid_offset))) {
				ret = -EFAULT;
				mutex_lock(&dev->struct_mutex);
				goto err;
			}
		}

		reloc_offset[i] = total;
		total += exec[i].relocation_count;
	}

	ret = i915_mutex_lock_interruptible(dev);
	if (ret) {
		mutex_lock(&dev->struct_mutex);
		goto err;
	}

	/* reacquire the objects */
	eb_reset(eb);
	ret = eb_lookup_vmas(eb, exec, args, vm, file);
	if (ret)
		goto err;

	need_relocs = (args->flags & I915_EXEC_NO_RELOC) == 0;
	ret = i915_gem_execbuffer_reserve(ring, &eb->vmas, &need_relocs);
	if (ret)
		goto err;

	list_for_each_entry(vma, &eb->vmas, exec_list) {
		int offset = vma->exec_entry - exec;
		ret = i915_gem_execbuffer_relocate_vma_slow(vma, eb,
							    reloc + reloc_offset[offset]);
		if (ret)
			goto err;
	}

	/* Leave the user relocations as are, this is the painfully slow path,
	 * and we want to avoid the complication of dropping the lock whilst
	 * having buffers reserved in the aperture and so causing spurious
	 * ENOSPC for random operations.
	 */

err:
	drm_free_large(reloc);
	drm_free_large(reloc_offset);
	return ret;
}

static int
i915_gem_execbuffer_move_to_gpu(struct intel_engine_cs *ring,
				struct list_head *vmas)
{
	struct i915_vma *vma;
	uint32_t flush_domains = 0;
	bool flush_chipset = false;
	int ret;

	list_for_each_entry(vma, vmas, exec_list) {
		struct drm_i915_gem_object *obj = vma->obj;
		ret = i915_gem_object_sync(obj, ring);
		if (ret)
			return ret;

		if (obj->base.write_domain & I915_GEM_DOMAIN_CPU)
			flush_chipset |= i915_gem_clflush_object(obj, false);

		flush_domains |= obj->base.write_domain;
	}

	if (flush_chipset)
		i915_gem_chipset_flush(ring->dev);

	if (flush_domains & I915_GEM_DOMAIN_GTT)
		wmb();

	/* Unconditionally invalidate gpu caches and ensure that we do flush
	 * any residual writes from the previous batch.
	 */
	return intel_ring_invalidate_all_caches(ring);
}

static bool
i915_gem_check_execbuffer(struct drm_i915_gem_execbuffer2 *exec)
{
	if (exec->flags & __I915_EXEC_UNKNOWN_FLAGS)
		return false;

	return ((exec->batch_start_offset | exec->batch_len) & 0x7) == 0;
}

static int
validate_exec_list(struct drm_i915_gem_exec_object2 *exec,
		   int count)
{
	int i;
	unsigned relocs_total = 0;
	unsigned relocs_max = UINT_MAX / sizeof(struct drm_i915_gem_relocation_entry);

	for (i = 0; i < count; i++) {
		char __user *ptr = to_user_ptr(exec[i].relocs_ptr);
		int length; /* limited by fault_in_pages_readable() */

		if (exec[i].flags & __EXEC_OBJECT_UNKNOWN_FLAGS)
			return -EINVAL;

		/* First check for malicious input causing overflow in
		 * the worst case where we need to allocate the entire
		 * relocation tree as a single array.
		 */
		if (exec[i].relocation_count > relocs_max - relocs_total)
			return -EINVAL;
		relocs_total += exec[i].relocation_count;

		length = exec[i].relocation_count *
			sizeof(struct drm_i915_gem_relocation_entry);
		/*
		 * We must check that the entire relocation array is safe
		 * to read, but since we may need to update the presumed
		 * offsets during execution, check for full write access.
		 */
		if (!access_ok(VERIFY_WRITE, ptr, length))
			return -EFAULT;

		if (likely(!i915.prefault_disable)) {
			if (fault_in_multipages_readable(ptr, length))
				return -EFAULT;
		}
	}

	return 0;
}

static struct intel_context *
i915_gem_validate_context(struct drm_device *dev, struct drm_file *file,
			  struct intel_engine_cs *ring, const u32 ctx_id)
{
	struct intel_context *ctx = NULL;
	struct i915_ctx_hang_stats *hs;

	if (ring->id != RCS && ctx_id != DEFAULT_CONTEXT_HANDLE)
		return ERR_PTR(-EINVAL);

	ctx = i915_gem_context_get(file->driver_priv, ctx_id);
	if (IS_ERR(ctx))
		return ctx;

	hs = &ctx->hang_stats;
	if (hs->banned) {
		DRM_DEBUG("Context %u tried to submit while banned\n", ctx_id);
		return ERR_PTR(-EIO);
	}

	return ctx;
}

static void
i915_gem_execbuffer_move_to_active(struct list_head *vmas,
				   struct intel_engine_cs *ring)
{
	u32 seqno = intel_ring_get_seqno(ring);
	struct i915_vma *vma;

	list_for_each_entry(vma, vmas, exec_list) {
		struct drm_i915_gem_exec_object2 *entry = vma->exec_entry;
		struct drm_i915_gem_object *obj = vma->obj;
		u32 old_read = obj->base.read_domains;
		u32 old_write = obj->base.write_domain;

		obj->base.write_domain = obj->base.pending_write_domain;
		if (obj->base.write_domain == 0)
			obj->base.pending_read_domains |= obj->base.read_domains;
		obj->base.read_domains = obj->base.pending_read_domains;

		i915_vma_move_to_active(vma, ring);
		if (obj->base.write_domain) {
			obj->dirty = 1;
			obj->last_write_seqno = seqno;

			intel_fb_obj_invalidate(obj, ring);

			/* update for the implicit flush after a batch */
			obj->base.write_domain &= ~I915_GEM_GPU_DOMAINS;
		}
		if (entry->flags & EXEC_OBJECT_NEEDS_FENCE) {
			obj->last_fenced_seqno = seqno;
			if (entry->flags & __EXEC_OBJECT_HAS_FENCE) {
				struct drm_i915_private *dev_priv = to_i915(ring->dev);
				list_move_tail(&dev_priv->fence_regs[obj->fence_reg].lru_list,
					       &dev_priv->mm.fence_list);
			}
		}

		trace_i915_gem_object_change_domain(obj, old_read, old_write);
	}
}

static void
i915_gem_execbuffer_retire_commands(struct drm_device *dev,
				    struct drm_file *file,
				    struct intel_engine_cs *ring,
				    struct drm_i915_gem_object *obj)
{
	/* Unconditionally force add_request to emit a full flush. */
	ring->gpu_caches_dirty = true;

	/* Add a breadcrumb for the completion of the batch buffer */
	(void)__i915_add_request(ring, file, obj, NULL);
}

static int
i915_reset_gen7_sol_offsets(struct drm_device *dev,
			    struct intel_engine_cs *ring)
{
	struct drm_i915_private *dev_priv = dev->dev_private;
	int ret, i;

	if (!IS_GEN7(dev) || ring != &dev_priv->ring[RCS]) {
		DRM_DEBUG("sol reset is gen7/rcs only\n");
		return -EINVAL;
	}

	ret = intel_ring_begin(ring, 4 * 3);
	if (ret)
		return ret;

	for (i = 0; i < 4; i++) {
		intel_ring_emit(ring, MI_LOAD_REGISTER_IMM(1));
		intel_ring_emit(ring, GEN7_SO_WRITE_OFFSET(i));
		intel_ring_emit(ring, 0);
	}

	intel_ring_advance(ring);

	return 0;
}

static int
legacy_ringbuffer_submission(struct drm_device *dev, struct drm_file *file,
			     struct intel_engine_cs *ring,
			     struct intel_context *ctx,
			     struct drm_i915_gem_execbuffer2 *args,
			     struct list_head *vmas,
			     struct drm_i915_gem_object *batch_obj,
			     u64 exec_start, u32 flags)
{
	struct drm_clip_rect *cliprects = NULL;
	struct drm_i915_private *dev_priv = dev->dev_private;
	u64 exec_len;
	int instp_mode;
	u32 instp_mask;
	int i, ret = 0;

	if (args->num_cliprects != 0) {
		if (ring != &dev_priv->ring[RCS]) {
			DRM_DEBUG("clip rectangles are only valid with the render ring\n");
			return -EINVAL;
		}

		if (INTEL_INFO(dev)->gen >= 5) {
			DRM_DEBUG("clip rectangles are only valid on pre-gen5\n");
			return -EINVAL;
		}

		if (args->num_cliprects > UINT_MAX / sizeof(*cliprects)) {
			DRM_DEBUG("execbuf with %u cliprects\n",
				  args->num_cliprects);
			return -EINVAL;
		}

		cliprects = kcalloc(args->num_cliprects,
				    sizeof(*cliprects),
				    GFP_KERNEL);
		if (cliprects == NULL) {
			ret = -ENOMEM;
			goto error;
		}

		if (copy_from_user(cliprects,
				   to_user_ptr(args->cliprects_ptr),
				   sizeof(*cliprects)*args->num_cliprects)) {
			ret = -EFAULT;
			goto error;
		}
	} else {
		if (args->DR4 == 0xffffffff) {
			DRM_DEBUG("UXA submitting garbage DR4, fixing up\n");
			args->DR4 = 0;
		}

		if (args->DR1 || args->DR4 || args->cliprects_ptr) {
			DRM_DEBUG("0 cliprects but dirt in cliprects fields\n");
			return -EINVAL;
		}
	}

	ret = i915_gem_execbuffer_move_to_gpu(ring, vmas);
	if (ret)
		goto error;

	ret = i915_switch_context(ring, ctx);
	if (ret)
		goto error;

	instp_mode = args->flags & I915_EXEC_CONSTANTS_MASK;
	instp_mask = I915_EXEC_CONSTANTS_MASK;
	switch (instp_mode) {
	case I915_EXEC_CONSTANTS_REL_GENERAL:
	case I915_EXEC_CONSTANTS_ABSOLUTE:
	case I915_EXEC_CONSTANTS_REL_SURFACE:
		if (instp_mode != 0 && ring != &dev_priv->ring[RCS]) {
			DRM_DEBUG("non-0 rel constants mode on non-RCS\n");
			ret = -EINVAL;
			goto error;
		}

		if (instp_mode != dev_priv->relative_constants_mode) {
			if (INTEL_INFO(dev)->gen < 4) {
				DRM_DEBUG("no rel constants on pre-gen4\n");
				ret = -EINVAL;
				goto error;
			}

			if (INTEL_INFO(dev)->gen > 5 &&
			    instp_mode == I915_EXEC_CONSTANTS_REL_SURFACE) {
				DRM_DEBUG("rel surface constants mode invalid on gen5+\n");
				ret = -EINVAL;
				goto error;
			}

			/* The HW changed the meaning on this bit on gen6 */
			if (INTEL_INFO(dev)->gen >= 6)
				instp_mask &= ~I915_EXEC_CONSTANTS_REL_SURFACE;
		}
		break;
	default:
		DRM_DEBUG("execbuf with unknown constants: %d\n", instp_mode);
		ret = -EINVAL;
		goto error;
	}

	if (ring == &dev_priv->ring[RCS] &&
			instp_mode != dev_priv->relative_constants_mode) {
		ret = intel_ring_begin(ring, 4);
		if (ret)
			goto error;

		intel_ring_emit(ring, MI_NOOP);
		intel_ring_emit(ring, MI_LOAD_REGISTER_IMM(1));
		intel_ring_emit(ring, INSTPM);
		intel_ring_emit(ring, instp_mask << 16 | instp_mode);
		intel_ring_advance(ring);

		dev_priv->relative_constants_mode = instp_mode;
	}

	if (args->flags & I915_EXEC_GEN7_SOL_RESET) {
		ret = i915_reset_gen7_sol_offsets(dev, ring);
		if (ret)
			goto error;
	}

	exec_len = args->batch_len;
	if (cliprects) {
		for (i = 0; i < args->num_cliprects; i++) {
			ret = i915_emit_box(dev, &cliprects[i],
					    args->DR1, args->DR4);
			if (ret)
				goto error;

			ret = ring->dispatch_execbuffer(ring,
							exec_start, exec_len,
							flags);
			if (ret)
				goto error;
		}
	} else {
		ret = ring->dispatch_execbuffer(ring,
						exec_start, exec_len,
						flags);
		if (ret)
			return ret;
	}

	trace_i915_gem_ring_dispatch(ring, intel_ring_get_seqno(ring), flags);

	i915_gem_execbuffer_move_to_active(vmas, ring);
	i915_gem_execbuffer_retire_commands(dev, file, ring, batch_obj);

error:
	kfree(cliprects);
	return ret;
}

/**
 * Find one BSD ring to dispatch the corresponding BSD command.
 * The Ring ID is returned.
 */
static int gen8_dispatch_bsd_ring(struct drm_device *dev,
				  struct drm_file *file)
{
	struct drm_i915_private *dev_priv = dev->dev_private;
	struct drm_i915_file_private *file_priv = file->driver_priv;

	/* Check whether the file_priv is using one ring */
	if (file_priv->bsd_ring)
		return file_priv->bsd_ring->id;
	else {
		/* If no, use the ping-pong mechanism to select one ring */
		int ring_id;

		mutex_lock(&dev->struct_mutex);
		if (dev_priv->mm.bsd_ring_dispatch_index == 0) {
			ring_id = VCS;
			dev_priv->mm.bsd_ring_dispatch_index = 1;
		} else {
			ring_id = VCS2;
			dev_priv->mm.bsd_ring_dispatch_index = 0;
		}
		file_priv->bsd_ring = &dev_priv->ring[ring_id];
		mutex_unlock(&dev->struct_mutex);
		return ring_id;
	}
}

static struct drm_i915_gem_object *
eb_get_batch(struct eb_vmas *eb)
{
	struct i915_vma *vma = list_entry(eb->vmas.prev, typeof(*vma), exec_list);

	/*
	 * SNA is doing fancy tricks with compressing batch buffers, which leads
	 * to negative relocation deltas. Usually that works out ok since the
	 * relocate address is still positive, except when the batch is placed
	 * very low in the GTT. Ensure this doesn't happen.
	 *
	 * Note that actual hangs have only been observed on gen7, but for
	 * paranoia do it everywhere.
	 */
	vma->exec_entry->flags |= __EXEC_OBJECT_NEEDS_BIAS;

	return vma->obj;
}

static int
i915_gem_do_execbuffer(struct drm_device *dev, void *data,
		       struct drm_file *file,
		       struct drm_i915_gem_execbuffer2 *args,
		       struct drm_i915_gem_exec_object2 *exec)
{
	struct drm_i915_private *dev_priv = dev->dev_private;
	struct eb_vmas *eb;
	struct drm_i915_gem_object *batch_obj;
	struct intel_engine_cs *ring;
	struct intel_context *ctx;
	struct i915_address_space *vm;
	const u32 ctx_id = i915_execbuffer2_get_context_id(*args);
	u64 exec_start = args->batch_start_offset;
	u32 flags;
	int ret;
	bool need_relocs;

	if (!i915_gem_check_execbuffer(args))
		return -EINVAL;

	ret = validate_exec_list(exec, args->buffer_count);
	if (ret)
		return ret;

	flags = 0;
	if (args->flags & I915_EXEC_SECURE) {
		if (!file->is_master || !capable(CAP_SYS_ADMIN))
		    return -EPERM;

		flags |= I915_DISPATCH_SECURE;
	}
	if (args->flags & I915_EXEC_IS_PINNED)
		flags |= I915_DISPATCH_PINNED;

	if ((args->flags & I915_EXEC_RING_MASK) > LAST_USER_RING) {
		DRM_DEBUG("execbuf with unknown ring: %d\n",
			  (int)(args->flags & I915_EXEC_RING_MASK));
		return -EINVAL;
	}

	if ((args->flags & I915_EXEC_RING_MASK) == I915_EXEC_DEFAULT)
		ring = &dev_priv->ring[RCS];
	else if ((args->flags & I915_EXEC_RING_MASK) == I915_EXEC_BSD) {
		if (HAS_BSD2(dev)) {
			int ring_id;
			ring_id = gen8_dispatch_bsd_ring(dev, file);
			ring = &dev_priv->ring[ring_id];
		} else
			ring = &dev_priv->ring[VCS];
	} else
		ring = &dev_priv->ring[(args->flags & I915_EXEC_RING_MASK) - 1];

	if (!intel_ring_initialized(ring)) {
		DRM_DEBUG("execbuf with invalid ring: %d\n",
			  (int)(args->flags & I915_EXEC_RING_MASK));
		return -EINVAL;
	}

	if (args->buffer_count < 1) {
		DRM_DEBUG("execbuf with %d buffers\n", args->buffer_count);
		return -EINVAL;
	}

	intel_runtime_pm_get(dev_priv);

	ret = i915_mutex_lock_interruptible(dev);
	if (ret)
		goto pre_mutex_err;

	if (dev_priv->ums.mm_suspended) {
		mutex_unlock(&dev->struct_mutex);
		ret = -EBUSY;
		goto pre_mutex_err;
	}

	ctx = i915_gem_validate_context(dev, file, ring, ctx_id);
	if (IS_ERR(ctx)) {
		mutex_unlock(&dev->struct_mutex);
		ret = PTR_ERR(ctx);
		goto pre_mutex_err;
	}

	i915_gem_context_reference(ctx);

	vm = ctx->vm;
	if (!USES_FULL_PPGTT(dev))
		vm = &dev_priv->gtt.base;

	eb = eb_create(args);
	if (eb == NULL) {
		i915_gem_context_unreference(ctx);
		mutex_unlock(&dev->struct_mutex);
		ret = -ENOMEM;
		goto pre_mutex_err;
	}

	/* Look up object handles */
	ret = eb_lookup_vmas(eb, exec, args, vm, file);
	if (ret)
		goto err;

	/* take note of the batch buffer before we might reorder the lists */
	batch_obj = eb_get_batch(eb);

	/* Move the objects en-masse into the GTT, evicting if necessary. */
	need_relocs = (args->flags & I915_EXEC_NO_RELOC) == 0;
	ret = i915_gem_execbuffer_reserve(ring, &eb->vmas, &need_relocs);
	if (ret)
		goto err;

	/* The objects are in their final locations, apply the relocations. */
	if (need_relocs)
		ret = i915_gem_execbuffer_relocate(eb);
	if (ret) {
		if (ret == -EFAULT) {
			ret = i915_gem_execbuffer_relocate_slow(dev, args, file, ring,
								eb, exec);
			BUG_ON(!mutex_is_locked(&dev->struct_mutex));
		}
		if (ret)
			goto err;
	}

	/* Set the pending read domains for the batch buffer to COMMAND */
	if (batch_obj->base.pending_write_domain) {
		DRM_DEBUG("Attempting to use self-modifying batch buffer\n");
		ret = -EINVAL;
		goto err;
	}
	batch_obj->base.pending_read_domains |= I915_GEM_DOMAIN_COMMAND;

	if (i915_needs_cmd_parser(ring)) {
		ret = i915_parse_cmds(ring,
				      batch_obj,
				      args->batch_start_offset,
				      file->is_master);
		if (ret)
			goto err;

		/*
		 * XXX: Actually do this when enabling batch copy...
		 *
		 * Set the DISPATCH_SECURE bit to remove the NON_SECURE bit
		 * from MI_BATCH_BUFFER_START commands issued in the
		 * dispatch_execbuffer implementations. We specifically don't
		 * want that set when the command parser is enabled.
		 */
	}

	/* snb/ivb/vlv conflate the "batch in ppgtt" bit with the "non-secure
	 * batch" bit. Hence we need to pin secure batches into the global gtt.
	 * hsw should have this fixed, but bdw mucks it up again. */
	if (flags & I915_DISPATCH_SECURE &&
	    !batch_obj->has_global_gtt_mapping) {
		/* When we have multiple VMs, we'll need to make sure that we
		 * allocate space first */
		struct i915_vma *vma = i915_gem_obj_to_ggtt(batch_obj);
		BUG_ON(!vma);
		vma->bind_vma(vma, batch_obj->cache_level, GLOBAL_BIND);
	}

	if (flags & I915_DISPATCH_SECURE)
		exec_start += i915_gem_obj_ggtt_offset(batch_obj);
	else
		exec_start += i915_gem_obj_offset(batch_obj, vm);

	ret = legacy_ringbuffer_submission(dev, file, ring, ctx,
			args, &eb->vmas, batch_obj, exec_start, flags);
	if (ret)
		goto err;

err:
	/* the request owns the ref now */
	i915_gem_context_unreference(ctx);
	eb_destroy(eb);

	mutex_unlock(&dev->struct_mutex);

pre_mutex_err:
	/* intel_gpu_busy should also get a ref, so it will free when the device
	 * is really idle. */
	intel_runtime_pm_put(dev_priv);
	return ret;
}

/*
 * Legacy execbuffer just creates an exec2 list from the original exec object
 * list array and passes it to the real function.
 */
int
i915_gem_execbuffer(struct drm_device *dev, void *data,
		    struct drm_file *file)
{
	struct drm_i915_gem_execbuffer *args = data;
	struct drm_i915_gem_execbuffer2 exec2;
	struct drm_i915_gem_exec_object *exec_list = NULL;
	struct drm_i915_gem_exec_object2 *exec2_list = NULL;
	int ret, i;

	if (args->buffer_count < 1) {
		DRM_DEBUG("execbuf with %d buffers\n", args->buffer_count);
		return -EINVAL;
	}

	/* Copy in the exec list from userland */
	exec_list = drm_malloc_ab(sizeof(*exec_list), args->buffer_count);
	exec2_list = drm_malloc_ab(sizeof(*exec2_list), args->buffer_count);
	if (exec_list == NULL || exec2_list == NULL) {
		DRM_DEBUG("Failed to allocate exec list for %d buffers\n",
			  args->buffer_count);
		drm_free_large(exec_list);
		drm_free_large(exec2_list);
		return -ENOMEM;
	}
	ret = copy_from_user(exec_list,
			     to_user_ptr(args->buffers_ptr),
			     sizeof(*exec_list) * args->buffer_count);
	if (ret != 0) {
		DRM_DEBUG("copy %d exec entries failed %d\n",
			  args->buffer_count, ret);
		drm_free_large(exec_list);
		drm_free_large(exec2_list);
		return -EFAULT;
	}

	for (i = 0; i < args->buffer_count; i++) {
		exec2_list[i].handle = exec_list[i].handle;
		exec2_list[i].relocation_count = exec_list[i].relocation_count;
		exec2_list[i].relocs_ptr = exec_list[i].relocs_ptr;
		exec2_list[i].alignment = exec_list[i].alignment;
		exec2_list[i].offset = exec_list[i].offset;
		if (INTEL_INFO(dev)->gen < 4)
			exec2_list[i].flags = EXEC_OBJECT_NEEDS_FENCE;
		else
			exec2_list[i].flags = 0;
	}

	exec2.buffers_ptr = args->buffers_ptr;
	exec2.buffer_count = args->buffer_count;
	exec2.batch_start_offset = args->batch_start_offset;
	exec2.batch_len = args->batch_len;
	exec2.DR1 = args->DR1;
	exec2.DR4 = args->DR4;
	exec2.num_cliprects = args->num_cliprects;
	exec2.cliprects_ptr = args->cliprects_ptr;
	exec2.flags = I915_EXEC_RENDER;
	i915_execbuffer2_set_context_id(exec2, 0);

	ret = i915_gem_do_execbuffer(dev, data, file, &exec2, exec2_list);
	if (!ret) {
		struct drm_i915_gem_exec_object __user *user_exec_list =
			to_user_ptr(args->buffers_ptr);

		/* Copy the new buffer offsets back to the user's exec list. */
		for (i = 0; i < args->buffer_count; i++) {
			ret = __copy_to_user(&user_exec_list[i].offset,
					     &exec2_list[i].offset,
					     sizeof(user_exec_list[i].offset));
			if (ret) {
				ret = -EFAULT;
				DRM_DEBUG("failed to copy %d exec entries "
					  "back to user (%d)\n",
					  args->buffer_count, ret);
				break;
			}
		}
	}

	drm_free_large(exec_list);
	drm_free_large(exec2_list);
	return ret;
}

int
i915_gem_execbuffer2(struct drm_device *dev, void *data,
		     struct drm_file *file)
{
	struct drm_i915_gem_execbuffer2 *args = data;
	struct drm_i915_gem_exec_object2 *exec2_list = NULL;
	int ret;

	if (args->buffer_count < 1 ||
	    args->buffer_count > UINT_MAX / sizeof(*exec2_list)) {
		DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
		return -EINVAL;
	}

	if (args->rsvd2 != 0) {
		DRM_DEBUG("dirty rvsd2 field\n");
		return -EINVAL;
	}

	exec2_list = kmalloc(sizeof(*exec2_list)*args->buffer_count,
			     GFP_TEMPORARY | __GFP_NOWARN | __GFP_NORETRY);
	if (exec2_list == NULL)
		exec2_list = drm_malloc_ab(sizeof(*exec2_list),
					   args->buffer_count);
	if (exec2_list == NULL) {
		DRM_DEBUG("Failed to allocate exec list for %d buffers\n",
			  args->buffer_count);
		return -ENOMEM;
	}
	ret = copy_from_user(exec2_list,
			     to_user_ptr(args->buffers_ptr),
			     sizeof(*exec2_list) * args->buffer_count);
	if (ret != 0) {
		DRM_DEBUG("copy %d exec entries failed %d\n",
			  args->buffer_count, ret);
		drm_free_large(exec2_list);
		return -EFAULT;
	}

	ret = i915_gem_do_execbuffer(dev, data, file, args, exec2_list);
	if (!ret) {
		/* Copy the new buffer offsets back to the user's exec list. */
		struct drm_i915_gem_exec_object2 __user *user_exec_list =
				   to_user_ptr(args->buffers_ptr);
		int i;

		for (i = 0; i < args->buffer_count; i++) {
			ret = __copy_to_user(&user_exec_list[i].offset,
					     &exec2_list[i].offset,
					     sizeof(user_exec_list[i].offset));
			if (ret) {
				ret = -EFAULT;
				DRM_DEBUG("failed to copy %d exec entries "
					  "back to user\n",
					  args->buffer_count);
				break;
			}
		}
	}

	drm_free_large(exec2_list);
	return ret;
}