drm/i915: Eliminate lots of iterations over the execobjects array

[uclinux-h8/linux.git] / 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 <linux/dma_remapping.h>
#include <linux/reservation.h>
#include <linux/sync_file.h>
#include <linux/uaccess.h>

#include <drm/drmP.h>
#include <drm/i915_drm.h>

#include "i915_drv.h"
#include "i915_gem_clflush.h"
#include "i915_trace.h"
#include "intel_drv.h"
#include "intel_frontbuffer.h"

#define DBG_USE_CPU_RELOC 0 /* -1 force GTT relocs; 1 force CPU relocs */

#define __EXEC_OBJECT_HAS_PIN           BIT(31)
#define __EXEC_OBJECT_HAS_FENCE         BIT(30)
#define __EXEC_OBJECT_NEEDS_MAP         BIT(29)
#define __EXEC_OBJECT_NEEDS_BIAS        BIT(28)
#define __EXEC_OBJECT_INTERNAL_FLAGS    (~0u << 28) /* all of the above */
#define __EXEC_OBJECT_RESERVED (__EXEC_OBJECT_HAS_PIN | __EXEC_OBJECT_HAS_FENCE)

#define __EXEC_HAS_RELOC        BIT(31)
#define __EXEC_VALIDATED        BIT(30)
#define UPDATE                  PIN_OFFSET_FIXED

#define BATCH_OFFSET_BIAS (256*1024)

#define __I915_EXEC_ILLEGAL_FLAGS \
        (__I915_EXEC_UNKNOWN_FLAGS | I915_EXEC_CONSTANTS_MASK)

/**
 * DOC: User command execution
 *
 * Userspace submits commands to be executed on the GPU as an instruction
 * stream within a GEM object we call a batchbuffer. This instructions may
 * refer to other GEM objects containing auxiliary state such as kernels,
 * samplers, render targets and even secondary batchbuffers. Userspace does
 * not know where in the GPU memory these objects reside and so before the
 * batchbuffer is passed to the GPU for execution, those addresses in the
 * batchbuffer and auxiliary objects are updated. This is known as relocation,
 * or patching. To try and avoid having to relocate each object on the next
 * execution, userspace is told the location of those objects in this pass,
 * but this remains just a hint as the kernel may choose a new location for
 * any object in the future.
 *
 * Processing an execbuf ioctl is conceptually split up into a few phases.
 *
 * 1. Validation - Ensure all the pointers, handles and flags are valid.
 * 2. Reservation - Assign GPU address space for every object
 * 3. Relocation - Update any addresses to point to the final locations
 * 4. Serialisation - Order the request with respect to its dependencies
 * 5. Construction - Construct a request to execute the batchbuffer
 * 6. Submission (at some point in the future execution)
 *
 * Reserving resources for the execbuf is the most complicated phase. We
 * neither want to have to migrate the object in the address space, nor do
 * we want to have to update any relocations pointing to this object. Ideally,
 * we want to leave the object where it is and for all the existing relocations
 * to match. If the object is given a new address, or if userspace thinks the
 * object is elsewhere, we have to parse all the relocation entries and update
 * the addresses. Userspace can set the I915_EXEC_NORELOC flag to hint that
 * all the target addresses in all of its objects match the value in the
 * relocation entries and that they all match the presumed offsets given by the
 * list of execbuffer objects. Using this knowledge, we know that if we haven't
 * moved any buffers, all the relocation entries are valid and we can skip
 * the update. (If userspace is wrong, the likely outcome is an impromptu GPU
 * hang.) The requirement for using I915_EXEC_NO_RELOC are:
 *
 *      The addresses written in the objects must match the corresponding
 *      reloc.presumed_offset which in turn must match the corresponding
 *      execobject.offset.
 *
 *      Any render targets written to in the batch must be flagged with
 *      EXEC_OBJECT_WRITE.
 *
 *      To avoid stalling, execobject.offset should match the current
 *      address of that object within the active context.
 *
 * The reservation is done is multiple phases. First we try and keep any
 * object already bound in its current location - so as long as meets the
 * constraints imposed by the new execbuffer. Any object left unbound after the
 * first pass is then fitted into any available idle space. If an object does
 * not fit, all objects are removed from the reservation and the process rerun
 * after sorting the objects into a priority order (more difficult to fit
 * objects are tried first). Failing that, the entire VM is cleared and we try
 * to fit the execbuf once last time before concluding that it simply will not
 * fit.
 *
 * A small complication to all of this is that we allow userspace not only to
 * specify an alignment and a size for the object in the address space, but
 * we also allow userspace to specify the exact offset. This objects are
 * simpler to place (the location is known a priori) all we have to do is make
 * sure the space is available.
 *
 * Once all the objects are in place, patching up the buried pointers to point
 * to the final locations is a fairly simple job of walking over the relocation
 * entry arrays, looking up the right address and rewriting the value into
 * the object. Simple! ... The relocation entries are stored in user memory
 * and so to access them we have to copy them into a local buffer. That copy
 * has to avoid taking any pagefaults as they may lead back to a GEM object
 * requiring the struct_mutex (i.e. recursive deadlock). So once again we split
 * the relocation into multiple passes. First we try to do everything within an
 * atomic context (avoid the pagefaults) which requires that we never wait. If
 * we detect that we may wait, or if we need to fault, then we have to fallback
 * to a slower path. The slowpath has to drop the mutex. (Can you hear alarm
 * bells yet?) Dropping the mutex means that we lose all the state we have
 * built up so far for the execbuf and we must reset any global data. However,
 * we do leave the objects pinned in their final locations - which is a
 * potential issue for concurrent execbufs. Once we have left the mutex, we can
 * allocate and copy all the relocation entries into a large array at our
 * leisure, reacquire the mutex, reclaim all the objects and other state and
 * then proceed to update any incorrect addresses with the objects.
 *
 * As we process the relocation entries, we maintain a record of whether the
 * object is being written to. Using NORELOC, we expect userspace to provide
 * this information instead. We also check whether we can skip the relocation
 * by comparing the expected value inside the relocation entry with the target's
 * final address. If they differ, we have to map the current object and rewrite
 * the 4 or 8 byte pointer within.
 *
 * Serialising an execbuf is quite simple according to the rules of the GEM
 * ABI. Execution within each context is ordered by the order of submission.
 * Writes to any GEM object are in order of submission and are exclusive. Reads
 * from a GEM object are unordered with respect to other reads, but ordered by
 * writes. A write submitted after a read cannot occur before the read, and
 * similarly any read submitted after a write cannot occur before the write.
 * Writes are ordered between engines such that only one write occurs at any
 * time (completing any reads beforehand) - using semaphores where available
 * and CPU serialisation otherwise. Other GEM access obey the same rules, any
 * write (either via mmaps using set-domain, or via pwrite) must flush all GPU
 * reads before starting, and any read (either using set-domain or pread) must
 * flush all GPU writes before starting. (Note we only employ a barrier before,
 * we currently rely on userspace not concurrently starting a new execution
 * whilst reading or writing to an object. This may be an advantage or not
 * depending on how much you trust userspace not to shoot themselves in the
 * foot.) Serialisation may just result in the request being inserted into
 * a DAG awaiting its turn, but most simple is to wait on the CPU until
 * all dependencies are resolved.
 *
 * After all of that, is just a matter of closing the request and handing it to
 * the hardware (well, leaving it in a queue to be executed). However, we also
 * offer the ability for batchbuffers to be run with elevated privileges so
 * that they access otherwise hidden registers. (Used to adjust L3 cache etc.)
 * Before any batch is given extra privileges we first must check that it
 * contains no nefarious instructions, we check that each instruction is from
 * our whitelist and all registers are also from an allowed list. We first
 * copy the user's batchbuffer to a shadow (so that the user doesn't have
 * access to it, either by the CPU or GPU as we scan it) and then parse each
 * instruction. If everything is ok, we set a flag telling the hardware to run
 * the batchbuffer in trusted mode, otherwise the ioctl is rejected.
 */

struct i915_execbuffer {
        struct drm_i915_private *i915; /** i915 backpointer */
        struct drm_file *file; /** per-file lookup tables and limits */
        struct drm_i915_gem_execbuffer2 *args; /** ioctl parameters */
        struct drm_i915_gem_exec_object2 *exec; /** ioctl execobj[] */

        struct intel_engine_cs *engine; /** engine to queue the request to */
        struct i915_gem_context *ctx; /** context for building the request */
        struct i915_address_space *vm; /** GTT and vma for the request */

        struct drm_i915_gem_request *request; /** our request to build */
        struct i915_vma *batch; /** identity of the batch obj/vma */

        /** actual size of execobj[] as we may extend it for the cmdparser */
        unsigned int buffer_count;

        /** list of vma not yet bound during reservation phase */
        struct list_head unbound;

        /** list of vma that have execobj.relocation_count */
        struct list_head relocs;

        /**
         * Track the most recently used object for relocations, as we
         * frequently have to perform multiple relocations within the same
         * obj/page
         */
        struct reloc_cache {
                struct drm_mm_node node; /** temporary GTT binding */
                unsigned long vaddr; /** Current kmap address */
                unsigned long page; /** Currently mapped page index */
                bool use_64bit_reloc : 1;
                bool has_llc : 1;
                bool has_fence : 1;
                bool needs_unfenced : 1;
        } reloc_cache;

        u64 invalid_flags; /** Set of execobj.flags that are invalid */
        u32 context_flags; /** Set of execobj.flags to insert from the ctx */

        u32 batch_start_offset; /** Location within object of batch */
        u32 batch_len; /** Length of batch within object */
        u32 batch_flags; /** Flags composed for emit_bb_start() */

        /**
         * Indicate either the size of the hastable used to resolve
         * relocation handles, or if negative that we are using a direct
         * index into the execobj[].
         */
        int lut_size;
        struct hlist_head *buckets; /** ht for relocation handles */
};

/*
 * As an alternative to creating a hashtable of handle-to-vma for a batch,
 * we used the last available reserved field in the execobject[] and stash
 * a link from the execobj to its vma.
 */
#define __exec_to_vma(ee) (ee)->rsvd2
#define exec_to_vma(ee) u64_to_ptr(struct i915_vma, __exec_to_vma(ee))

/*
 * Used to convert any address to canonical form.
 * Starting from gen8, some commands (e.g. STATE_BASE_ADDRESS,
 * MI_LOAD_REGISTER_MEM and others, see Broadwell PRM Vol2a) require the
 * addresses to be in a canonical form:
 * "GraphicsAddress[63:48] are ignored by the HW and assumed to be in correct
 * canonical form [63:48] == [47]."
 */
#define GEN8_HIGH_ADDRESS_BIT 47
static inline u64 gen8_canonical_addr(u64 address)
{
        return sign_extend64(address, GEN8_HIGH_ADDRESS_BIT);
}

static inline u64 gen8_noncanonical_addr(u64 address)
{
        return address & GENMASK_ULL(GEN8_HIGH_ADDRESS_BIT, 0);
}

static int eb_create(struct i915_execbuffer *eb)
{
        if (!(eb->args->flags & I915_EXEC_HANDLE_LUT)) {
                unsigned int size = 1 + ilog2(eb->buffer_count);

                /*
                 * Without a 1:1 association between relocation handles and
                 * the execobject[] index, we instead create a hashtable.
                 * We size it dynamically based on available memory, starting
                 * first with 1:1 assocative hash and scaling back until
                 * the allocation succeeds.
                 *
                 * Later on we use a positive lut_size to indicate we are
                 * using this hashtable, and a negative value to indicate a
                 * direct lookup.
                 */
                do {
                        eb->buckets = kzalloc(sizeof(struct hlist_head) << size,
                                              GFP_TEMPORARY |
                                              __GFP_NORETRY |
                                              __GFP_NOWARN);
                        if (eb->buckets)
                                break;
                } while (--size);

                if (unlikely(!eb->buckets)) {
                        eb->buckets = kzalloc(sizeof(struct hlist_head),
                                              GFP_TEMPORARY);
                        if (unlikely(!eb->buckets))
                                return -ENOMEM;
                }

                eb->lut_size = size;
        } else {
                eb->lut_size = -eb->buffer_count;
        }

        return 0;
}

static bool
eb_vma_misplaced(const struct drm_i915_gem_exec_object2 *entry,
                 const struct i915_vma *vma)
{
        if (!(entry->flags & __EXEC_OBJECT_HAS_PIN))
                return true;

        if (vma->node.size < entry->pad_to_size)
                return true;

        if (entry->alignment && !IS_ALIGNED(vma->node.start, entry->alignment))
                return true;

        if (entry->flags & EXEC_OBJECT_PINNED &&
            vma->node.start != entry->offset)
                return true;

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

        if (!(entry->flags & EXEC_OBJECT_SUPPORTS_48B_ADDRESS) &&
            (vma->node.start + vma->node.size - 1) >> 32)
                return true;

        return false;
}

static inline void
eb_pin_vma(struct i915_execbuffer *eb,
           struct drm_i915_gem_exec_object2 *entry,
           struct i915_vma *vma)
{
        u64 flags;

        flags = vma->node.start;
        flags |= PIN_USER | PIN_NONBLOCK | PIN_OFFSET_FIXED;
        if (unlikely(entry->flags & EXEC_OBJECT_NEEDS_GTT))
                flags |= PIN_GLOBAL;
        if (unlikely(i915_vma_pin(vma, 0, 0, flags)))
                return;

        if (unlikely(entry->flags & EXEC_OBJECT_NEEDS_FENCE)) {
                if (unlikely(i915_vma_get_fence(vma))) {
                        i915_vma_unpin(vma);
                        return;
                }

                if (i915_vma_pin_fence(vma))
                        entry->flags |= __EXEC_OBJECT_HAS_FENCE;
        }

        entry->flags |= __EXEC_OBJECT_HAS_PIN;
}

static inline void
__eb_unreserve_vma(struct i915_vma *vma,
                   const struct drm_i915_gem_exec_object2 *entry)
{
        GEM_BUG_ON(!(entry->flags & __EXEC_OBJECT_HAS_PIN));

        if (unlikely(entry->flags & __EXEC_OBJECT_HAS_FENCE))
                i915_vma_unpin_fence(vma);

        __i915_vma_unpin(vma);
}

static inline void
eb_unreserve_vma(struct i915_vma *vma,
                 struct drm_i915_gem_exec_object2 *entry)
{
        if (!(entry->flags & __EXEC_OBJECT_HAS_PIN))
                return;

        __eb_unreserve_vma(vma, entry);
        entry->flags &= ~__EXEC_OBJECT_RESERVED;
}

static int
eb_validate_vma(struct i915_execbuffer *eb,
                struct drm_i915_gem_exec_object2 *entry,
                struct i915_vma *vma)
{
        if (unlikely(entry->flags & eb->invalid_flags))
                return -EINVAL;

        if (unlikely(entry->alignment && !is_power_of_2(entry->alignment)))
                return -EINVAL;

        /*
         * Offset can be used as input (EXEC_OBJECT_PINNED), reject
         * any non-page-aligned or non-canonical addresses.
         */
        if (unlikely(entry->flags & EXEC_OBJECT_PINNED &&
                     entry->offset != gen8_canonical_addr(entry->offset & PAGE_MASK)))
                return -EINVAL;

        /* pad_to_size was once a reserved field, so sanitize it */
        if (entry->flags & EXEC_OBJECT_PAD_TO_SIZE) {
                if (unlikely(offset_in_page(entry->pad_to_size)))
                        return -EINVAL;
        } else {
                entry->pad_to_size = 0;
        }

        if (unlikely(vma->exec_entry)) {
                DRM_DEBUG("Object [handle %d, index %d] appears more than once in object list\n",
                          entry->handle, (int)(entry - eb->exec));
                return -EINVAL;
        }

        /*
         * From drm_mm perspective address space is continuous,
         * so from this point we're always using non-canonical
         * form internally.
         */
        entry->offset = gen8_noncanonical_addr(entry->offset);

        return 0;
}

static int
eb_add_vma(struct i915_execbuffer *eb,
           struct drm_i915_gem_exec_object2 *entry,
           struct i915_vma *vma)
{
        int err;

        GEM_BUG_ON(i915_vma_is_closed(vma));

        if (!(eb->args->flags & __EXEC_VALIDATED)) {
                err = eb_validate_vma(eb, entry, vma);
                if (unlikely(err))
                        return err;
        }

        if (eb->lut_size >= 0) {
                vma->exec_handle = entry->handle;
                hlist_add_head(&vma->exec_node,
                               &eb->buckets[hash_32(entry->handle,
                                                    eb->lut_size)]);
        }

        if (entry->relocation_count)
                list_add_tail(&vma->reloc_link, &eb->relocs);

        if (!eb->reloc_cache.has_fence) {
                entry->flags &= ~EXEC_OBJECT_NEEDS_FENCE;
        } else {
                if ((entry->flags & EXEC_OBJECT_NEEDS_FENCE ||
                     eb->reloc_cache.needs_unfenced) &&
                    i915_gem_object_is_tiled(vma->obj))
                        entry->flags |= EXEC_OBJECT_NEEDS_GTT | __EXEC_OBJECT_NEEDS_MAP;
        }

        if (!(entry->flags & EXEC_OBJECT_PINNED))
                entry->flags |= eb->context_flags;

        /*
         * Stash a pointer from the vma to execobj, so we can query its flags,
         * size, alignment etc as provided by the user. Also we stash a pointer
         * to the vma inside the execobj so that we can use a direct lookup
         * to find the right target VMA when doing relocations.
         */
        vma->exec_entry = entry;
        __exec_to_vma(entry) = (uintptr_t)i915_vma_get(vma);

        err = 0;
        if (vma->node.size)
                eb_pin_vma(eb, entry, vma);
        if (eb_vma_misplaced(entry, vma)) {
                eb_unreserve_vma(vma, entry);

                list_add_tail(&vma->exec_link, &eb->unbound);
                if (drm_mm_node_allocated(&vma->node))
                        err = i915_vma_unbind(vma);
        } else {
                if (entry->offset != vma->node.start) {
                        entry->offset = vma->node.start | UPDATE;
                        eb->args->flags |= __EXEC_HAS_RELOC;
                }
        }
        return err;
}

static inline int use_cpu_reloc(const struct reloc_cache *cache,
                                const struct drm_i915_gem_object *obj)
{
        if (!i915_gem_object_has_struct_page(obj))
                return false;

        if (DBG_USE_CPU_RELOC)
                return DBG_USE_CPU_RELOC > 0;

        return (cache->has_llc ||
                obj->cache_dirty ||
                obj->cache_level != I915_CACHE_NONE);
}

static int eb_reserve_vma(const struct i915_execbuffer *eb,
                          struct i915_vma *vma)
{
        struct drm_i915_gem_exec_object2 *entry = vma->exec_entry;
        u64 flags;
        int err;

        flags = PIN_USER | PIN_NONBLOCK;
        if (entry->flags & EXEC_OBJECT_NEEDS_GTT)
                flags |= PIN_GLOBAL;

        /*
         * Wa32bitGeneralStateOffset & Wa32bitInstructionBaseOffset,
         * limit address to the first 4GBs for unflagged objects.
         */
        if (!(entry->flags & EXEC_OBJECT_SUPPORTS_48B_ADDRESS))
                flags |= PIN_ZONE_4G;

        if (entry->flags & __EXEC_OBJECT_NEEDS_MAP)
                flags |= PIN_MAPPABLE;

        if (entry->flags & EXEC_OBJECT_PINNED) {
                flags |= entry->offset | PIN_OFFSET_FIXED;
                flags &= ~PIN_NONBLOCK; /* force overlapping PINNED checks */
        } else if (entry->flags & __EXEC_OBJECT_NEEDS_BIAS) {
                flags |= BATCH_OFFSET_BIAS | PIN_OFFSET_BIAS;
        }

        err = i915_vma_pin(vma, entry->pad_to_size, entry->alignment, flags);
        if (err)
                return err;

        if (entry->offset != vma->node.start) {
                entry->offset = vma->node.start | UPDATE;
                eb->args->flags |= __EXEC_HAS_RELOC;
        }

        entry->flags |= __EXEC_OBJECT_HAS_PIN;
        GEM_BUG_ON(eb_vma_misplaced(entry, vma));

        if (unlikely(entry->flags & EXEC_OBJECT_NEEDS_FENCE)) {
                err = i915_vma_get_fence(vma);
                if (unlikely(err)) {
                        i915_vma_unpin(vma);
                        return err;
                }

                if (i915_vma_pin_fence(vma))
                        entry->flags |= __EXEC_OBJECT_HAS_FENCE;
        }

        return 0;
}

static int eb_reserve(struct i915_execbuffer *eb)
{
        const unsigned int count = eb->buffer_count;
        struct list_head last;
        struct i915_vma *vma;
        unsigned int i, pass;
        int err;

        /*
         * 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.
         */

        pass = 0;
        err = 0;
        do {
                list_for_each_entry(vma, &eb->unbound, exec_link) {
                        err = eb_reserve_vma(eb, vma);
                        if (err)
                                break;
                }
                if (err != -ENOSPC)
                        return err;

                /* Resort *all* the objects into priority order */
                INIT_LIST_HEAD(&eb->unbound);
                INIT_LIST_HEAD(&last);
                for (i = 0; i < count; i++) {
                        struct drm_i915_gem_exec_object2 *entry = &eb->exec[i];

                        if (entry->flags & EXEC_OBJECT_PINNED &&
                            entry->flags & __EXEC_OBJECT_HAS_PIN)
                                continue;

                        vma = exec_to_vma(entry);
                        eb_unreserve_vma(vma, entry);

                        if (entry->flags & EXEC_OBJECT_PINNED)
                                list_add(&vma->exec_link, &eb->unbound);
                        else if (entry->flags & __EXEC_OBJECT_NEEDS_MAP)
                                list_add_tail(&vma->exec_link, &eb->unbound);
                        else
                                list_add_tail(&vma->exec_link, &last);
                }
                list_splice_tail(&last, &eb->unbound);

                switch (pass++) {
                case 0:
                        break;

                case 1:
                        /* Too fragmented, unbind everything and retry */
                        err = i915_gem_evict_vm(eb->vm);
                        if (err)
                                return err;
                        break;

                default:
                        return -ENOSPC;
                }
        } while (1);
}

static inline struct hlist_head *
ht_head(const  struct i915_gem_context_vma_lut *lut, u32 handle)
{
        return &lut->ht[hash_32(handle, lut->ht_bits)];
}

static inline bool
ht_needs_resize(const struct i915_gem_context_vma_lut *lut)
{
        return (4*lut->ht_count > 3*lut->ht_size ||
                4*lut->ht_count + 1 < lut->ht_size);
}

static unsigned int eb_batch_index(const struct i915_execbuffer *eb)
{
        return eb->buffer_count - 1;
}

static int eb_select_context(struct i915_execbuffer *eb)
{
        struct i915_gem_context *ctx;

        ctx = i915_gem_context_lookup(eb->file->driver_priv, eb->args->rsvd1);
        if (unlikely(IS_ERR(ctx)))
                return PTR_ERR(ctx);

        if (unlikely(i915_gem_context_is_banned(ctx))) {
                DRM_DEBUG("Context %u tried to submit while banned\n",
                          ctx->user_handle);
                return -EIO;
        }

        eb->ctx = i915_gem_context_get(ctx);
        eb->vm = ctx->ppgtt ? &ctx->ppgtt->base : &eb->i915->ggtt.base;

        eb->context_flags = 0;
        if (ctx->flags & CONTEXT_NO_ZEROMAP)
                eb->context_flags |= __EXEC_OBJECT_NEEDS_BIAS;

        return 0;
}

static int eb_lookup_vmas(struct i915_execbuffer *eb)
{
#define INTERMEDIATE BIT(0)
        const unsigned int count = eb->buffer_count;
        struct i915_gem_context_vma_lut *lut = &eb->ctx->vma_lut;
        struct i915_vma *vma;
        struct idr *idr;
        unsigned int i;
        int slow_pass = -1;
        int err;

        INIT_LIST_HEAD(&eb->relocs);
        INIT_LIST_HEAD(&eb->unbound);

        if (unlikely(lut->ht_size & I915_CTX_RESIZE_IN_PROGRESS))
                flush_work(&lut->resize);
        GEM_BUG_ON(lut->ht_size & I915_CTX_RESIZE_IN_PROGRESS);

        for (i = 0; i < count; i++) {
                __exec_to_vma(&eb->exec[i]) = 0;

                hlist_for_each_entry(vma,
                                     ht_head(lut, eb->exec[i].handle),
                                     ctx_node) {
                        if (vma->ctx_handle != eb->exec[i].handle)
                                continue;

                        err = eb_add_vma(eb, &eb->exec[i], vma);
                        if (unlikely(err))
                                return err;

                        goto next_vma;
                }

                if (slow_pass < 0)
                        slow_pass = i;
next_vma: ;
        }

        if (slow_pass < 0)
                goto out;

        spin_lock(&eb->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
         */
        idr = &eb->file->object_idr;
        for (i = slow_pass; i < count; i++) {
                struct drm_i915_gem_object *obj;

                if (__exec_to_vma(&eb->exec[i]))
                        continue;

                obj = to_intel_bo(idr_find(idr, eb->exec[i].handle));
                if (unlikely(!obj)) {
                        spin_unlock(&eb->file->table_lock);
                        DRM_DEBUG("Invalid object handle %d at index %d\n",
                                  eb->exec[i].handle, i);
                        err = -ENOENT;
                        goto err;
                }

                __exec_to_vma(&eb->exec[i]) = INTERMEDIATE | (uintptr_t)obj;
        }
        spin_unlock(&eb->file->table_lock);

        for (i = slow_pass; i < count; i++) {
                struct drm_i915_gem_object *obj;

                if (!(__exec_to_vma(&eb->exec[i]) & INTERMEDIATE))
                        continue;

                /*
                 * 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.
                 */
                obj = u64_to_ptr(typeof(*obj),
                                 __exec_to_vma(&eb->exec[i]) & ~INTERMEDIATE);
                vma = i915_vma_instance(obj, eb->vm, NULL);
                if (unlikely(IS_ERR(vma))) {
                        DRM_DEBUG("Failed to lookup VMA\n");
                        err = PTR_ERR(vma);
                        goto err;
                }

                /* First come, first served */
                if (!vma->ctx) {
                        vma->ctx = eb->ctx;
                        vma->ctx_handle = eb->exec[i].handle;
                        hlist_add_head(&vma->ctx_node,
                                       ht_head(lut, eb->exec[i].handle));
                        lut->ht_count++;
                        lut->ht_size |= I915_CTX_RESIZE_IN_PROGRESS;
                        if (i915_vma_is_ggtt(vma)) {
                                GEM_BUG_ON(obj->vma_hashed);
                                obj->vma_hashed = vma;
                        }
                }

                err = eb_add_vma(eb, &eb->exec[i], vma);
                if (unlikely(err))
                        goto err;
        }

        if (lut->ht_size & I915_CTX_RESIZE_IN_PROGRESS) {
                if (ht_needs_resize(lut))
                        queue_work(system_highpri_wq, &lut->resize);
                else
                        lut->ht_size &= ~I915_CTX_RESIZE_IN_PROGRESS;
        }

out:
        /* take note of the batch buffer before we might reorder the lists */
        i = eb_batch_index(eb);
        eb->batch = exec_to_vma(&eb->exec[i]);

        /*
         * 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.
         */
        if (!(eb->exec[i].flags & EXEC_OBJECT_PINNED))
                eb->exec[i].flags |= __EXEC_OBJECT_NEEDS_BIAS;
        if (eb->reloc_cache.has_fence)
                eb->exec[i].flags |= EXEC_OBJECT_NEEDS_FENCE;

        eb->args->flags |= __EXEC_VALIDATED;
        return eb_reserve(eb);

err:
        for (i = slow_pass; i < count; i++) {
                if (__exec_to_vma(&eb->exec[i]) & INTERMEDIATE)
                        __exec_to_vma(&eb->exec[i]) = 0;
        }
        lut->ht_size &= ~I915_CTX_RESIZE_IN_PROGRESS;
        return err;
#undef INTERMEDIATE
}

static struct i915_vma *
eb_get_vma(const struct i915_execbuffer *eb, unsigned long handle)
{
        if (eb->lut_size < 0) {
                if (handle >= -eb->lut_size)
                        return NULL;
                return exec_to_vma(&eb->exec[handle]);
        } else {
                struct hlist_head *head;
                struct i915_vma *vma;

                head = &eb->buckets[hash_32(handle, eb->lut_size)];
                hlist_for_each_entry(vma, head, exec_node) {
                        if (vma->exec_handle == handle)
                                return vma;
                }
                return NULL;
        }
}

static void eb_release_vmas(const struct i915_execbuffer *eb)
{
        const unsigned int count = eb->buffer_count;
        unsigned int i;

        for (i = 0; i < count; i++) {
                struct drm_i915_gem_exec_object2 *entry = &eb->exec[i];
                struct i915_vma *vma = exec_to_vma(entry);

                if (!vma)
                        continue;

                GEM_BUG_ON(vma->exec_entry != entry);
                vma->exec_entry = NULL;

                eb_unreserve_vma(vma, entry);

                i915_vma_put(vma);
        }
}

static void eb_reset_vmas(const struct i915_execbuffer *eb)
{
        eb_release_vmas(eb);
        if (eb->lut_size >= 0)
                memset(eb->buckets, 0,
                       sizeof(struct hlist_head) << eb->lut_size);
}

static void eb_destroy(const struct i915_execbuffer *eb)
{
        if (eb->lut_size >= 0)
                kfree(eb->buckets);
}

static inline u64
relocation_target(const struct drm_i915_gem_relocation_entry *reloc,
                  const struct i915_vma *target)
{
        return gen8_canonical_addr((int)reloc->delta + target->node.start);
}

static void reloc_cache_init(struct reloc_cache *cache,
                             struct drm_i915_private *i915)
{
        cache->page = -1;
        cache->vaddr = 0;
        /* Must be a variable in the struct to allow GCC to unroll. */
        cache->has_llc = HAS_LLC(i915);
        cache->has_fence = INTEL_GEN(i915) < 4;
        cache->needs_unfenced = INTEL_INFO(i915)->unfenced_needs_alignment;
        cache->use_64bit_reloc = HAS_64BIT_RELOC(i915);
        cache->node.allocated = false;
}

static inline void *unmask_page(unsigned long p)
{
        return (void *)(uintptr_t)(p & PAGE_MASK);
}

static inline unsigned int unmask_flags(unsigned long p)
{
        return p & ~PAGE_MASK;
}

#define KMAP 0x4 /* after CLFLUSH_FLAGS */

static inline struct i915_ggtt *cache_to_ggtt(struct reloc_cache *cache)
{
        struct drm_i915_private *i915 =
                container_of(cache, struct i915_execbuffer, reloc_cache)->i915;
        return &i915->ggtt;
}

static void reloc_cache_reset(struct reloc_cache *cache)
{
        void *vaddr;

        if (!cache->vaddr)
                return;

        vaddr = unmask_page(cache->vaddr);
        if (cache->vaddr & KMAP) {
                if (cache->vaddr & CLFLUSH_AFTER)
                        mb();

                kunmap_atomic(vaddr);
                i915_gem_obj_finish_shmem_access((struct drm_i915_gem_object *)cache->node.mm);
        } else {
                wmb();
                io_mapping_unmap_atomic((void __iomem *)vaddr);
                if (cache->node.allocated) {
                        struct i915_ggtt *ggtt = cache_to_ggtt(cache);

                        ggtt->base.clear_range(&ggtt->base,
                                               cache->node.start,
                                               cache->node.size);
                        drm_mm_remove_node(&cache->node);
                } else {
                        i915_vma_unpin((struct i915_vma *)cache->node.mm);
                }
        }

        cache->vaddr = 0;
        cache->page = -1;
}

static void *reloc_kmap(struct drm_i915_gem_object *obj,
                        struct reloc_cache *cache,
                        unsigned long page)
{
        void *vaddr;

        if (cache->vaddr) {
                kunmap_atomic(unmask_page(cache->vaddr));
        } else {
                unsigned int flushes;
                int err;

                err = i915_gem_obj_prepare_shmem_write(obj, &flushes);
                if (err)
                        return ERR_PTR(err);

                BUILD_BUG_ON(KMAP & CLFLUSH_FLAGS);
                BUILD_BUG_ON((KMAP | CLFLUSH_FLAGS) & PAGE_MASK);

                cache->vaddr = flushes | KMAP;
                cache->node.mm = (void *)obj;
                if (flushes)
                        mb();
        }

        vaddr = kmap_atomic(i915_gem_object_get_dirty_page(obj, page));
        cache->vaddr = unmask_flags(cache->vaddr) | (unsigned long)vaddr;
        cache->page = page;

        return vaddr;
}

static void *reloc_iomap(struct drm_i915_gem_object *obj,
                         struct reloc_cache *cache,
                         unsigned long page)
{
        struct i915_ggtt *ggtt = cache_to_ggtt(cache);
        unsigned long offset;
        void *vaddr;

        if (cache->vaddr) {
                io_mapping_unmap_atomic((void __force __iomem *) unmask_page(cache->vaddr));
        } else {
                struct i915_vma *vma;
                int err;

                if (use_cpu_reloc(cache, obj))
                        return NULL;

                err = i915_gem_object_set_to_gtt_domain(obj, true);
                if (err)
                        return ERR_PTR(err);

                vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,
                                               PIN_MAPPABLE | PIN_NONBLOCK);
                if (IS_ERR(vma)) {
                        memset(&cache->node, 0, sizeof(cache->node));
                        err = drm_mm_insert_node_in_range
                                (&ggtt->base.mm, &cache->node,
                                 PAGE_SIZE, 0, I915_COLOR_UNEVICTABLE,
                                 0, ggtt->mappable_end,
                                 DRM_MM_INSERT_LOW);
                        if (err) /* no inactive aperture space, use cpu reloc */
                                return NULL;
                } else {
                        err = i915_vma_put_fence(vma);
                        if (err) {
                                i915_vma_unpin(vma);
                                return ERR_PTR(err);
                        }

                        cache->node.start = vma->node.start;
                        cache->node.mm = (void *)vma;
                }
        }

        offset = cache->node.start;
        if (cache->node.allocated) {
                wmb();
                ggtt->base.insert_page(&ggtt->base,
                                       i915_gem_object_get_dma_address(obj, page),
                                       offset, I915_CACHE_NONE, 0);
        } else {
                offset += page << PAGE_SHIFT;
        }

        vaddr = (void __force *)io_mapping_map_atomic_wc(&ggtt->mappable,
                                                         offset);
        cache->page = page;
        cache->vaddr = (unsigned long)vaddr;

        return vaddr;
}

static void *reloc_vaddr(struct drm_i915_gem_object *obj,
                         struct reloc_cache *cache,
                         unsigned long page)
{
        void *vaddr;

        if (cache->page == page) {
                vaddr = unmask_page(cache->vaddr);
        } else {
                vaddr = NULL;
                if ((cache->vaddr & KMAP) == 0)
                        vaddr = reloc_iomap(obj, cache, page);
                if (!vaddr)
                        vaddr = reloc_kmap(obj, cache, page);
        }

        return vaddr;
}

static void clflush_write32(u32 *addr, u32 value, unsigned int flushes)
{
        if (unlikely(flushes & (CLFLUSH_BEFORE | CLFLUSH_AFTER))) {
                if (flushes & CLFLUSH_BEFORE) {
                        clflushopt(addr);
                        mb();
                }

                *addr = value;

                /*
                 * Writes to the same cacheline are serialised by the CPU
                 * (including clflush). On the write path, we only require
                 * that it hits memory in an orderly fashion and place
                 * mb barriers at the start and end of the relocation phase
                 * to ensure ordering of clflush wrt to the system.
                 */
                if (flushes & CLFLUSH_AFTER)
                        clflushopt(addr);
        } else
                *addr = value;
}

static u64
relocate_entry(struct i915_vma *vma,
               const struct drm_i915_gem_relocation_entry *reloc,
               struct i915_execbuffer *eb,
               const struct i915_vma *target)
{
        struct drm_i915_gem_object *obj = vma->obj;
        u64 offset = reloc->offset;
        u64 target_offset = relocation_target(reloc, target);
        bool wide = eb->reloc_cache.use_64bit_reloc;
        void *vaddr;

repeat:
        vaddr = reloc_vaddr(obj, &eb->reloc_cache, offset >> PAGE_SHIFT);
        if (IS_ERR(vaddr))
                return PTR_ERR(vaddr);

        clflush_write32(vaddr + offset_in_page(offset),
                        lower_32_bits(target_offset),
                        eb->reloc_cache.vaddr);

        if (wide) {
                offset += sizeof(u32);
                target_offset >>= 32;
                wide = false;
                goto repeat;
        }

        return target->node.start | UPDATE;
}

static u64
eb_relocate_entry(struct i915_execbuffer *eb,
                  struct i915_vma *vma,
                  const struct drm_i915_gem_relocation_entry *reloc)
{
        struct i915_vma *target;
        int err;

        /* we've already hold a reference to all valid objects */
        target = eb_get_vma(eb, reloc->target_handle);
        if (unlikely(!target))
                return -ENOENT;

        /* 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: "
                          "target %d offset %d "
                          "read %08x write %08x",
                          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: "
                          "target %d offset %d "
                          "read %08x write %08x",
                          reloc->target_handle,
                          (int) reloc->offset,
                          reloc->read_domains,
                          reloc->write_domain);
                return -EINVAL;
        }

        if (reloc->write_domain) {
                target->exec_entry->flags |= EXEC_OBJECT_WRITE;

                /*
                 * 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 (reloc->write_domain == I915_GEM_DOMAIN_INSTRUCTION &&
                    IS_GEN6(eb->i915)) {
                        err = i915_vma_bind(target, target->obj->cache_level,
                                            PIN_GLOBAL);
                        if (WARN_ONCE(err,
                                      "Unexpected failure to bind target VMA!"))
                                return err;
                }
        }

        /*
         * If the relocation already has the right value in it, no
         * more work needs to be done.
         */
        if (gen8_canonical_addr(target->node.start) == reloc->presumed_offset)
                return 0;

        /* Check that the relocation address is valid... */
        if (unlikely(reloc->offset >
                     vma->size - (eb->reloc_cache.use_64bit_reloc ? 8 : 4))) {
                DRM_DEBUG("Relocation beyond object bounds: "
                          "target %d offset %d size %d.\n",
                          reloc->target_handle,
                          (int)reloc->offset,
                          (int)vma->size);
                return -EINVAL;
        }
        if (unlikely(reloc->offset & 3)) {
                DRM_DEBUG("Relocation not 4-byte aligned: "
                          "target %d offset %d.\n",
                          reloc->target_handle,
                          (int)reloc->offset);
                return -EINVAL;
        }

        /*
         * If we write into the object, we need to force the synchronisation
         * barrier, either with an asynchronous clflush or if we executed the
         * patching using the GPU (though that should be serialised by the
         * timeline). To be completely sure, and since we are required to
         * do relocations we are already stalling, disable the user's opt
         * of our synchronisation.
         */
        vma->exec_entry->flags &= ~EXEC_OBJECT_ASYNC;

        /* and update the user's relocation entry */
        return relocate_entry(vma, reloc, eb, target);
}

static int eb_relocate_vma(struct i915_execbuffer *eb, struct i915_vma *vma)
{
#define N_RELOC(x) ((x) / sizeof(struct drm_i915_gem_relocation_entry))
        struct drm_i915_gem_relocation_entry stack[N_RELOC(512)];
        struct drm_i915_gem_relocation_entry __user *urelocs;
        const struct drm_i915_gem_exec_object2 *entry = vma->exec_entry;
        unsigned int remain;

        urelocs = u64_to_user_ptr(entry->relocs_ptr);
        remain = entry->relocation_count;
        if (unlikely(remain > N_RELOC(ULONG_MAX)))
                return -EINVAL;

        /*
         * We must check that the entire relocation array is safe
         * to read. However, if the array is not writable the user loses
         * the updated relocation values.
         */
        if (unlikely(!access_ok(VERIFY_READ, urelocs, remain*sizeof(urelocs))))
                return -EFAULT;

        do {
                struct drm_i915_gem_relocation_entry *r = stack;
                unsigned int count =
                        min_t(unsigned int, remain, ARRAY_SIZE(stack));
                unsigned int copied;

                /*
                 * 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();
                copied = __copy_from_user_inatomic(r, urelocs, count * sizeof(r[0]));
                pagefault_enable();
                if (unlikely(copied)) {
                        remain = -EFAULT;
                        goto out;
                }

                remain -= count;
                do {
                        u64 offset = eb_relocate_entry(eb, vma, r);

                        if (likely(offset == 0)) {
                        } else if ((s64)offset < 0) {
                                remain = (int)offset;
                                goto out;
                        } else {
                                /*
                                 * Note that reporting an error now
                                 * leaves everything in an inconsistent
                                 * state as we have *already* changed
                                 * the relocation value inside the
                                 * object. As we have not changed the
                                 * reloc.presumed_offset or will not
                                 * change the execobject.offset, on the
                                 * call we may not rewrite the value
                                 * inside the object, leaving it
                                 * dangling and causing a GPU hang. Unless
                                 * userspace dynamically rebuilds the
                                 * relocations on each execbuf rather than
                                 * presume a static tree.
                                 *
                                 * We did previously check if the relocations
                                 * were writable (access_ok), an error now
                                 * would be a strange race with mprotect,
                                 * having already demonstrated that we
                                 * can read from this userspace address.
                                 */
                                offset = gen8_canonical_addr(offset & ~UPDATE);
                                __put_user(offset,
                                           &urelocs[r-stack].presumed_offset);
                        }
                } while (r++, --count);
                urelocs += ARRAY_SIZE(stack);
        } while (remain);
out:
        reloc_cache_reset(&eb->reloc_cache);
        return remain;
}

static int
eb_relocate_vma_slow(struct i915_execbuffer *eb, struct i915_vma *vma)
{
        const struct drm_i915_gem_exec_object2 *entry = vma->exec_entry;
        struct drm_i915_gem_relocation_entry *relocs =
                u64_to_ptr(typeof(*relocs), entry->relocs_ptr);
        unsigned int i;
        int err;

        for (i = 0; i < entry->relocation_count; i++) {
                u64 offset = eb_relocate_entry(eb, vma, &relocs[i]);

                if ((s64)offset < 0) {
                        err = (int)offset;
                        goto err;
                }
        }
        err = 0;
err:
        reloc_cache_reset(&eb->reloc_cache);
        return err;
}

static int check_relocations(const struct drm_i915_gem_exec_object2 *entry)
{
        const char __user *addr, *end;
        unsigned long size;
        char __maybe_unused c;

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

        if (size > N_RELOC(ULONG_MAX))
                return -EINVAL;

        addr = u64_to_user_ptr(entry->relocs_ptr);
        size *= sizeof(struct drm_i915_gem_relocation_entry);
        if (!access_ok(VERIFY_READ, addr, size))
                return -EFAULT;

        end = addr + size;
        for (; addr < end; addr += PAGE_SIZE) {
                int err = __get_user(c, addr);
                if (err)
                        return err;
        }
        return __get_user(c, end - 1);
}

static int eb_copy_relocations(const struct i915_execbuffer *eb)
{
        const unsigned int count = eb->buffer_count;
        unsigned int i;
        int err;

        for (i = 0; i < count; i++) {
                const unsigned int nreloc = eb->exec[i].relocation_count;
                struct drm_i915_gem_relocation_entry __user *urelocs;
                struct drm_i915_gem_relocation_entry *relocs;
                unsigned long size;
                unsigned long copied;

                if (nreloc == 0)
                        continue;

                err = check_relocations(&eb->exec[i]);
                if (err)
                        goto err;

                urelocs = u64_to_user_ptr(eb->exec[i].relocs_ptr);
                size = nreloc * sizeof(*relocs);

                relocs = kvmalloc_array(size, 1, GFP_TEMPORARY);
                if (!relocs) {
                        kvfree(relocs);
                        err = -ENOMEM;
                        goto err;
                }

                /* copy_from_user is limited to < 4GiB */
                copied = 0;
                do {
                        unsigned int len =
                                min_t(u64, BIT_ULL(31), size - copied);

                        if (__copy_from_user((char *)relocs + copied,
                                             (char *)urelocs + copied,
                                             len)) {
                                kvfree(relocs);
                                err = -EFAULT;
                                goto err;
                        }

                        copied += len;
                } while (copied < size);

                /*
                 * 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.
                 */
                user_access_begin();
                for (copied = 0; copied < nreloc; copied++)
                        unsafe_put_user(-1,
                                        &urelocs[copied].presumed_offset,
                                        end_user);
end_user:
                user_access_end();

                eb->exec[i].relocs_ptr = (uintptr_t)relocs;
        }

        return 0;

err:
        while (i--) {
                struct drm_i915_gem_relocation_entry *relocs =
                        u64_to_ptr(typeof(*relocs), eb->exec[i].relocs_ptr);
                if (eb->exec[i].relocation_count)
                        kvfree(relocs);
        }
        return err;
}

static int eb_prefault_relocations(const struct i915_execbuffer *eb)
{
        const unsigned int count = eb->buffer_count;
        unsigned int i;

        if (unlikely(i915.prefault_disable))
                return 0;

        for (i = 0; i < count; i++) {
                int err;

                err = check_relocations(&eb->exec[i]);
                if (err)
                        return err;
        }

        return 0;
}

static noinline int eb_relocate_slow(struct i915_execbuffer *eb)
{
        struct drm_device *dev = &eb->i915->drm;
        bool have_copy = false;
        struct i915_vma *vma;
        int err = 0;

repeat:
        if (signal_pending(current)) {
                err = -ERESTARTSYS;
                goto out;
        }

        /* We may process another execbuffer during the unlock... */
        eb_reset_vmas(eb);
        mutex_unlock(&dev->struct_mutex);

        /*
         * We take 3 passes through the slowpatch.
         *
         * 1 - we try to just prefault all the user relocation entries and
         * then attempt to reuse the atomic pagefault disabled fast path again.
         *
         * 2 - we copy the user entries to a local buffer here outside of the
         * local and allow ourselves to wait upon any rendering before
         * relocations
         *
         * 3 - we already have a local copy of the relocation entries, but
         * were interrupted (EAGAIN) whilst waiting for the objects, try again.
         */
        if (!err) {
                err = eb_prefault_relocations(eb);
        } else if (!have_copy) {
                err = eb_copy_relocations(eb);
                have_copy = err == 0;
        } else {
                cond_resched();
                err = 0;
        }
        if (err) {
                mutex_lock(&dev->struct_mutex);
                goto out;
        }

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

        /* reacquire the objects */
        err = eb_lookup_vmas(eb);
        if (err)
                goto err;

        list_for_each_entry(vma, &eb->relocs, reloc_link) {
                if (!have_copy) {
                        pagefault_disable();
                        err = eb_relocate_vma(eb, vma);
                        pagefault_enable();
                        if (err)
                                goto repeat;
                } else {
                        err = eb_relocate_vma_slow(eb, vma);
                        if (err)
                                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:
        if (err == -EAGAIN)
                goto repeat;

out:
        if (have_copy) {
                const unsigned int count = eb->buffer_count;
                unsigned int i;

                for (i = 0; i < count; i++) {
                        const struct drm_i915_gem_exec_object2 *entry =
                                &eb->exec[i];
                        struct drm_i915_gem_relocation_entry *relocs;

                        if (!entry->relocation_count)
                                continue;

                        relocs = u64_to_ptr(typeof(*relocs), entry->relocs_ptr);
                        kvfree(relocs);
                }
        }

        return err ?: have_copy;
}

static int eb_relocate(struct i915_execbuffer *eb)
{
        if (eb_lookup_vmas(eb))
                goto slow;

        /* The objects are in their final locations, apply the relocations. */
        if (eb->args->flags & __EXEC_HAS_RELOC) {
                struct i915_vma *vma;

                list_for_each_entry(vma, &eb->relocs, reloc_link) {
                        if (eb_relocate_vma(eb, vma))
                                goto slow;
                }
        }

        return 0;

slow:
        return eb_relocate_slow(eb);
}

static void eb_export_fence(struct drm_i915_gem_object *obj,
                            struct drm_i915_gem_request *req,
                            unsigned int flags)
{
        struct reservation_object *resv = obj->resv;

        /*
         * Ignore errors from failing to allocate the new fence, we can't
         * handle an error right now. Worst case should be missed
         * synchronisation leading to rendering corruption.
         */
        reservation_object_lock(resv, NULL);
        if (flags & EXEC_OBJECT_WRITE)
                reservation_object_add_excl_fence(resv, &req->fence);
        else if (reservation_object_reserve_shared(resv) == 0)
                reservation_object_add_shared_fence(resv, &req->fence);
        reservation_object_unlock(resv);
}

static int eb_move_to_gpu(struct i915_execbuffer *eb)
{
        const unsigned int count = eb->buffer_count;
        unsigned int i;
        int err;

        for (i = 0; i < count; i++) {
                const struct drm_i915_gem_exec_object2 *entry = &eb->exec[i];
                struct i915_vma *vma = exec_to_vma(entry);
                struct drm_i915_gem_object *obj = vma->obj;

                if (entry->flags & EXEC_OBJECT_CAPTURE) {
                        struct i915_gem_capture_list *capture;

                        capture = kmalloc(sizeof(*capture), GFP_KERNEL);
                        if (unlikely(!capture))
                                return -ENOMEM;

                        capture->next = eb->request->capture_list;
                        capture->vma = vma;
                        eb->request->capture_list = capture;
                }

                if (entry->flags & EXEC_OBJECT_ASYNC)
                        goto skip_flushes;

                if (unlikely(obj->cache_dirty && !obj->cache_coherent))
                        i915_gem_clflush_object(obj, 0);

                err = i915_gem_request_await_object
                        (eb->request, obj, entry->flags & EXEC_OBJECT_WRITE);
                if (err)
                        return err;

skip_flushes:
                i915_vma_move_to_active(vma, eb->request, entry->flags);
                __eb_unreserve_vma(vma, entry);
                vma->exec_entry = NULL;
        }

        for (i = 0; i < count; i++) {
                const struct drm_i915_gem_exec_object2 *entry = &eb->exec[i];
                struct i915_vma *vma = exec_to_vma(entry);

                eb_export_fence(vma->obj, eb->request, entry->flags);
                i915_vma_put(vma);
        }
        eb->exec = NULL;

        /* Unconditionally flush any chipset caches (for streaming writes). */
        i915_gem_chipset_flush(eb->i915);

        /* Unconditionally invalidate GPU caches and TLBs. */
        return eb->engine->emit_flush(eb->request, EMIT_INVALIDATE);
}

static bool i915_gem_check_execbuffer(struct drm_i915_gem_execbuffer2 *exec)
{
        if (exec->flags & __I915_EXEC_ILLEGAL_FLAGS)
                return false;

        /* Kernel clipping was a DRI1 misfeature */
        if (exec->num_cliprects || exec->cliprects_ptr)
                return false;

        if (exec->DR4 == 0xffffffff) {
                DRM_DEBUG("UXA submitting garbage DR4, fixing up\n");
                exec->DR4 = 0;
        }
        if (exec->DR1 || exec->DR4)
                return false;

        if ((exec->batch_start_offset | exec->batch_len) & 0x7)
                return false;

        return true;
}

void i915_vma_move_to_active(struct i915_vma *vma,
                             struct drm_i915_gem_request *req,
                             unsigned int flags)
{
        struct drm_i915_gem_object *obj = vma->obj;
        const unsigned int idx = req->engine->id;

        lockdep_assert_held(&req->i915->drm.struct_mutex);
        GEM_BUG_ON(!drm_mm_node_allocated(&vma->node));

        /*
         * Add a reference if we're newly entering the active list.
         * The order in which we add operations to the retirement queue is
         * vital here: mark_active adds to the start of the callback list,
         * such that subsequent callbacks are called first. Therefore we
         * add the active reference first and queue for it to be dropped
         * *last*.
         */
        if (!i915_vma_is_active(vma))
                obj->active_count++;
        i915_vma_set_active(vma, idx);
        i915_gem_active_set(&vma->last_read[idx], req);
        list_move_tail(&vma->vm_link, &vma->vm->active_list);

        obj->base.write_domain = 0;
        if (flags & EXEC_OBJECT_WRITE) {
                obj->base.write_domain = I915_GEM_DOMAIN_RENDER;

                if (intel_fb_obj_invalidate(obj, ORIGIN_CS))
                        i915_gem_active_set(&obj->frontbuffer_write, req);

                obj->base.read_domains = 0;
        }
        obj->base.read_domains |= I915_GEM_GPU_DOMAINS;

        if (flags & EXEC_OBJECT_NEEDS_FENCE)
                i915_gem_active_set(&vma->last_fence, req);
}

static int i915_reset_gen7_sol_offsets(struct drm_i915_gem_request *req)
{
        u32 *cs;
        int i;

        if (!IS_GEN7(req->i915) || req->engine->id != RCS) {
                DRM_DEBUG("sol reset is gen7/rcs only\n");
                return -EINVAL;
        }

        cs = intel_ring_begin(req, 4 * 2 + 2);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        *cs++ = MI_LOAD_REGISTER_IMM(4);
        for (i = 0; i < 4; i++) {
                *cs++ = i915_mmio_reg_offset(GEN7_SO_WRITE_OFFSET(i));
                *cs++ = 0;
        }
        *cs++ = MI_NOOP;
        intel_ring_advance(req, cs);

        return 0;
}

static struct i915_vma *eb_parse(struct i915_execbuffer *eb, bool is_master)
{
        struct drm_i915_gem_object *shadow_batch_obj;
        struct i915_vma *vma;
        int err;

        shadow_batch_obj = i915_gem_batch_pool_get(&eb->engine->batch_pool,
                                                   PAGE_ALIGN(eb->batch_len));
        if (IS_ERR(shadow_batch_obj))
                return ERR_CAST(shadow_batch_obj);

        err = intel_engine_cmd_parser(eb->engine,
                                      eb->batch->obj,
                                      shadow_batch_obj,
                                      eb->batch_start_offset,
                                      eb->batch_len,
                                      is_master);
        if (err) {
                if (err == -EACCES) /* unhandled chained batch */
                        vma = NULL;
                else
                        vma = ERR_PTR(err);
                goto out;
        }

        vma = i915_gem_object_ggtt_pin(shadow_batch_obj, NULL, 0, 0, 0);
        if (IS_ERR(vma))
                goto out;

        vma->exec_entry =
                memset(&eb->exec[eb->buffer_count++],
                       0, sizeof(*vma->exec_entry));
        vma->exec_entry->flags = __EXEC_OBJECT_HAS_PIN;
        __exec_to_vma(vma->exec_entry) = (uintptr_t)i915_vma_get(vma);

out:
        i915_gem_object_unpin_pages(shadow_batch_obj);
        return vma;
}

static void
add_to_client(struct drm_i915_gem_request *req, struct drm_file *file)
{
        req->file_priv = file->driver_priv;
        list_add_tail(&req->client_link, &req->file_priv->mm.request_list);
}

static int eb_submit(struct i915_execbuffer *eb)
{
        int err;

        err = eb_move_to_gpu(eb);
        if (err)
                return err;

        err = i915_switch_context(eb->request);
        if (err)
                return err;

        if (eb->args->flags & I915_EXEC_GEN7_SOL_RESET) {
                err = i915_reset_gen7_sol_offsets(eb->request);
                if (err)
                        return err;
        }

        err = eb->engine->emit_bb_start(eb->request,
                                        eb->batch->node.start +
                                        eb->batch_start_offset,
                                        eb->batch_len,
                                        eb->batch_flags);
        if (err)
                return err;

        return 0;
}

/**
 * Find one BSD ring to dispatch the corresponding BSD command.
 * The engine index is returned.
 */
static unsigned int
gen8_dispatch_bsd_engine(struct drm_i915_private *dev_priv,
                         struct drm_file *file)
{
        struct drm_i915_file_private *file_priv = file->driver_priv;

        /* Check whether the file_priv has already selected one ring. */
        if ((int)file_priv->bsd_engine < 0)
                file_priv->bsd_engine = atomic_fetch_xor(1,
                         &dev_priv->mm.bsd_engine_dispatch_index);

        return file_priv->bsd_engine;
}

#define I915_USER_RINGS (4)

static const enum intel_engine_id user_ring_map[I915_USER_RINGS + 1] = {
        [I915_EXEC_DEFAULT]     = RCS,
        [I915_EXEC_RENDER]      = RCS,
        [I915_EXEC_BLT]         = BCS,
        [I915_EXEC_BSD]         = VCS,
        [I915_EXEC_VEBOX]       = VECS
};

static struct intel_engine_cs *
eb_select_engine(struct drm_i915_private *dev_priv,
                 struct drm_file *file,
                 struct drm_i915_gem_execbuffer2 *args)
{
        unsigned int user_ring_id = args->flags & I915_EXEC_RING_MASK;
        struct intel_engine_cs *engine;

        if (user_ring_id > I915_USER_RINGS) {
                DRM_DEBUG("execbuf with unknown ring: %u\n", user_ring_id);
                return NULL;
        }

        if ((user_ring_id != I915_EXEC_BSD) &&
            ((args->flags & I915_EXEC_BSD_MASK) != 0)) {
                DRM_DEBUG("execbuf with non bsd ring but with invalid "
                          "bsd dispatch flags: %d\n", (int)(args->flags));
                return NULL;
        }

        if (user_ring_id == I915_EXEC_BSD && HAS_BSD2(dev_priv)) {
                unsigned int bsd_idx = args->flags & I915_EXEC_BSD_MASK;

                if (bsd_idx == I915_EXEC_BSD_DEFAULT) {
                        bsd_idx = gen8_dispatch_bsd_engine(dev_priv, file);
                } else if (bsd_idx >= I915_EXEC_BSD_RING1 &&
                           bsd_idx <= I915_EXEC_BSD_RING2) {
                        bsd_idx >>= I915_EXEC_BSD_SHIFT;
                        bsd_idx--;
                } else {
                        DRM_DEBUG("execbuf with unknown bsd ring: %u\n",
                                  bsd_idx);
                        return NULL;
                }

                engine = dev_priv->engine[_VCS(bsd_idx)];
        } else {
                engine = dev_priv->engine[user_ring_map[user_ring_id]];
        }

        if (!engine) {
                DRM_DEBUG("execbuf with invalid ring: %u\n", user_ring_id);
                return NULL;
        }

        return engine;
}

static int
i915_gem_do_execbuffer(struct drm_device *dev,
                       struct drm_file *file,
                       struct drm_i915_gem_execbuffer2 *args,
                       struct drm_i915_gem_exec_object2 *exec)
{
        struct i915_execbuffer eb;
        struct dma_fence *in_fence = NULL;
        struct sync_file *out_fence = NULL;
        int out_fence_fd = -1;
        int err;

        BUILD_BUG_ON(__EXEC_OBJECT_INTERNAL_FLAGS &
                     ~__EXEC_OBJECT_UNKNOWN_FLAGS);

        eb.i915 = to_i915(dev);
        eb.file = file;
        eb.args = args;
        if (!(args->flags & I915_EXEC_NO_RELOC))
                args->flags |= __EXEC_HAS_RELOC;
        eb.exec = exec;
        eb.ctx = NULL;
        eb.invalid_flags = __EXEC_OBJECT_UNKNOWN_FLAGS;
        if (USES_FULL_PPGTT(eb.i915))
                eb.invalid_flags |= EXEC_OBJECT_NEEDS_GTT;
        reloc_cache_init(&eb.reloc_cache, eb.i915);

        eb.buffer_count = args->buffer_count;
        eb.batch_start_offset = args->batch_start_offset;
        eb.batch_len = args->batch_len;

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

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

        eb.engine = eb_select_engine(eb.i915, file, args);
        if (!eb.engine)
                return -EINVAL;

        if (args->flags & I915_EXEC_RESOURCE_STREAMER) {
                if (!HAS_RESOURCE_STREAMER(eb.i915)) {
                        DRM_DEBUG("RS is only allowed for Haswell, Gen8 and above\n");
                        return -EINVAL;
                }
                if (eb.engine->id != RCS) {
                        DRM_DEBUG("RS is not available on %s\n",
                                 eb.engine->name);
                        return -EINVAL;
                }

                eb.batch_flags |= I915_DISPATCH_RS;
        }

        if (args->flags & I915_EXEC_FENCE_IN) {
                in_fence = sync_file_get_fence(lower_32_bits(args->rsvd2));
                if (!in_fence)
                        return -EINVAL;
        }

        if (args->flags & I915_EXEC_FENCE_OUT) {
                out_fence_fd = get_unused_fd_flags(O_CLOEXEC);
                if (out_fence_fd < 0) {
                        err = out_fence_fd;
                        goto err_in_fence;
                }
        }

        if (eb_create(&eb))
                return -ENOMEM;

        /*
         * Take a local wakeref for preparing to dispatch the execbuf as
         * we expect to access the hardware fairly frequently in the
         * process. Upon first dispatch, we acquire another prolonged
         * wakeref that we hold until the GPU has been idle for at least
         * 100ms.
         */
        intel_runtime_pm_get(eb.i915);
        err = i915_mutex_lock_interruptible(dev);
        if (err)
                goto err_rpm;

        err = eb_select_context(&eb);
        if (unlikely(err))
                goto err_unlock;

        err = eb_relocate(&eb);
        if (err)
                /*
                 * If the user expects the execobject.offset and
                 * reloc.presumed_offset to be an exact match,
                 * as for using NO_RELOC, then we cannot update
                 * the execobject.offset until we have completed
                 * relocation.
                 */
                args->flags &= ~__EXEC_HAS_RELOC;
        if (err < 0)
                goto err_vma;

        if (unlikely(eb.batch->exec_entry->flags & EXEC_OBJECT_WRITE)) {
                DRM_DEBUG("Attempting to use self-modifying batch buffer\n");
                err = -EINVAL;
                goto err_vma;
        }
        if (eb.batch_start_offset > eb.batch->size ||
            eb.batch_len > eb.batch->size - eb.batch_start_offset) {
                DRM_DEBUG("Attempting to use out-of-bounds batch\n");
                err = -EINVAL;
                goto err_vma;
        }

        if (eb.engine->needs_cmd_parser && eb.batch_len) {
                struct i915_vma *vma;

                vma = eb_parse(&eb, drm_is_current_master(file));
                if (IS_ERR(vma)) {
                        err = PTR_ERR(vma);
                        goto err_vma;
                }

                if (vma) {
                        /*
                         * Batch parsed and accepted:
                         *
                         * 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 on batches the
                         * command parser has accepted.
                         */
                        eb.batch_flags |= I915_DISPATCH_SECURE;
                        eb.batch_start_offset = 0;
                        eb.batch = vma;
                }
        }

        if (eb.batch_len == 0)
                eb.batch_len = eb.batch->size - eb.batch_start_offset;

        /*
         * 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 (eb.batch_flags & I915_DISPATCH_SECURE) {
                struct i915_vma *vma;

                /*
                 * So on first glance it looks freaky that we pin the batch here
                 * outside of the reservation loop. But:
                 * - The batch is already pinned into the relevant ppgtt, so we
                 *   already have the backing storage fully allocated.
                 * - No other BO uses the global gtt (well contexts, but meh),
                 *   so we don't really have issues with multiple objects not
                 *   fitting due to fragmentation.
                 * So this is actually safe.
                 */
                vma = i915_gem_object_ggtt_pin(eb.batch->obj, NULL, 0, 0, 0);
                if (IS_ERR(vma)) {
                        err = PTR_ERR(vma);
                        goto err_vma;
                }

                eb.batch = vma;
        }

        /* Allocate a request for this batch buffer nice and early. */
        eb.request = i915_gem_request_alloc(eb.engine, eb.ctx);
        if (IS_ERR(eb.request)) {
                err = PTR_ERR(eb.request);
                goto err_batch_unpin;
        }

        if (in_fence) {
                err = i915_gem_request_await_dma_fence(eb.request, in_fence);
                if (err < 0)
                        goto err_request;
        }

        if (out_fence_fd != -1) {
                out_fence = sync_file_create(&eb.request->fence);
                if (!out_fence) {
                        err = -ENOMEM;
                        goto err_request;
                }
        }

        /*
         * Whilst this request exists, batch_obj will be on the
         * active_list, and so will hold the active reference. Only when this
         * request is retired will the the batch_obj be moved onto the
         * inactive_list and lose its active reference. Hence we do not need
         * to explicitly hold another reference here.
         */
        eb.request->batch = eb.batch;

        trace_i915_gem_request_queue(eb.request, eb.batch_flags);
        err = eb_submit(&eb);
err_request:
        __i915_add_request(eb.request, err == 0);
        add_to_client(eb.request, file);

        if (out_fence) {
                if (err == 0) {
                        fd_install(out_fence_fd, out_fence->file);
                        args->rsvd2 &= GENMASK_ULL(0, 31); /* keep in-fence */
                        args->rsvd2 |= (u64)out_fence_fd << 32;
                        out_fence_fd = -1;
                } else {
                        fput(out_fence->file);
                }
        }

err_batch_unpin:
        if (eb.batch_flags & I915_DISPATCH_SECURE)
                i915_vma_unpin(eb.batch);
err_vma:
        if (eb.exec)
                eb_release_vmas(&eb);
        i915_gem_context_put(eb.ctx);
err_unlock:
        mutex_unlock(&dev->struct_mutex);
err_rpm:
        intel_runtime_pm_put(eb.i915);
        eb_destroy(&eb);
        if (out_fence_fd != -1)
                put_unused_fd(out_fence_fd);
err_in_fence:
        dma_fence_put(in_fence);
        return err;
}

/*
 * 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)
{
        const size_t sz = sizeof(struct drm_i915_gem_exec_object2);
        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;
        unsigned int i;
        int err;

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

        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);

        if (!i915_gem_check_execbuffer(&exec2))
                return -EINVAL;

        /* Copy in the exec list from userland */
        exec_list = kvmalloc_array(args->buffer_count, sizeof(*exec_list),
                                   __GFP_NOWARN | GFP_TEMPORARY);
        exec2_list = kvmalloc_array(args->buffer_count + 1, sz,
                                    __GFP_NOWARN | GFP_TEMPORARY);
        if (exec_list == NULL || exec2_list == NULL) {
                DRM_DEBUG("Failed to allocate exec list for %d buffers\n",
                          args->buffer_count);
                kvfree(exec_list);
                kvfree(exec2_list);
                return -ENOMEM;
        }
        err = copy_from_user(exec_list,
                             u64_to_user_ptr(args->buffers_ptr),
                             sizeof(*exec_list) * args->buffer_count);
        if (err) {
                DRM_DEBUG("copy %d exec entries failed %d\n",
                          args->buffer_count, err);
                kvfree(exec_list);
                kvfree(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_GEN(to_i915(dev)) < 4)
                        exec2_list[i].flags = EXEC_OBJECT_NEEDS_FENCE;
                else
                        exec2_list[i].flags = 0;
        }

        err = i915_gem_do_execbuffer(dev, file, &exec2, exec2_list);
        if (exec2.flags & __EXEC_HAS_RELOC) {
                struct drm_i915_gem_exec_object __user *user_exec_list =
                        u64_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++) {
                        if (!(exec2_list[i].offset & UPDATE))
                                continue;

                        exec2_list[i].offset =
                                gen8_canonical_addr(exec2_list[i].offset & PIN_OFFSET_MASK);
                        exec2_list[i].offset &= PIN_OFFSET_MASK;
                        if (__copy_to_user(&user_exec_list[i].offset,
                                           &exec2_list[i].offset,
                                           sizeof(user_exec_list[i].offset)))
                                break;
                }
        }

        kvfree(exec_list);
        kvfree(exec2_list);
        return err;
}

int
i915_gem_execbuffer2(struct drm_device *dev, void *data,
                     struct drm_file *file)
{
        const size_t sz = sizeof(struct drm_i915_gem_exec_object2);
        struct drm_i915_gem_execbuffer2 *args = data;
        struct drm_i915_gem_exec_object2 *exec2_list;
        int err;

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

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

        /* Allocate an extra slot for use by the command parser */
        exec2_list = kvmalloc_array(args->buffer_count + 1, sz,
                                    __GFP_NOWARN | GFP_TEMPORARY);
        if (exec2_list == NULL) {
                DRM_DEBUG("Failed to allocate exec list for %d buffers\n",
                          args->buffer_count);
                return -ENOMEM;
        }
        if (copy_from_user(exec2_list,
                           u64_to_user_ptr(args->buffers_ptr),
                           sizeof(*exec2_list) * args->buffer_count)) {
                DRM_DEBUG("copy %d exec entries failed\n", args->buffer_count);
                kvfree(exec2_list);
                return -EFAULT;
        }

        err = i915_gem_do_execbuffer(dev, file, args, exec2_list);

        /*
         * Now that we have begun execution of the batchbuffer, we ignore
         * any new error after this point. Also given that we have already
         * updated the associated relocations, we try to write out the current
         * object locations irrespective of any error.
         */
        if (args->flags & __EXEC_HAS_RELOC) {
                struct drm_i915_gem_exec_object2 __user *user_exec_list =
                        u64_to_user_ptr(args->buffers_ptr);
                unsigned int i;

                /* Copy the new buffer offsets back to the user's exec list. */
                user_access_begin();
                for (i = 0; i < args->buffer_count; i++) {
                        if (!(exec2_list[i].offset & UPDATE))
                                continue;

                        exec2_list[i].offset =
                                gen8_canonical_addr(exec2_list[i].offset & PIN_OFFSET_MASK);
                        unsafe_put_user(exec2_list[i].offset,
                                        &user_exec_list[i].offset,
                                        end_user);
                }
end_user:
                user_access_end();
        }

        args->flags &= ~__I915_EXEC_UNKNOWN_FLAGS;
        kvfree(exec2_list);
        return err;
}