Merge branch 'kvm-insert-lfence' into kvm-master

[linux.git] / drivers / gpu / drm / i915 / i915_gem.c

/*
 * Copyright © 2008-2015 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 <[email protected]>
 *
 */

#include <drm/drmP.h>
#include <drm/drm_vma_manager.h>
#include <drm/i915_drm.h>
#include "i915_drv.h"
#include "i915_gem_clflush.h"
#include "i915_vgpu.h"
#include "i915_trace.h"
#include "intel_drv.h"
#include "intel_frontbuffer.h"
#include "intel_mocs.h"
#include "i915_gemfs.h"
#include <linux/dma-fence-array.h>
#include <linux/kthread.h>
#include <linux/reservation.h>
#include <linux/shmem_fs.h>
#include <linux/slab.h>
#include <linux/stop_machine.h>
#include <linux/swap.h>
#include <linux/pci.h>
#include <linux/dma-buf.h>

static void i915_gem_flush_free_objects(struct drm_i915_private *i915);

static bool cpu_write_needs_clflush(struct drm_i915_gem_object *obj)
{
        if (obj->cache_dirty)
                return false;

        if (!(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE))
                return true;

        return obj->pin_global; /* currently in use by HW, keep flushed */
}

static int
insert_mappable_node(struct i915_ggtt *ggtt,
                     struct drm_mm_node *node, u32 size)
{
        memset(node, 0, sizeof(*node));
        return drm_mm_insert_node_in_range(&ggtt->base.mm, node,
                                           size, 0, I915_COLOR_UNEVICTABLE,
                                           0, ggtt->mappable_end,
                                           DRM_MM_INSERT_LOW);
}

static void
remove_mappable_node(struct drm_mm_node *node)
{
        drm_mm_remove_node(node);
}

/* some bookkeeping */
static void i915_gem_info_add_obj(struct drm_i915_private *dev_priv,
                                  u64 size)
{
        spin_lock(&dev_priv->mm.object_stat_lock);
        dev_priv->mm.object_count++;
        dev_priv->mm.object_memory += size;
        spin_unlock(&dev_priv->mm.object_stat_lock);
}

static void i915_gem_info_remove_obj(struct drm_i915_private *dev_priv,
                                     u64 size)
{
        spin_lock(&dev_priv->mm.object_stat_lock);
        dev_priv->mm.object_count--;
        dev_priv->mm.object_memory -= size;
        spin_unlock(&dev_priv->mm.object_stat_lock);
}

static int
i915_gem_wait_for_error(struct i915_gpu_error *error)
{
        int ret;

        might_sleep();

        /*
         * Only wait 10 seconds for the gpu reset to complete to avoid hanging
         * userspace. If it takes that long something really bad is going on and
         * we should simply try to bail out and fail as gracefully as possible.
         */
        ret = wait_event_interruptible_timeout(error->reset_queue,
                                               !i915_reset_backoff(error),
                                               I915_RESET_TIMEOUT);
        if (ret == 0) {
                DRM_ERROR("Timed out waiting for the gpu reset to complete\n");
                return -EIO;
        } else if (ret < 0) {
                return ret;
        } else {
                return 0;
        }
}

int i915_mutex_lock_interruptible(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = to_i915(dev);
        int ret;

        ret = i915_gem_wait_for_error(&dev_priv->gpu_error);
        if (ret)
                return ret;

        ret = mutex_lock_interruptible(&dev->struct_mutex);
        if (ret)
                return ret;

        return 0;
}

int
i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
                            struct drm_file *file)
{
        struct drm_i915_private *dev_priv = to_i915(dev);
        struct i915_ggtt *ggtt = &dev_priv->ggtt;
        struct drm_i915_gem_get_aperture *args = data;
        struct i915_vma *vma;
        u64 pinned;

        pinned = ggtt->base.reserved;
        mutex_lock(&dev->struct_mutex);
        list_for_each_entry(vma, &ggtt->base.active_list, vm_link)
                if (i915_vma_is_pinned(vma))
                        pinned += vma->node.size;
        list_for_each_entry(vma, &ggtt->base.inactive_list, vm_link)
                if (i915_vma_is_pinned(vma))
                        pinned += vma->node.size;
        mutex_unlock(&dev->struct_mutex);

        args->aper_size = ggtt->base.total;
        args->aper_available_size = args->aper_size - pinned;

        return 0;
}

static int i915_gem_object_get_pages_phys(struct drm_i915_gem_object *obj)
{
        struct address_space *mapping = obj->base.filp->f_mapping;
        drm_dma_handle_t *phys;
        struct sg_table *st;
        struct scatterlist *sg;
        char *vaddr;
        int i;
        int err;

        if (WARN_ON(i915_gem_object_needs_bit17_swizzle(obj)))
                return -EINVAL;

        /* Always aligning to the object size, allows a single allocation
         * to handle all possible callers, and given typical object sizes,
         * the alignment of the buddy allocation will naturally match.
         */
        phys = drm_pci_alloc(obj->base.dev,
                             roundup_pow_of_two(obj->base.size),
                             roundup_pow_of_two(obj->base.size));
        if (!phys)
                return -ENOMEM;

        vaddr = phys->vaddr;
        for (i = 0; i < obj->base.size / PAGE_SIZE; i++) {
                struct page *page;
                char *src;

                page = shmem_read_mapping_page(mapping, i);
                if (IS_ERR(page)) {
                        err = PTR_ERR(page);
                        goto err_phys;
                }

                src = kmap_atomic(page);
                memcpy(vaddr, src, PAGE_SIZE);
                drm_clflush_virt_range(vaddr, PAGE_SIZE);
                kunmap_atomic(src);

                put_page(page);
                vaddr += PAGE_SIZE;
        }

        i915_gem_chipset_flush(to_i915(obj->base.dev));

        st = kmalloc(sizeof(*st), GFP_KERNEL);
        if (!st) {
                err = -ENOMEM;
                goto err_phys;
        }

        if (sg_alloc_table(st, 1, GFP_KERNEL)) {
                kfree(st);
                err = -ENOMEM;
                goto err_phys;
        }

        sg = st->sgl;
        sg->offset = 0;
        sg->length = obj->base.size;

        sg_dma_address(sg) = phys->busaddr;
        sg_dma_len(sg) = obj->base.size;

        obj->phys_handle = phys;

        __i915_gem_object_set_pages(obj, st, sg->length);

        return 0;

err_phys:
        drm_pci_free(obj->base.dev, phys);

        return err;
}

static void __start_cpu_write(struct drm_i915_gem_object *obj)
{
        obj->base.read_domains = I915_GEM_DOMAIN_CPU;
        obj->base.write_domain = I915_GEM_DOMAIN_CPU;
        if (cpu_write_needs_clflush(obj))
                obj->cache_dirty = true;
}

static void
__i915_gem_object_release_shmem(struct drm_i915_gem_object *obj,
                                struct sg_table *pages,
                                bool needs_clflush)
{
        GEM_BUG_ON(obj->mm.madv == __I915_MADV_PURGED);

        if (obj->mm.madv == I915_MADV_DONTNEED)
                obj->mm.dirty = false;

        if (needs_clflush &&
            (obj->base.read_domains & I915_GEM_DOMAIN_CPU) == 0 &&
            !(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_READ))
                drm_clflush_sg(pages);

        __start_cpu_write(obj);
}

static void
i915_gem_object_put_pages_phys(struct drm_i915_gem_object *obj,
                               struct sg_table *pages)
{
        __i915_gem_object_release_shmem(obj, pages, false);

        if (obj->mm.dirty) {
                struct address_space *mapping = obj->base.filp->f_mapping;
                char *vaddr = obj->phys_handle->vaddr;
                int i;

                for (i = 0; i < obj->base.size / PAGE_SIZE; i++) {
                        struct page *page;
                        char *dst;

                        page = shmem_read_mapping_page(mapping, i);
                        if (IS_ERR(page))
                                continue;

                        dst = kmap_atomic(page);
                        drm_clflush_virt_range(vaddr, PAGE_SIZE);
                        memcpy(dst, vaddr, PAGE_SIZE);
                        kunmap_atomic(dst);

                        set_page_dirty(page);
                        if (obj->mm.madv == I915_MADV_WILLNEED)
                                mark_page_accessed(page);
                        put_page(page);
                        vaddr += PAGE_SIZE;
                }
                obj->mm.dirty = false;
        }

        sg_free_table(pages);
        kfree(pages);

        drm_pci_free(obj->base.dev, obj->phys_handle);
}

static void
i915_gem_object_release_phys(struct drm_i915_gem_object *obj)
{
        i915_gem_object_unpin_pages(obj);
}

static const struct drm_i915_gem_object_ops i915_gem_phys_ops = {
        .get_pages = i915_gem_object_get_pages_phys,
        .put_pages = i915_gem_object_put_pages_phys,
        .release = i915_gem_object_release_phys,
};

static const struct drm_i915_gem_object_ops i915_gem_object_ops;

int i915_gem_object_unbind(struct drm_i915_gem_object *obj)
{
        struct i915_vma *vma;
        LIST_HEAD(still_in_list);
        int ret;

        lockdep_assert_held(&obj->base.dev->struct_mutex);

        /* Closed vma are removed from the obj->vma_list - but they may
         * still have an active binding on the object. To remove those we
         * must wait for all rendering to complete to the object (as unbinding
         * must anyway), and retire the requests.
         */
        ret = i915_gem_object_set_to_cpu_domain(obj, false);
        if (ret)
                return ret;

        while ((vma = list_first_entry_or_null(&obj->vma_list,
                                               struct i915_vma,
                                               obj_link))) {
                list_move_tail(&vma->obj_link, &still_in_list);
                ret = i915_vma_unbind(vma);
                if (ret)
                        break;
        }
        list_splice(&still_in_list, &obj->vma_list);

        return ret;
}

static long
i915_gem_object_wait_fence(struct dma_fence *fence,
                           unsigned int flags,
                           long timeout,
                           struct intel_rps_client *rps_client)
{
        struct drm_i915_gem_request *rq;

        BUILD_BUG_ON(I915_WAIT_INTERRUPTIBLE != 0x1);

        if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
                return timeout;

        if (!dma_fence_is_i915(fence))
                return dma_fence_wait_timeout(fence,
                                              flags & I915_WAIT_INTERRUPTIBLE,
                                              timeout);

        rq = to_request(fence);
        if (i915_gem_request_completed(rq))
                goto out;

        /* This client is about to stall waiting for the GPU. In many cases
         * this is undesirable and limits the throughput of the system, as
         * many clients cannot continue processing user input/output whilst
         * blocked. RPS autotuning may take tens of milliseconds to respond
         * to the GPU load and thus incurs additional latency for the client.
         * We can circumvent that by promoting the GPU frequency to maximum
         * before we wait. This makes the GPU throttle up much more quickly
         * (good for benchmarks and user experience, e.g. window animations),
         * but at a cost of spending more power processing the workload
         * (bad for battery). Not all clients even want their results
         * immediately and for them we should just let the GPU select its own
         * frequency to maximise efficiency. To prevent a single client from
         * forcing the clocks too high for the whole system, we only allow
         * each client to waitboost once in a busy period.
         */
        if (rps_client) {
                if (INTEL_GEN(rq->i915) >= 6)
                        gen6_rps_boost(rq, rps_client);
                else
                        rps_client = NULL;
        }

        timeout = i915_wait_request(rq, flags, timeout);

out:
        if (flags & I915_WAIT_LOCKED && i915_gem_request_completed(rq))
                i915_gem_request_retire_upto(rq);

        return timeout;
}

static long
i915_gem_object_wait_reservation(struct reservation_object *resv,
                                 unsigned int flags,
                                 long timeout,
                                 struct intel_rps_client *rps_client)
{
        unsigned int seq = __read_seqcount_begin(&resv->seq);
        struct dma_fence *excl;
        bool prune_fences = false;

        if (flags & I915_WAIT_ALL) {
                struct dma_fence **shared;
                unsigned int count, i;
                int ret;

                ret = reservation_object_get_fences_rcu(resv,
                                                        &excl, &count, &shared);
                if (ret)
                        return ret;

                for (i = 0; i < count; i++) {
                        timeout = i915_gem_object_wait_fence(shared[i],
                                                             flags, timeout,
                                                             rps_client);
                        if (timeout < 0)
                                break;

                        dma_fence_put(shared[i]);
                }

                for (; i < count; i++)
                        dma_fence_put(shared[i]);
                kfree(shared);

                prune_fences = count && timeout >= 0;
        } else {
                excl = reservation_object_get_excl_rcu(resv);
        }

        if (excl && timeout >= 0) {
                timeout = i915_gem_object_wait_fence(excl, flags, timeout,
                                                     rps_client);
                prune_fences = timeout >= 0;
        }

        dma_fence_put(excl);

        /* Oportunistically prune the fences iff we know they have *all* been
         * signaled and that the reservation object has not been changed (i.e.
         * no new fences have been added).
         */
        if (prune_fences && !__read_seqcount_retry(&resv->seq, seq)) {
                if (reservation_object_trylock(resv)) {
                        if (!__read_seqcount_retry(&resv->seq, seq))
                                reservation_object_add_excl_fence(resv, NULL);
                        reservation_object_unlock(resv);
                }
        }

        return timeout;
}

static void __fence_set_priority(struct dma_fence *fence, int prio)
{
        struct drm_i915_gem_request *rq;
        struct intel_engine_cs *engine;

        if (!dma_fence_is_i915(fence))
                return;

        rq = to_request(fence);
        engine = rq->engine;
        if (!engine->schedule)
                return;

        engine->schedule(rq, prio);
}

static void fence_set_priority(struct dma_fence *fence, int prio)
{
        /* Recurse once into a fence-array */
        if (dma_fence_is_array(fence)) {
                struct dma_fence_array *array = to_dma_fence_array(fence);
                int i;

                for (i = 0; i < array->num_fences; i++)
                        __fence_set_priority(array->fences[i], prio);
        } else {
                __fence_set_priority(fence, prio);
        }
}

int
i915_gem_object_wait_priority(struct drm_i915_gem_object *obj,
                              unsigned int flags,
                              int prio)
{
        struct dma_fence *excl;

        if (flags & I915_WAIT_ALL) {
                struct dma_fence **shared;
                unsigned int count, i;
                int ret;

                ret = reservation_object_get_fences_rcu(obj->resv,
                                                        &excl, &count, &shared);
                if (ret)
                        return ret;

                for (i = 0; i < count; i++) {
                        fence_set_priority(shared[i], prio);
                        dma_fence_put(shared[i]);
                }

                kfree(shared);
        } else {
                excl = reservation_object_get_excl_rcu(obj->resv);
        }

        if (excl) {
                fence_set_priority(excl, prio);
                dma_fence_put(excl);
        }
        return 0;
}

/**
 * Waits for rendering to the object to be completed
 * @obj: i915 gem object
 * @flags: how to wait (under a lock, for all rendering or just for writes etc)
 * @timeout: how long to wait
 * @rps: client (user process) to charge for any waitboosting
 */
int
i915_gem_object_wait(struct drm_i915_gem_object *obj,
                     unsigned int flags,
                     long timeout,
                     struct intel_rps_client *rps_client)
{
        might_sleep();
#if IS_ENABLED(CONFIG_LOCKDEP)
        GEM_BUG_ON(debug_locks &&
                   !!lockdep_is_held(&obj->base.dev->struct_mutex) !=
                   !!(flags & I915_WAIT_LOCKED));
#endif
        GEM_BUG_ON(timeout < 0);

        timeout = i915_gem_object_wait_reservation(obj->resv,
                                                   flags, timeout,
                                                   rps_client);
        return timeout < 0 ? timeout : 0;
}

static struct intel_rps_client *to_rps_client(struct drm_file *file)
{
        struct drm_i915_file_private *fpriv = file->driver_priv;

        return &fpriv->rps_client;
}

static int
i915_gem_phys_pwrite(struct drm_i915_gem_object *obj,
                     struct drm_i915_gem_pwrite *args,
                     struct drm_file *file)
{
        void *vaddr = obj->phys_handle->vaddr + args->offset;
        char __user *user_data = u64_to_user_ptr(args->data_ptr);

        /* We manually control the domain here and pretend that it
         * remains coherent i.e. in the GTT domain, like shmem_pwrite.
         */
        intel_fb_obj_invalidate(obj, ORIGIN_CPU);
        if (copy_from_user(vaddr, user_data, args->size))
                return -EFAULT;

        drm_clflush_virt_range(vaddr, args->size);
        i915_gem_chipset_flush(to_i915(obj->base.dev));

        intel_fb_obj_flush(obj, ORIGIN_CPU);
        return 0;
}

void *i915_gem_object_alloc(struct drm_i915_private *dev_priv)
{
        return kmem_cache_zalloc(dev_priv->objects, GFP_KERNEL);
}

void i915_gem_object_free(struct drm_i915_gem_object *obj)
{
        struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
        kmem_cache_free(dev_priv->objects, obj);
}

static int
i915_gem_create(struct drm_file *file,
                struct drm_i915_private *dev_priv,
                uint64_t size,
                uint32_t *handle_p)
{
        struct drm_i915_gem_object *obj;
        int ret;
        u32 handle;

        size = roundup(size, PAGE_SIZE);
        if (size == 0)
                return -EINVAL;

        /* Allocate the new object */
        obj = i915_gem_object_create(dev_priv, size);
        if (IS_ERR(obj))
                return PTR_ERR(obj);

        ret = drm_gem_handle_create(file, &obj->base, &handle);
        /* drop reference from allocate - handle holds it now */
        i915_gem_object_put(obj);
        if (ret)
                return ret;

        *handle_p = handle;
        return 0;
}

int
i915_gem_dumb_create(struct drm_file *file,
                     struct drm_device *dev,
                     struct drm_mode_create_dumb *args)
{
        /* have to work out size/pitch and return them */
        args->pitch = ALIGN(args->width * DIV_ROUND_UP(args->bpp, 8), 64);
        args->size = args->pitch * args->height;
        return i915_gem_create(file, to_i915(dev),
                               args->size, &args->handle);
}

static bool gpu_write_needs_clflush(struct drm_i915_gem_object *obj)
{
        return !(obj->cache_level == I915_CACHE_NONE ||
                 obj->cache_level == I915_CACHE_WT);
}

/**
 * Creates a new mm object and returns a handle to it.
 * @dev: drm device pointer
 * @data: ioctl data blob
 * @file: drm file pointer
 */
int
i915_gem_create_ioctl(struct drm_device *dev, void *data,
                      struct drm_file *file)
{
        struct drm_i915_private *dev_priv = to_i915(dev);
        struct drm_i915_gem_create *args = data;

        i915_gem_flush_free_objects(dev_priv);

        return i915_gem_create(file, dev_priv,
                               args->size, &args->handle);
}

static inline enum fb_op_origin
fb_write_origin(struct drm_i915_gem_object *obj, unsigned int domain)
{
        return (domain == I915_GEM_DOMAIN_GTT ?
                obj->frontbuffer_ggtt_origin : ORIGIN_CPU);
}

static void
flush_write_domain(struct drm_i915_gem_object *obj, unsigned int flush_domains)
{
        struct drm_i915_private *dev_priv = to_i915(obj->base.dev);

        if (!(obj->base.write_domain & flush_domains))
                return;

        /* No actual flushing is required for the GTT write domain.  Writes
         * to it "immediately" go to main memory as far as we know, so there's
         * no chipset flush.  It also doesn't land in render cache.
         *
         * However, we do have to enforce the order so that all writes through
         * the GTT land before any writes to the device, such as updates to
         * the GATT itself.
         *
         * We also have to wait a bit for the writes to land from the GTT.
         * An uncached read (i.e. mmio) seems to be ideal for the round-trip
         * timing. This issue has only been observed when switching quickly
         * between GTT writes and CPU reads from inside the kernel on recent hw,
         * and it appears to only affect discrete GTT blocks (i.e. on LLC
         * system agents we cannot reproduce this behaviour).
         */
        wmb();

        switch (obj->base.write_domain) {
        case I915_GEM_DOMAIN_GTT:
                if (!HAS_LLC(dev_priv)) {
                        intel_runtime_pm_get(dev_priv);
                        spin_lock_irq(&dev_priv->uncore.lock);
                        POSTING_READ_FW(RING_HEAD(dev_priv->engine[RCS]->mmio_base));
                        spin_unlock_irq(&dev_priv->uncore.lock);
                        intel_runtime_pm_put(dev_priv);
                }

                intel_fb_obj_flush(obj,
                                   fb_write_origin(obj, I915_GEM_DOMAIN_GTT));
                break;

        case I915_GEM_DOMAIN_CPU:
                i915_gem_clflush_object(obj, I915_CLFLUSH_SYNC);
                break;

        case I915_GEM_DOMAIN_RENDER:
                if (gpu_write_needs_clflush(obj))
                        obj->cache_dirty = true;
                break;
        }

        obj->base.write_domain = 0;
}

static inline int
__copy_to_user_swizzled(char __user *cpu_vaddr,
                        const char *gpu_vaddr, int gpu_offset,
                        int length)
{
        int ret, cpu_offset = 0;

        while (length > 0) {
                int cacheline_end = ALIGN(gpu_offset + 1, 64);
                int this_length = min(cacheline_end - gpu_offset, length);
                int swizzled_gpu_offset = gpu_offset ^ 64;

                ret = __copy_to_user(cpu_vaddr + cpu_offset,
                                     gpu_vaddr + swizzled_gpu_offset,
                                     this_length);
                if (ret)
                        return ret + length;

                cpu_offset += this_length;
                gpu_offset += this_length;
                length -= this_length;
        }

        return 0;
}

static inline int
__copy_from_user_swizzled(char *gpu_vaddr, int gpu_offset,
                          const char __user *cpu_vaddr,
                          int length)
{
        int ret, cpu_offset = 0;

        while (length > 0) {
                int cacheline_end = ALIGN(gpu_offset + 1, 64);
                int this_length = min(cacheline_end - gpu_offset, length);
                int swizzled_gpu_offset = gpu_offset ^ 64;

                ret = __copy_from_user(gpu_vaddr + swizzled_gpu_offset,
                                       cpu_vaddr + cpu_offset,
                                       this_length);
                if (ret)
                        return ret + length;

                cpu_offset += this_length;
                gpu_offset += this_length;
                length -= this_length;
        }

        return 0;
}

/*
 * Pins the specified object's pages and synchronizes the object with
 * GPU accesses. Sets needs_clflush to non-zero if the caller should
 * flush the object from the CPU cache.
 */
int i915_gem_obj_prepare_shmem_read(struct drm_i915_gem_object *obj,
                                    unsigned int *needs_clflush)
{
        int ret;

        lockdep_assert_held(&obj->base.dev->struct_mutex);

        *needs_clflush = 0;
        if (!i915_gem_object_has_struct_page(obj))
                return -ENODEV;

        ret = i915_gem_object_wait(obj,
                                   I915_WAIT_INTERRUPTIBLE |
                                   I915_WAIT_LOCKED,
                                   MAX_SCHEDULE_TIMEOUT,
                                   NULL);
        if (ret)
                return ret;

        ret = i915_gem_object_pin_pages(obj);
        if (ret)
                return ret;

        if (obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_READ ||
            !static_cpu_has(X86_FEATURE_CLFLUSH)) {
                ret = i915_gem_object_set_to_cpu_domain(obj, false);
                if (ret)
                        goto err_unpin;
                else
                        goto out;
        }

        flush_write_domain(obj, ~I915_GEM_DOMAIN_CPU);

        /* If we're not in the cpu read domain, set ourself into the gtt
         * read domain and manually flush cachelines (if required). This
         * optimizes for the case when the gpu will dirty the data
         * anyway again before the next pread happens.
         */
        if (!obj->cache_dirty &&
            !(obj->base.read_domains & I915_GEM_DOMAIN_CPU))
                *needs_clflush = CLFLUSH_BEFORE;

out:
        /* return with the pages pinned */
        return 0;

err_unpin:
        i915_gem_object_unpin_pages(obj);
        return ret;
}

int i915_gem_obj_prepare_shmem_write(struct drm_i915_gem_object *obj,
                                     unsigned int *needs_clflush)
{
        int ret;

        lockdep_assert_held(&obj->base.dev->struct_mutex);

        *needs_clflush = 0;
        if (!i915_gem_object_has_struct_page(obj))
                return -ENODEV;

        ret = i915_gem_object_wait(obj,
                                   I915_WAIT_INTERRUPTIBLE |
                                   I915_WAIT_LOCKED |
                                   I915_WAIT_ALL,
                                   MAX_SCHEDULE_TIMEOUT,
                                   NULL);
        if (ret)
                return ret;

        ret = i915_gem_object_pin_pages(obj);
        if (ret)
                return ret;

        if (obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE ||
            !static_cpu_has(X86_FEATURE_CLFLUSH)) {
                ret = i915_gem_object_set_to_cpu_domain(obj, true);
                if (ret)
                        goto err_unpin;
                else
                        goto out;
        }

        flush_write_domain(obj, ~I915_GEM_DOMAIN_CPU);

        /* If we're not in the cpu write domain, set ourself into the
         * gtt write domain and manually flush cachelines (as required).
         * This optimizes for the case when the gpu will use the data
         * right away and we therefore have to clflush anyway.
         */
        if (!obj->cache_dirty) {
                *needs_clflush |= CLFLUSH_AFTER;

                /*
                 * Same trick applies to invalidate partially written
                 * cachelines read before writing.
                 */
                if (!(obj->base.read_domains & I915_GEM_DOMAIN_CPU))
                        *needs_clflush |= CLFLUSH_BEFORE;
        }

out:
        intel_fb_obj_invalidate(obj, ORIGIN_CPU);
        obj->mm.dirty = true;
        /* return with the pages pinned */
        return 0;

err_unpin:
        i915_gem_object_unpin_pages(obj);
        return ret;
}

static void
shmem_clflush_swizzled_range(char *addr, unsigned long length,
                             bool swizzled)
{
        if (unlikely(swizzled)) {
                unsigned long start = (unsigned long) addr;
                unsigned long end = (unsigned long) addr + length;

                /* For swizzling simply ensure that we always flush both
                 * channels. Lame, but simple and it works. Swizzled
                 * pwrite/pread is far from a hotpath - current userspace
                 * doesn't use it at all. */
                start = round_down(start, 128);
                end = round_up(end, 128);

                drm_clflush_virt_range((void *)start, end - start);
        } else {
                drm_clflush_virt_range(addr, length);
        }

}

/* Only difference to the fast-path function is that this can handle bit17
 * and uses non-atomic copy and kmap functions. */
static int
shmem_pread_slow(struct page *page, int offset, int length,
                 char __user *user_data,
                 bool page_do_bit17_swizzling, bool needs_clflush)
{
        char *vaddr;
        int ret;

        vaddr = kmap(page);
        if (needs_clflush)
                shmem_clflush_swizzled_range(vaddr + offset, length,
                                             page_do_bit17_swizzling);

        if (page_do_bit17_swizzling)
                ret = __copy_to_user_swizzled(user_data, vaddr, offset, length);
        else
                ret = __copy_to_user(user_data, vaddr + offset, length);
        kunmap(page);

        return ret ? - EFAULT : 0;
}

static int
shmem_pread(struct page *page, int offset, int length, char __user *user_data,
            bool page_do_bit17_swizzling, bool needs_clflush)
{
        int ret;

        ret = -ENODEV;
        if (!page_do_bit17_swizzling) {
                char *vaddr = kmap_atomic(page);

                if (needs_clflush)
                        drm_clflush_virt_range(vaddr + offset, length);
                ret = __copy_to_user_inatomic(user_data, vaddr + offset, length);
                kunmap_atomic(vaddr);
        }
        if (ret == 0)
                return 0;

        return shmem_pread_slow(page, offset, length, user_data,
                                page_do_bit17_swizzling, needs_clflush);
}

static int
i915_gem_shmem_pread(struct drm_i915_gem_object *obj,
                     struct drm_i915_gem_pread *args)
{
        char __user *user_data;
        u64 remain;
        unsigned int obj_do_bit17_swizzling;
        unsigned int needs_clflush;
        unsigned int idx, offset;
        int ret;

        obj_do_bit17_swizzling = 0;
        if (i915_gem_object_needs_bit17_swizzle(obj))
                obj_do_bit17_swizzling = BIT(17);

        ret = mutex_lock_interruptible(&obj->base.dev->struct_mutex);
        if (ret)
                return ret;

        ret = i915_gem_obj_prepare_shmem_read(obj, &needs_clflush);
        mutex_unlock(&obj->base.dev->struct_mutex);
        if (ret)
                return ret;

        remain = args->size;
        user_data = u64_to_user_ptr(args->data_ptr);
        offset = offset_in_page(args->offset);
        for (idx = args->offset >> PAGE_SHIFT; remain; idx++) {
                struct page *page = i915_gem_object_get_page(obj, idx);
                int length;

                length = remain;
                if (offset + length > PAGE_SIZE)
                        length = PAGE_SIZE - offset;

                ret = shmem_pread(page, offset, length, user_data,
                                  page_to_phys(page) & obj_do_bit17_swizzling,
                                  needs_clflush);
                if (ret)
                        break;

                remain -= length;
                user_data += length;
                offset = 0;
        }

        i915_gem_obj_finish_shmem_access(obj);
        return ret;
}

static inline bool
gtt_user_read(struct io_mapping *mapping,
              loff_t base, int offset,
              char __user *user_data, int length)
{
        void __iomem *vaddr;
        unsigned long unwritten;

        /* We can use the cpu mem copy function because this is X86. */
        vaddr = io_mapping_map_atomic_wc(mapping, base);
        unwritten = __copy_to_user_inatomic(user_data,
                                            (void __force *)vaddr + offset,
                                            length);
        io_mapping_unmap_atomic(vaddr);
        if (unwritten) {
                vaddr = io_mapping_map_wc(mapping, base, PAGE_SIZE);
                unwritten = copy_to_user(user_data,
                                         (void __force *)vaddr + offset,
                                         length);
                io_mapping_unmap(vaddr);
        }
        return unwritten;
}

static int
i915_gem_gtt_pread(struct drm_i915_gem_object *obj,
                   const struct drm_i915_gem_pread *args)
{
        struct drm_i915_private *i915 = to_i915(obj->base.dev);
        struct i915_ggtt *ggtt = &i915->ggtt;
        struct drm_mm_node node;
        struct i915_vma *vma;
        void __user *user_data;
        u64 remain, offset;
        int ret;

        ret = mutex_lock_interruptible(&i915->drm.struct_mutex);
        if (ret)
                return ret;

        intel_runtime_pm_get(i915);
        vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,
                                       PIN_MAPPABLE |
                                       PIN_NONFAULT |
                                       PIN_NONBLOCK);
        if (!IS_ERR(vma)) {
                node.start = i915_ggtt_offset(vma);
                node.allocated = false;
                ret = i915_vma_put_fence(vma);
                if (ret) {
                        i915_vma_unpin(vma);
                        vma = ERR_PTR(ret);
                }
        }
        if (IS_ERR(vma)) {
                ret = insert_mappable_node(ggtt, &node, PAGE_SIZE);
                if (ret)
                        goto out_unlock;
                GEM_BUG_ON(!node.allocated);
        }

        ret = i915_gem_object_set_to_gtt_domain(obj, false);
        if (ret)
                goto out_unpin;

        mutex_unlock(&i915->drm.struct_mutex);

        user_data = u64_to_user_ptr(args->data_ptr);
        remain = args->size;
        offset = args->offset;

        while (remain > 0) {
                /* Operation in this page
                 *
                 * page_base = page offset within aperture
                 * page_offset = offset within page
                 * page_length = bytes to copy for this page
                 */
                u32 page_base = node.start;
                unsigned page_offset = offset_in_page(offset);
                unsigned page_length = PAGE_SIZE - page_offset;
                page_length = remain < page_length ? remain : page_length;
                if (node.allocated) {
                        wmb();
                        ggtt->base.insert_page(&ggtt->base,
                                               i915_gem_object_get_dma_address(obj, offset >> PAGE_SHIFT),
                                               node.start, I915_CACHE_NONE, 0);
                        wmb();
                } else {
                        page_base += offset & PAGE_MASK;
                }

                if (gtt_user_read(&ggtt->mappable, page_base, page_offset,
                                  user_data, page_length)) {
                        ret = -EFAULT;
                        break;
                }

                remain -= page_length;
                user_data += page_length;
                offset += page_length;
        }

        mutex_lock(&i915->drm.struct_mutex);
out_unpin:
        if (node.allocated) {
                wmb();
                ggtt->base.clear_range(&ggtt->base,
                                       node.start, node.size);
                remove_mappable_node(&node);
        } else {
                i915_vma_unpin(vma);
        }
out_unlock:
        intel_runtime_pm_put(i915);
        mutex_unlock(&i915->drm.struct_mutex);

        return ret;
}

/**
 * Reads data from the object referenced by handle.
 * @dev: drm device pointer
 * @data: ioctl data blob
 * @file: drm file pointer
 *
 * On error, the contents of *data are undefined.
 */
int
i915_gem_pread_ioctl(struct drm_device *dev, void *data,
                     struct drm_file *file)
{
        struct drm_i915_gem_pread *args = data;
        struct drm_i915_gem_object *obj;
        int ret;

        if (args->size == 0)
                return 0;

        if (!access_ok(VERIFY_WRITE,
                       u64_to_user_ptr(args->data_ptr),
                       args->size))
                return -EFAULT;

        obj = i915_gem_object_lookup(file, args->handle);
        if (!obj)
                return -ENOENT;

        /* Bounds check source.  */
        if (range_overflows_t(u64, args->offset, args->size, obj->base.size)) {
                ret = -EINVAL;
                goto out;
        }

        trace_i915_gem_object_pread(obj, args->offset, args->size);

        ret = i915_gem_object_wait(obj,
                                   I915_WAIT_INTERRUPTIBLE,
                                   MAX_SCHEDULE_TIMEOUT,
                                   to_rps_client(file));
        if (ret)
                goto out;

        ret = i915_gem_object_pin_pages(obj);
        if (ret)
                goto out;

        ret = i915_gem_shmem_pread(obj, args);
        if (ret == -EFAULT || ret == -ENODEV)
                ret = i915_gem_gtt_pread(obj, args);

        i915_gem_object_unpin_pages(obj);
out:
        i915_gem_object_put(obj);
        return ret;
}

/* This is the fast write path which cannot handle
 * page faults in the source data
 */

static inline bool
ggtt_write(struct io_mapping *mapping,
           loff_t base, int offset,
           char __user *user_data, int length)
{
        void __iomem *vaddr;
        unsigned long unwritten;

        /* We can use the cpu mem copy function because this is X86. */
        vaddr = io_mapping_map_atomic_wc(mapping, base);
        unwritten = __copy_from_user_inatomic_nocache((void __force *)vaddr + offset,
                                                      user_data, length);
        io_mapping_unmap_atomic(vaddr);
        if (unwritten) {
                vaddr = io_mapping_map_wc(mapping, base, PAGE_SIZE);
                unwritten = copy_from_user((void __force *)vaddr + offset,
                                           user_data, length);
                io_mapping_unmap(vaddr);
        }

        return unwritten;
}

/**
 * This is the fast pwrite path, where we copy the data directly from the
 * user into the GTT, uncached.
 * @obj: i915 GEM object
 * @args: pwrite arguments structure
 */
static int
i915_gem_gtt_pwrite_fast(struct drm_i915_gem_object *obj,
                         const struct drm_i915_gem_pwrite *args)
{
        struct drm_i915_private *i915 = to_i915(obj->base.dev);
        struct i915_ggtt *ggtt = &i915->ggtt;
        struct drm_mm_node node;
        struct i915_vma *vma;
        u64 remain, offset;
        void __user *user_data;
        int ret;

        ret = mutex_lock_interruptible(&i915->drm.struct_mutex);
        if (ret)
                return ret;

        if (i915_gem_object_has_struct_page(obj)) {
                /*
                 * Avoid waking the device up if we can fallback, as
                 * waking/resuming is very slow (worst-case 10-100 ms
                 * depending on PCI sleeps and our own resume time).
                 * This easily dwarfs any performance advantage from
                 * using the cache bypass of indirect GGTT access.
                 */
                if (!intel_runtime_pm_get_if_in_use(i915)) {
                        ret = -EFAULT;
                        goto out_unlock;
                }
        } else {
                /* No backing pages, no fallback, we must force GGTT access */
                intel_runtime_pm_get(i915);
        }

        vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,
                                       PIN_MAPPABLE |
                                       PIN_NONFAULT |
                                       PIN_NONBLOCK);
        if (!IS_ERR(vma)) {
                node.start = i915_ggtt_offset(vma);
                node.allocated = false;
                ret = i915_vma_put_fence(vma);
                if (ret) {
                        i915_vma_unpin(vma);
                        vma = ERR_PTR(ret);
                }
        }
        if (IS_ERR(vma)) {
                ret = insert_mappable_node(ggtt, &node, PAGE_SIZE);
                if (ret)
                        goto out_rpm;
                GEM_BUG_ON(!node.allocated);
        }

        ret = i915_gem_object_set_to_gtt_domain(obj, true);
        if (ret)
                goto out_unpin;

        mutex_unlock(&i915->drm.struct_mutex);

        intel_fb_obj_invalidate(obj, ORIGIN_CPU);

        user_data = u64_to_user_ptr(args->data_ptr);
        offset = args->offset;
        remain = args->size;
        while (remain) {
                /* Operation in this page
                 *
                 * page_base = page offset within aperture
                 * page_offset = offset within page
                 * page_length = bytes to copy for this page
                 */
                u32 page_base = node.start;
                unsigned int page_offset = offset_in_page(offset);
                unsigned int page_length = PAGE_SIZE - page_offset;
                page_length = remain < page_length ? remain : page_length;
                if (node.allocated) {
                        wmb(); /* flush the write before we modify the GGTT */
                        ggtt->base.insert_page(&ggtt->base,
                                               i915_gem_object_get_dma_address(obj, offset >> PAGE_SHIFT),
                                               node.start, I915_CACHE_NONE, 0);
                        wmb(); /* flush modifications to the GGTT (insert_page) */
                } else {
                        page_base += offset & PAGE_MASK;
                }
                /* If we get a fault while copying data, then (presumably) our
                 * source page isn't available.  Return the error and we'll
                 * retry in the slow path.
                 * If the object is non-shmem backed, we retry again with the
                 * path that handles page fault.
                 */
                if (ggtt_write(&ggtt->mappable, page_base, page_offset,
                               user_data, page_length)) {
                        ret = -EFAULT;
                        break;
                }

                remain -= page_length;
                user_data += page_length;
                offset += page_length;
        }
        intel_fb_obj_flush(obj, ORIGIN_CPU);

        mutex_lock(&i915->drm.struct_mutex);
out_unpin:
        if (node.allocated) {
                wmb();
                ggtt->base.clear_range(&ggtt->base,
                                       node.start, node.size);
                remove_mappable_node(&node);
        } else {
                i915_vma_unpin(vma);
        }
out_rpm:
        intel_runtime_pm_put(i915);
out_unlock:
        mutex_unlock(&i915->drm.struct_mutex);
        return ret;
}

static int
shmem_pwrite_slow(struct page *page, int offset, int length,
                  char __user *user_data,
                  bool page_do_bit17_swizzling,
                  bool needs_clflush_before,
                  bool needs_clflush_after)
{
        char *vaddr;
        int ret;

        vaddr = kmap(page);
        if (unlikely(needs_clflush_before || page_do_bit17_swizzling))
                shmem_clflush_swizzled_range(vaddr + offset, length,
                                             page_do_bit17_swizzling);
        if (page_do_bit17_swizzling)
                ret = __copy_from_user_swizzled(vaddr, offset, user_data,
                                                length);
        else
                ret = __copy_from_user(vaddr + offset, user_data, length);
        if (needs_clflush_after)
                shmem_clflush_swizzled_range(vaddr + offset, length,
                                             page_do_bit17_swizzling);
        kunmap(page);

        return ret ? -EFAULT : 0;
}

/* Per-page copy function for the shmem pwrite fastpath.
 * Flushes invalid cachelines before writing to the target if
 * needs_clflush_before is set and flushes out any written cachelines after
 * writing if needs_clflush is set.
 */
static int
shmem_pwrite(struct page *page, int offset, int len, char __user *user_data,
             bool page_do_bit17_swizzling,
             bool needs_clflush_before,
             bool needs_clflush_after)
{
        int ret;

        ret = -ENODEV;
        if (!page_do_bit17_swizzling) {
                char *vaddr = kmap_atomic(page);

                if (needs_clflush_before)
                        drm_clflush_virt_range(vaddr + offset, len);
                ret = __copy_from_user_inatomic(vaddr + offset, user_data, len);
                if (needs_clflush_after)
                        drm_clflush_virt_range(vaddr + offset, len);

                kunmap_atomic(vaddr);
        }
        if (ret == 0)
                return ret;

        return shmem_pwrite_slow(page, offset, len, user_data,
                                 page_do_bit17_swizzling,
                                 needs_clflush_before,
                                 needs_clflush_after);
}

static int
i915_gem_shmem_pwrite(struct drm_i915_gem_object *obj,
                      const struct drm_i915_gem_pwrite *args)
{
        struct drm_i915_private *i915 = to_i915(obj->base.dev);
        void __user *user_data;
        u64 remain;
        unsigned int obj_do_bit17_swizzling;
        unsigned int partial_cacheline_write;
        unsigned int needs_clflush;
        unsigned int offset, idx;
        int ret;

        ret = mutex_lock_interruptible(&i915->drm.struct_mutex);
        if (ret)
                return ret;

        ret = i915_gem_obj_prepare_shmem_write(obj, &needs_clflush);
        mutex_unlock(&i915->drm.struct_mutex);
        if (ret)
                return ret;

        obj_do_bit17_swizzling = 0;
        if (i915_gem_object_needs_bit17_swizzle(obj))
                obj_do_bit17_swizzling = BIT(17);

        /* If we don't overwrite a cacheline completely we need to be
         * careful to have up-to-date data by first clflushing. Don't
         * overcomplicate things and flush the entire patch.
         */
        partial_cacheline_write = 0;
        if (needs_clflush & CLFLUSH_BEFORE)
                partial_cacheline_write = boot_cpu_data.x86_clflush_size - 1;

        user_data = u64_to_user_ptr(args->data_ptr);
        remain = args->size;
        offset = offset_in_page(args->offset);
        for (idx = args->offset >> PAGE_SHIFT; remain; idx++) {
                struct page *page = i915_gem_object_get_page(obj, idx);
                int length;

                length = remain;
                if (offset + length > PAGE_SIZE)
                        length = PAGE_SIZE - offset;

                ret = shmem_pwrite(page, offset, length, user_data,
                                   page_to_phys(page) & obj_do_bit17_swizzling,
                                   (offset | length) & partial_cacheline_write,
                                   needs_clflush & CLFLUSH_AFTER);
                if (ret)
                        break;

                remain -= length;
                user_data += length;
                offset = 0;
        }

        intel_fb_obj_flush(obj, ORIGIN_CPU);
        i915_gem_obj_finish_shmem_access(obj);
        return ret;
}

/**
 * Writes data to the object referenced by handle.
 * @dev: drm device
 * @data: ioctl data blob
 * @file: drm file
 *
 * On error, the contents of the buffer that were to be modified are undefined.
 */
int
i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
                      struct drm_file *file)
{
        struct drm_i915_gem_pwrite *args = data;
        struct drm_i915_gem_object *obj;
        int ret;

        if (args->size == 0)
                return 0;

        if (!access_ok(VERIFY_READ,
                       u64_to_user_ptr(args->data_ptr),
                       args->size))
                return -EFAULT;

        obj = i915_gem_object_lookup(file, args->handle);
        if (!obj)
                return -ENOENT;

        /* Bounds check destination. */
        if (range_overflows_t(u64, args->offset, args->size, obj->base.size)) {
                ret = -EINVAL;
                goto err;
        }

        trace_i915_gem_object_pwrite(obj, args->offset, args->size);

        ret = -ENODEV;
        if (obj->ops->pwrite)
                ret = obj->ops->pwrite(obj, args);
        if (ret != -ENODEV)
                goto err;

        ret = i915_gem_object_wait(obj,
                                   I915_WAIT_INTERRUPTIBLE |
                                   I915_WAIT_ALL,
                                   MAX_SCHEDULE_TIMEOUT,
                                   to_rps_client(file));
        if (ret)
                goto err;

        ret = i915_gem_object_pin_pages(obj);
        if (ret)
                goto err;

        ret = -EFAULT;
        /* We can only do the GTT pwrite on untiled buffers, as otherwise
         * it would end up going through the fenced access, and we'll get
         * different detiling behavior between reading and writing.
         * pread/pwrite currently are reading and writing from the CPU
         * perspective, requiring manual detiling by the client.
         */
        if (!i915_gem_object_has_struct_page(obj) ||
            cpu_write_needs_clflush(obj))
                /* Note that the gtt paths might fail with non-page-backed user
                 * pointers (e.g. gtt mappings when moving data between
                 * textures). Fallback to the shmem path in that case.
                 */
                ret = i915_gem_gtt_pwrite_fast(obj, args);

        if (ret == -EFAULT || ret == -ENOSPC) {
                if (obj->phys_handle)
                        ret = i915_gem_phys_pwrite(obj, args, file);
                else
                        ret = i915_gem_shmem_pwrite(obj, args);
        }

        i915_gem_object_unpin_pages(obj);
err:
        i915_gem_object_put(obj);
        return ret;
}

static void i915_gem_object_bump_inactive_ggtt(struct drm_i915_gem_object *obj)
{
        struct drm_i915_private *i915;
        struct list_head *list;
        struct i915_vma *vma;

        GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));

        list_for_each_entry(vma, &obj->vma_list, obj_link) {
                if (!i915_vma_is_ggtt(vma))
                        break;

                if (i915_vma_is_active(vma))
                        continue;

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

                list_move_tail(&vma->vm_link, &vma->vm->inactive_list);
        }

        i915 = to_i915(obj->base.dev);
        spin_lock(&i915->mm.obj_lock);
        list = obj->bind_count ? &i915->mm.bound_list : &i915->mm.unbound_list;
        list_move_tail(&obj->mm.link, list);
        spin_unlock(&i915->mm.obj_lock);
}

/**
 * Called when user space prepares to use an object with the CPU, either
 * through the mmap ioctl's mapping or a GTT mapping.
 * @dev: drm device
 * @data: ioctl data blob
 * @file: drm file
 */
int
i915_gem_set_domain_ioctl(struct drm_device *dev, void *data,
                          struct drm_file *file)
{
        struct drm_i915_gem_set_domain *args = data;
        struct drm_i915_gem_object *obj;
        uint32_t read_domains = args->read_domains;
        uint32_t write_domain = args->write_domain;
        int err;

        /* Only handle setting domains to types used by the CPU. */
        if ((write_domain | read_domains) & I915_GEM_GPU_DOMAINS)
                return -EINVAL;

        /* Having something in the write domain implies it's in the read
         * domain, and only that read domain.  Enforce that in the request.
         */
        if (write_domain != 0 && read_domains != write_domain)
                return -EINVAL;

        obj = i915_gem_object_lookup(file, args->handle);
        if (!obj)
                return -ENOENT;

        /* Try to flush the object off the GPU without holding the lock.
         * We will repeat the flush holding the lock in the normal manner
         * to catch cases where we are gazumped.
         */
        err = i915_gem_object_wait(obj,
                                   I915_WAIT_INTERRUPTIBLE |
                                   (write_domain ? I915_WAIT_ALL : 0),
                                   MAX_SCHEDULE_TIMEOUT,
                                   to_rps_client(file));
        if (err)
                goto out;

        /* Flush and acquire obj->pages so that we are coherent through
         * direct access in memory with previous cached writes through
         * shmemfs and that our cache domain tracking remains valid.
         * For example, if the obj->filp was moved to swap without us
         * being notified and releasing the pages, we would mistakenly
         * continue to assume that the obj remained out of the CPU cached
         * domain.
         */
        err = i915_gem_object_pin_pages(obj);
        if (err)
                goto out;

        err = i915_mutex_lock_interruptible(dev);
        if (err)
                goto out_unpin;

        if (read_domains & I915_GEM_DOMAIN_WC)
                err = i915_gem_object_set_to_wc_domain(obj, write_domain);
        else if (read_domains & I915_GEM_DOMAIN_GTT)
                err = i915_gem_object_set_to_gtt_domain(obj, write_domain);
        else
                err = i915_gem_object_set_to_cpu_domain(obj, write_domain);

        /* And bump the LRU for this access */
        i915_gem_object_bump_inactive_ggtt(obj);

        mutex_unlock(&dev->struct_mutex);

        if (write_domain != 0)
                intel_fb_obj_invalidate(obj,
                                        fb_write_origin(obj, write_domain));

out_unpin:
        i915_gem_object_unpin_pages(obj);
out:
        i915_gem_object_put(obj);
        return err;
}

/**
 * Called when user space has done writes to this buffer
 * @dev: drm device
 * @data: ioctl data blob
 * @file: drm file
 */
int
i915_gem_sw_finish_ioctl(struct drm_device *dev, void *data,
                         struct drm_file *file)
{
        struct drm_i915_gem_sw_finish *args = data;
        struct drm_i915_gem_object *obj;

        obj = i915_gem_object_lookup(file, args->handle);
        if (!obj)
                return -ENOENT;

        /* Pinned buffers may be scanout, so flush the cache */
        i915_gem_object_flush_if_display(obj);
        i915_gem_object_put(obj);

        return 0;
}

/**
 * i915_gem_mmap_ioctl - Maps the contents of an object, returning the address
 *                       it is mapped to.
 * @dev: drm device
 * @data: ioctl data blob
 * @file: drm file
 *
 * While the mapping holds a reference on the contents of the object, it doesn't
 * imply a ref on the object itself.
 *
 * IMPORTANT:
 *
 * DRM driver writers who look a this function as an example for how to do GEM
 * mmap support, please don't implement mmap support like here. The modern way
 * to implement DRM mmap support is with an mmap offset ioctl (like
 * i915_gem_mmap_gtt) and then using the mmap syscall on the DRM fd directly.
 * That way debug tooling like valgrind will understand what's going on, hiding
 * the mmap call in a driver private ioctl will break that. The i915 driver only
 * does cpu mmaps this way because we didn't know better.
 */
int
i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
                    struct drm_file *file)
{
        struct drm_i915_gem_mmap *args = data;
        struct drm_i915_gem_object *obj;
        unsigned long addr;

        if (args->flags & ~(I915_MMAP_WC))
                return -EINVAL;

        if (args->flags & I915_MMAP_WC && !boot_cpu_has(X86_FEATURE_PAT))
                return -ENODEV;

        obj = i915_gem_object_lookup(file, args->handle);
        if (!obj)
                return -ENOENT;

        /* prime objects have no backing filp to GEM mmap
         * pages from.
         */
        if (!obj->base.filp) {
                i915_gem_object_put(obj);
                return -EINVAL;
        }

        addr = vm_mmap(obj->base.filp, 0, args->size,
                       PROT_READ | PROT_WRITE, MAP_SHARED,
                       args->offset);
        if (args->flags & I915_MMAP_WC) {
                struct mm_struct *mm = current->mm;
                struct vm_area_struct *vma;

                if (down_write_killable(&mm->mmap_sem)) {
                        i915_gem_object_put(obj);
                        return -EINTR;
                }
                vma = find_vma(mm, addr);
                if (vma)
                        vma->vm_page_prot =
                                pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
                else
                        addr = -ENOMEM;
                up_write(&mm->mmap_sem);

                /* This may race, but that's ok, it only gets set */
                WRITE_ONCE(obj->frontbuffer_ggtt_origin, ORIGIN_CPU);
        }
        i915_gem_object_put(obj);
        if (IS_ERR((void *)addr))
                return addr;

        args->addr_ptr = (uint64_t) addr;

        return 0;
}

static unsigned int tile_row_pages(struct drm_i915_gem_object *obj)
{
        return i915_gem_object_get_tile_row_size(obj) >> PAGE_SHIFT;
}

/**
 * i915_gem_mmap_gtt_version - report the current feature set for GTT mmaps
 *
 * A history of the GTT mmap interface:
 *
 * 0 - Everything had to fit into the GTT. Both parties of a memcpy had to
 *     aligned and suitable for fencing, and still fit into the available
 *     mappable space left by the pinned display objects. A classic problem
 *     we called the page-fault-of-doom where we would ping-pong between
 *     two objects that could not fit inside the GTT and so the memcpy
 *     would page one object in at the expense of the other between every
 *     single byte.
 *
 * 1 - Objects can be any size, and have any compatible fencing (X Y, or none
 *     as set via i915_gem_set_tiling() [DRM_I915_GEM_SET_TILING]). If the
 *     object is too large for the available space (or simply too large
 *     for the mappable aperture!), a view is created instead and faulted
 *     into userspace. (This view is aligned and sized appropriately for
 *     fenced access.)
 *
 * 2 - Recognise WC as a separate cache domain so that we can flush the
 *     delayed writes via GTT before performing direct access via WC.
 *
 * Restrictions:
 *
 *  * snoopable objects cannot be accessed via the GTT. It can cause machine
 *    hangs on some architectures, corruption on others. An attempt to service
 *    a GTT page fault from a snoopable object will generate a SIGBUS.
 *
 *  * the object must be able to fit into RAM (physical memory, though no
 *    limited to the mappable aperture).
 *
 *
 * Caveats:
 *
 *  * a new GTT page fault will synchronize rendering from the GPU and flush
 *    all data to system memory. Subsequent access will not be synchronized.
 *
 *  * all mappings are revoked on runtime device suspend.
 *
 *  * there are only 8, 16 or 32 fence registers to share between all users
 *    (older machines require fence register for display and blitter access
 *    as well). Contention of the fence registers will cause the previous users
 *    to be unmapped and any new access will generate new page faults.
 *
 *  * running out of memory while servicing a fault may generate a SIGBUS,
 *    rather than the expected SIGSEGV.
 */
int i915_gem_mmap_gtt_version(void)
{
        return 2;
}

static inline struct i915_ggtt_view
compute_partial_view(struct drm_i915_gem_object *obj,
                     pgoff_t page_offset,
                     unsigned int chunk)
{
        struct i915_ggtt_view view;

        if (i915_gem_object_is_tiled(obj))
                chunk = roundup(chunk, tile_row_pages(obj));

        view.type = I915_GGTT_VIEW_PARTIAL;
        view.partial.offset = rounddown(page_offset, chunk);
        view.partial.size =
                min_t(unsigned int, chunk,
                      (obj->base.size >> PAGE_SHIFT) - view.partial.offset);

        /* If the partial covers the entire object, just create a normal VMA. */
        if (chunk >= obj->base.size >> PAGE_SHIFT)
                view.type = I915_GGTT_VIEW_NORMAL;

        return view;
}

/**
 * i915_gem_fault - fault a page into the GTT
 * @vmf: fault info
 *
 * The fault handler is set up by drm_gem_mmap() when a object is GTT mapped
 * from userspace.  The fault handler takes care of binding the object to
 * the GTT (if needed), allocating and programming a fence register (again,
 * only if needed based on whether the old reg is still valid or the object
 * is tiled) and inserting a new PTE into the faulting process.
 *
 * Note that the faulting process may involve evicting existing objects
 * from the GTT and/or fence registers to make room.  So performance may
 * suffer if the GTT working set is large or there are few fence registers
 * left.
 *
 * The current feature set supported by i915_gem_fault() and thus GTT mmaps
 * is exposed via I915_PARAM_MMAP_GTT_VERSION (see i915_gem_mmap_gtt_version).
 */
int i915_gem_fault(struct vm_fault *vmf)
{
#define MIN_CHUNK_PAGES ((1 << 20) >> PAGE_SHIFT) /* 1 MiB */
        struct vm_area_struct *area = vmf->vma;
        struct drm_i915_gem_object *obj = to_intel_bo(area->vm_private_data);
        struct drm_device *dev = obj->base.dev;
        struct drm_i915_private *dev_priv = to_i915(dev);
        struct i915_ggtt *ggtt = &dev_priv->ggtt;
        bool write = !!(vmf->flags & FAULT_FLAG_WRITE);
        struct i915_vma *vma;
        pgoff_t page_offset;
        unsigned int flags;
        int ret;

        /* We don't use vmf->pgoff since that has the fake offset */
        page_offset = (vmf->address - area->vm_start) >> PAGE_SHIFT;

        trace_i915_gem_object_fault(obj, page_offset, true, write);

        /* Try to flush the object off the GPU first without holding the lock.
         * Upon acquiring the lock, we will perform our sanity checks and then
         * repeat the flush holding the lock in the normal manner to catch cases
         * where we are gazumped.
         */
        ret = i915_gem_object_wait(obj,
                                   I915_WAIT_INTERRUPTIBLE,
                                   MAX_SCHEDULE_TIMEOUT,
                                   NULL);
        if (ret)
                goto err;

        ret = i915_gem_object_pin_pages(obj);
        if (ret)
                goto err;

        intel_runtime_pm_get(dev_priv);

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

        /* Access to snoopable pages through the GTT is incoherent. */
        if (obj->cache_level != I915_CACHE_NONE && !HAS_LLC(dev_priv)) {
                ret = -EFAULT;
                goto err_unlock;
        }

        /* If the object is smaller than a couple of partial vma, it is
         * not worth only creating a single partial vma - we may as well
         * clear enough space for the full object.
         */
        flags = PIN_MAPPABLE;
        if (obj->base.size > 2 * MIN_CHUNK_PAGES << PAGE_SHIFT)
                flags |= PIN_NONBLOCK | PIN_NONFAULT;

        /* Now pin it into the GTT as needed */
        vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0, flags);
        if (IS_ERR(vma)) {
                /* Use a partial view if it is bigger than available space */
                struct i915_ggtt_view view =
                        compute_partial_view(obj, page_offset, MIN_CHUNK_PAGES);

                /* Userspace is now writing through an untracked VMA, abandon
                 * all hope that the hardware is able to track future writes.
                 */
                obj->frontbuffer_ggtt_origin = ORIGIN_CPU;

                vma = i915_gem_object_ggtt_pin(obj, &view, 0, 0, PIN_MAPPABLE);
        }
        if (IS_ERR(vma)) {
                ret = PTR_ERR(vma);
                goto err_unlock;
        }

        ret = i915_gem_object_set_to_gtt_domain(obj, write);
        if (ret)
                goto err_unpin;

        ret = i915_vma_pin_fence(vma);
        if (ret)
                goto err_unpin;

        /* Finally, remap it using the new GTT offset */
        ret = remap_io_mapping(area,
                               area->vm_start + (vma->ggtt_view.partial.offset << PAGE_SHIFT),
                               (ggtt->mappable_base + vma->node.start) >> PAGE_SHIFT,
                               min_t(u64, vma->size, area->vm_end - area->vm_start),
                               &ggtt->mappable);
        if (ret)
                goto err_fence;

        /* Mark as being mmapped into userspace for later revocation */
        assert_rpm_wakelock_held(dev_priv);
        if (!i915_vma_set_userfault(vma) && !obj->userfault_count++)
                list_add(&obj->userfault_link, &dev_priv->mm.userfault_list);
        GEM_BUG_ON(!obj->userfault_count);

err_fence:
        i915_vma_unpin_fence(vma);
err_unpin:
        __i915_vma_unpin(vma);
err_unlock:
        mutex_unlock(&dev->struct_mutex);
err_rpm:
        intel_runtime_pm_put(dev_priv);
        i915_gem_object_unpin_pages(obj);
err:
        switch (ret) {
        case -EIO:
                /*
                 * We eat errors when the gpu is terminally wedged to avoid
                 * userspace unduly crashing (gl has no provisions for mmaps to
                 * fail). But any other -EIO isn't ours (e.g. swap in failure)
                 * and so needs to be reported.
                 */
                if (!i915_terminally_wedged(&dev_priv->gpu_error)) {
                        ret = VM_FAULT_SIGBUS;
                        break;
                }
        case -EAGAIN:
                /*
                 * EAGAIN means the gpu is hung and we'll wait for the error
                 * handler to reset everything when re-faulting in
                 * i915_mutex_lock_interruptible.
                 */
        case 0:
        case -ERESTARTSYS:
        case -EINTR:
        case -EBUSY:
                /*
                 * EBUSY is ok: this just means that another thread
                 * already did the job.
                 */
                ret = VM_FAULT_NOPAGE;
                break;
        case -ENOMEM:
                ret = VM_FAULT_OOM;
                break;
        case -ENOSPC:
        case -EFAULT:
                ret = VM_FAULT_SIGBUS;
                break;
        default:
                WARN_ONCE(ret, "unhandled error in i915_gem_fault: %i\n", ret);
                ret = VM_FAULT_SIGBUS;
                break;
        }
        return ret;
}

static void __i915_gem_object_release_mmap(struct drm_i915_gem_object *obj)
{
        struct i915_vma *vma;

        GEM_BUG_ON(!obj->userfault_count);

        obj->userfault_count = 0;
        list_del(&obj->userfault_link);
        drm_vma_node_unmap(&obj->base.vma_node,
                           obj->base.dev->anon_inode->i_mapping);

        list_for_each_entry(vma, &obj->vma_list, obj_link) {
                if (!i915_vma_is_ggtt(vma))
                        break;

                i915_vma_unset_userfault(vma);
        }
}

/**
 * i915_gem_release_mmap - remove physical page mappings
 * @obj: obj in question
 *
 * Preserve the reservation of the mmapping with the DRM core code, but
 * relinquish ownership of the pages back to the system.
 *
 * It is vital that we remove the page mapping if we have mapped a tiled
 * object through the GTT and then lose the fence register due to
 * resource pressure. Similarly if the object has been moved out of the
 * aperture, than pages mapped into userspace must be revoked. Removing the
 * mapping will then trigger a page fault on the next user access, allowing
 * fixup by i915_gem_fault().
 */
void
i915_gem_release_mmap(struct drm_i915_gem_object *obj)
{
        struct drm_i915_private *i915 = to_i915(obj->base.dev);

        /* Serialisation between user GTT access and our code depends upon
         * revoking the CPU's PTE whilst the mutex is held. The next user
         * pagefault then has to wait until we release the mutex.
         *
         * Note that RPM complicates somewhat by adding an additional
         * requirement that operations to the GGTT be made holding the RPM
         * wakeref.
         */
        lockdep_assert_held(&i915->drm.struct_mutex);
        intel_runtime_pm_get(i915);

        if (!obj->userfault_count)
                goto out;

        __i915_gem_object_release_mmap(obj);

        /* Ensure that the CPU's PTE are revoked and there are not outstanding
         * memory transactions from userspace before we return. The TLB
         * flushing implied above by changing the PTE above *should* be
         * sufficient, an extra barrier here just provides us with a bit
         * of paranoid documentation about our requirement to serialise
         * memory writes before touching registers / GSM.
         */
        wmb();

out:
        intel_runtime_pm_put(i915);
}

void i915_gem_runtime_suspend(struct drm_i915_private *dev_priv)
{
        struct drm_i915_gem_object *obj, *on;
        int i;

        /*
         * Only called during RPM suspend. All users of the userfault_list
         * must be holding an RPM wakeref to ensure that this can not
         * run concurrently with themselves (and use the struct_mutex for
         * protection between themselves).
         */

        list_for_each_entry_safe(obj, on,
                                 &dev_priv->mm.userfault_list, userfault_link)
                __i915_gem_object_release_mmap(obj);

        /* The fence will be lost when the device powers down. If any were
         * in use by hardware (i.e. they are pinned), we should not be powering
         * down! All other fences will be reacquired by the user upon waking.
         */
        for (i = 0; i < dev_priv->num_fence_regs; i++) {
                struct drm_i915_fence_reg *reg = &dev_priv->fence_regs[i];

                /* Ideally we want to assert that the fence register is not
                 * live at this point (i.e. that no piece of code will be
                 * trying to write through fence + GTT, as that both violates
                 * our tracking of activity and associated locking/barriers,
                 * but also is illegal given that the hw is powered down).
                 *
                 * Previously we used reg->pin_count as a "liveness" indicator.
                 * That is not sufficient, and we need a more fine-grained
                 * tool if we want to have a sanity check here.
                 */

                if (!reg->vma)
                        continue;

                GEM_BUG_ON(i915_vma_has_userfault(reg->vma));
                reg->dirty = true;
        }
}

static int i915_gem_object_create_mmap_offset(struct drm_i915_gem_object *obj)
{
        struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
        int err;

        err = drm_gem_create_mmap_offset(&obj->base);
        if (likely(!err))
                return 0;

        /* Attempt to reap some mmap space from dead objects */
        do {
                err = i915_gem_wait_for_idle(dev_priv, I915_WAIT_INTERRUPTIBLE);
                if (err)
                        break;

                i915_gem_drain_freed_objects(dev_priv);
                err = drm_gem_create_mmap_offset(&obj->base);
                if (!err)
                        break;

        } while (flush_delayed_work(&dev_priv->gt.retire_work));

        return err;
}

static void i915_gem_object_free_mmap_offset(struct drm_i915_gem_object *obj)
{
        drm_gem_free_mmap_offset(&obj->base);
}

int
i915_gem_mmap_gtt(struct drm_file *file,
                  struct drm_device *dev,
                  uint32_t handle,
                  uint64_t *offset)
{
        struct drm_i915_gem_object *obj;
        int ret;

        obj = i915_gem_object_lookup(file, handle);
        if (!obj)
                return -ENOENT;

        ret = i915_gem_object_create_mmap_offset(obj);
        if (ret == 0)
                *offset = drm_vma_node_offset_addr(&obj->base.vma_node);

        i915_gem_object_put(obj);
        return ret;
}

/**
 * i915_gem_mmap_gtt_ioctl - prepare an object for GTT mmap'ing
 * @dev: DRM device
 * @data: GTT mapping ioctl data
 * @file: GEM object info
 *
 * Simply returns the fake offset to userspace so it can mmap it.
 * The mmap call will end up in drm_gem_mmap(), which will set things
 * up so we can get faults in the handler above.
 *
 * The fault handler will take care of binding the object into the GTT
 * (since it may have been evicted to make room for something), allocating
 * a fence register, and mapping the appropriate aperture address into
 * userspace.
 */
int
i915_gem_mmap_gtt_ioctl(struct drm_device *dev, void *data,
                        struct drm_file *file)
{
        struct drm_i915_gem_mmap_gtt *args = data;

        return i915_gem_mmap_gtt(file, dev, args->handle, &args->offset);
}

/* Immediately discard the backing storage */
static void
i915_gem_object_truncate(struct drm_i915_gem_object *obj)
{
        i915_gem_object_free_mmap_offset(obj);

        if (obj->base.filp == NULL)
                return;

        /* Our goal here is to return as much of the memory as
         * is possible back to the system as we are called from OOM.
         * To do this we must instruct the shmfs to drop all of its
         * backing pages, *now*.
         */
        shmem_truncate_range(file_inode(obj->base.filp), 0, (loff_t)-1);
        obj->mm.madv = __I915_MADV_PURGED;
        obj->mm.pages = ERR_PTR(-EFAULT);
}

/* Try to discard unwanted pages */
void __i915_gem_object_invalidate(struct drm_i915_gem_object *obj)
{
        struct address_space *mapping;

        lockdep_assert_held(&obj->mm.lock);
        GEM_BUG_ON(i915_gem_object_has_pages(obj));

        switch (obj->mm.madv) {
        case I915_MADV_DONTNEED:
                i915_gem_object_truncate(obj);
        case __I915_MADV_PURGED:
                return;
        }

        if (obj->base.filp == NULL)
                return;

        mapping = obj->base.filp->f_mapping,
        invalidate_mapping_pages(mapping, 0, (loff_t)-1);
}

static void
i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
                              struct sg_table *pages)
{
        struct sgt_iter sgt_iter;
        struct page *page;

        __i915_gem_object_release_shmem(obj, pages, true);

        i915_gem_gtt_finish_pages(obj, pages);

        if (i915_gem_object_needs_bit17_swizzle(obj))
                i915_gem_object_save_bit_17_swizzle(obj, pages);

        for_each_sgt_page(page, sgt_iter, pages) {
                if (obj->mm.dirty)
                        set_page_dirty(page);

                if (obj->mm.madv == I915_MADV_WILLNEED)
                        mark_page_accessed(page);

                put_page(page);
        }
        obj->mm.dirty = false;

        sg_free_table(pages);
        kfree(pages);
}

static void __i915_gem_object_reset_page_iter(struct drm_i915_gem_object *obj)
{
        struct radix_tree_iter iter;
        void __rcu **slot;

        rcu_read_lock();
        radix_tree_for_each_slot(slot, &obj->mm.get_page.radix, &iter, 0)
                radix_tree_delete(&obj->mm.get_page.radix, iter.index);
        rcu_read_unlock();
}

void __i915_gem_object_put_pages(struct drm_i915_gem_object *obj,
                                 enum i915_mm_subclass subclass)
{
        struct drm_i915_private *i915 = to_i915(obj->base.dev);
        struct sg_table *pages;

        if (i915_gem_object_has_pinned_pages(obj))
                return;

        GEM_BUG_ON(obj->bind_count);
        if (!i915_gem_object_has_pages(obj))
                return;

        /* May be called by shrinker from within get_pages() (on another bo) */
        mutex_lock_nested(&obj->mm.lock, subclass);
        if (unlikely(atomic_read(&obj->mm.pages_pin_count)))
                goto unlock;

        /* ->put_pages might need to allocate memory for the bit17 swizzle
         * array, hence protect them from being reaped by removing them from gtt
         * lists early. */
        pages = fetch_and_zero(&obj->mm.pages);
        GEM_BUG_ON(!pages);

        spin_lock(&i915->mm.obj_lock);
        list_del(&obj->mm.link);
        spin_unlock(&i915->mm.obj_lock);

        if (obj->mm.mapping) {
                void *ptr;

                ptr = page_mask_bits(obj->mm.mapping);
                if (is_vmalloc_addr(ptr))
                        vunmap(ptr);
                else
                        kunmap(kmap_to_page(ptr));

                obj->mm.mapping = NULL;
        }

        __i915_gem_object_reset_page_iter(obj);

        if (!IS_ERR(pages))
                obj->ops->put_pages(obj, pages);

        obj->mm.page_sizes.phys = obj->mm.page_sizes.sg = 0;

unlock:
        mutex_unlock(&obj->mm.lock);
}

static bool i915_sg_trim(struct sg_table *orig_st)
{
        struct sg_table new_st;
        struct scatterlist *sg, *new_sg;
        unsigned int i;

        if (orig_st->nents == orig_st->orig_nents)
                return false;

        if (sg_alloc_table(&new_st, orig_st->nents, GFP_KERNEL | __GFP_NOWARN))
                return false;

        new_sg = new_st.sgl;
        for_each_sg(orig_st->sgl, sg, orig_st->nents, i) {
                sg_set_page(new_sg, sg_page(sg), sg->length, 0);
                /* called before being DMA mapped, no need to copy sg->dma_* */
                new_sg = sg_next(new_sg);
        }
        GEM_BUG_ON(new_sg); /* Should walk exactly nents and hit the end */

        sg_free_table(orig_st);

        *orig_st = new_st;
        return true;
}

static int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
{
        struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
        const unsigned long page_count = obj->base.size / PAGE_SIZE;
        unsigned long i;
        struct address_space *mapping;
        struct sg_table *st;
        struct scatterlist *sg;
        struct sgt_iter sgt_iter;
        struct page *page;
        unsigned long last_pfn = 0;     /* suppress gcc warning */
        unsigned int max_segment = i915_sg_segment_size();
        unsigned int sg_page_sizes;
        gfp_t noreclaim;
        int ret;

        /* Assert that the object is not currently in any GPU domain. As it
         * wasn't in the GTT, there shouldn't be any way it could have been in
         * a GPU cache
         */
        GEM_BUG_ON(obj->base.read_domains & I915_GEM_GPU_DOMAINS);
        GEM_BUG_ON(obj->base.write_domain & I915_GEM_GPU_DOMAINS);

        st = kmalloc(sizeof(*st), GFP_KERNEL);
        if (st == NULL)
                return -ENOMEM;

rebuild_st:
        if (sg_alloc_table(st, page_count, GFP_KERNEL)) {
                kfree(st);
                return -ENOMEM;
        }

        /* Get the list of pages out of our struct file.  They'll be pinned
         * at this point until we release them.
         *
         * Fail silently without starting the shrinker
         */
        mapping = obj->base.filp->f_mapping;
        noreclaim = mapping_gfp_constraint(mapping, ~__GFP_RECLAIM);
        noreclaim |= __GFP_NORETRY | __GFP_NOWARN;

        sg = st->sgl;
        st->nents = 0;
        sg_page_sizes = 0;
        for (i = 0; i < page_count; i++) {
                const unsigned int shrink[] = {
                        I915_SHRINK_BOUND | I915_SHRINK_UNBOUND | I915_SHRINK_PURGEABLE,
                        0,
                }, *s = shrink;
                gfp_t gfp = noreclaim;

                do {
                        page = shmem_read_mapping_page_gfp(mapping, i, gfp);
                        if (likely(!IS_ERR(page)))
                                break;

                        if (!*s) {
                                ret = PTR_ERR(page);
                                goto err_sg;
                        }

                        i915_gem_shrink(dev_priv, 2 * page_count, NULL, *s++);
                        cond_resched();

                        /* We've tried hard to allocate the memory by reaping
                         * our own buffer, now let the real VM do its job and
                         * go down in flames if truly OOM.
                         *
                         * However, since graphics tend to be disposable,
                         * defer the oom here by reporting the ENOMEM back
                         * to userspace.
                         */
                        if (!*s) {
                                /* reclaim and warn, but no oom */
                                gfp = mapping_gfp_mask(mapping);

                                /* Our bo are always dirty and so we require
                                 * kswapd to reclaim our pages (direct reclaim
                                 * does not effectively begin pageout of our
                                 * buffers on its own). However, direct reclaim
                                 * only waits for kswapd when under allocation
                                 * congestion. So as a result __GFP_RECLAIM is
                                 * unreliable and fails to actually reclaim our
                                 * dirty pages -- unless you try over and over
                                 * again with !__GFP_NORETRY. However, we still
                                 * want to fail this allocation rather than
                                 * trigger the out-of-memory killer and for
                                 * this we want __GFP_RETRY_MAYFAIL.
                                 */
                                gfp |= __GFP_RETRY_MAYFAIL;
                        }
                } while (1);

                if (!i ||
                    sg->length >= max_segment ||
                    page_to_pfn(page) != last_pfn + 1) {
                        if (i) {
                                sg_page_sizes |= sg->length;
                                sg = sg_next(sg);
                        }
                        st->nents++;
                        sg_set_page(sg, page, PAGE_SIZE, 0);
                } else {
                        sg->length += PAGE_SIZE;
                }
                last_pfn = page_to_pfn(page);

                /* Check that the i965g/gm workaround works. */
                WARN_ON((gfp & __GFP_DMA32) && (last_pfn >= 0x00100000UL));
        }
        if (sg) { /* loop terminated early; short sg table */
                sg_page_sizes |= sg->length;
                sg_mark_end(sg);
        }

        /* Trim unused sg entries to avoid wasting memory. */
        i915_sg_trim(st);

        ret = i915_gem_gtt_prepare_pages(obj, st);
        if (ret) {
                /* DMA remapping failed? One possible cause is that
                 * it could not reserve enough large entries, asking
                 * for PAGE_SIZE chunks instead may be helpful.
                 */
                if (max_segment > PAGE_SIZE) {
                        for_each_sgt_page(page, sgt_iter, st)
                                put_page(page);
                        sg_free_table(st);

                        max_segment = PAGE_SIZE;
                        goto rebuild_st;
                } else {
                        dev_warn(&dev_priv->drm.pdev->dev,
                                 "Failed to DMA remap %lu pages\n",
                                 page_count);
                        goto err_pages;
                }
        }

        if (i915_gem_object_needs_bit17_swizzle(obj))
                i915_gem_object_do_bit_17_swizzle(obj, st);

        __i915_gem_object_set_pages(obj, st, sg_page_sizes);

        return 0;

err_sg:
        sg_mark_end(sg);
err_pages:
        for_each_sgt_page(page, sgt_iter, st)
                put_page(page);
        sg_free_table(st);
        kfree(st);

        /* shmemfs first checks if there is enough memory to allocate the page
         * and reports ENOSPC should there be insufficient, along with the usual
         * ENOMEM for a genuine allocation failure.
         *
         * We use ENOSPC in our driver to mean that we have run out of aperture
         * space and so want to translate the error from shmemfs back to our
         * usual understanding of ENOMEM.
         */
        if (ret == -ENOSPC)
                ret = -ENOMEM;

        return ret;
}

void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
                                 struct sg_table *pages,
                                 unsigned int sg_page_sizes)
{
        struct drm_i915_private *i915 = to_i915(obj->base.dev);
        unsigned long supported = INTEL_INFO(i915)->page_sizes;
        int i;

        lockdep_assert_held(&obj->mm.lock);

        obj->mm.get_page.sg_pos = pages->sgl;
        obj->mm.get_page.sg_idx = 0;

        obj->mm.pages = pages;

        if (i915_gem_object_is_tiled(obj) &&
            i915->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
                GEM_BUG_ON(obj->mm.quirked);
                __i915_gem_object_pin_pages(obj);
                obj->mm.quirked = true;
        }

        GEM_BUG_ON(!sg_page_sizes);
        obj->mm.page_sizes.phys = sg_page_sizes;

        /*
         * Calculate the supported page-sizes which fit into the given
         * sg_page_sizes. This will give us the page-sizes which we may be able
         * to use opportunistically when later inserting into the GTT. For
         * example if phys=2G, then in theory we should be able to use 1G, 2M,
         * 64K or 4K pages, although in practice this will depend on a number of
         * other factors.
         */
        obj->mm.page_sizes.sg = 0;
        for_each_set_bit(i, &supported, ilog2(I915_GTT_MAX_PAGE_SIZE) + 1) {
                if (obj->mm.page_sizes.phys & ~0u << i)
                        obj->mm.page_sizes.sg |= BIT(i);
        }
        GEM_BUG_ON(!HAS_PAGE_SIZES(i915, obj->mm.page_sizes.sg));

        spin_lock(&i915->mm.obj_lock);
        list_add(&obj->mm.link, &i915->mm.unbound_list);
        spin_unlock(&i915->mm.obj_lock);
}

static int ____i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
{
        int err;

        if (unlikely(obj->mm.madv != I915_MADV_WILLNEED)) {
                DRM_DEBUG("Attempting to obtain a purgeable object\n");
                return -EFAULT;
        }

        err = obj->ops->get_pages(obj);
        GEM_BUG_ON(!err && IS_ERR_OR_NULL(obj->mm.pages));

        return err;
}

/* Ensure that the associated pages are gathered from the backing storage
 * and pinned into our object. i915_gem_object_pin_pages() may be called
 * multiple times before they are released by a single call to
 * i915_gem_object_unpin_pages() - once the pages are no longer referenced
 * either as a result of memory pressure (reaping pages under the shrinker)
 * or as the object is itself released.
 */
int __i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
{
        int err;

        err = mutex_lock_interruptible(&obj->mm.lock);
        if (err)
                return err;

        if (unlikely(!i915_gem_object_has_pages(obj))) {
                GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));

                err = ____i915_gem_object_get_pages(obj);
                if (err)
                        goto unlock;

                smp_mb__before_atomic();
        }
        atomic_inc(&obj->mm.pages_pin_count);

unlock:
        mutex_unlock(&obj->mm.lock);
        return err;
}

/* The 'mapping' part of i915_gem_object_pin_map() below */
static void *i915_gem_object_map(const struct drm_i915_gem_object *obj,
                                 enum i915_map_type type)
{
        unsigned long n_pages = obj->base.size >> PAGE_SHIFT;
        struct sg_table *sgt = obj->mm.pages;
        struct sgt_iter sgt_iter;
        struct page *page;
        struct page *stack_pages[32];
        struct page **pages = stack_pages;
        unsigned long i = 0;
        pgprot_t pgprot;
        void *addr;

        /* A single page can always be kmapped */
        if (n_pages == 1 && type == I915_MAP_WB)
                return kmap(sg_page(sgt->sgl));

        if (n_pages > ARRAY_SIZE(stack_pages)) {
                /* Too big for stack -- allocate temporary array instead */
                pages = kvmalloc_array(n_pages, sizeof(*pages), GFP_KERNEL);
                if (!pages)
                        return NULL;
        }

        for_each_sgt_page(page, sgt_iter, sgt)
                pages[i++] = page;

        /* Check that we have the expected number of pages */
        GEM_BUG_ON(i != n_pages);

        switch (type) {
        default:
                MISSING_CASE(type);
                /* fallthrough to use PAGE_KERNEL anyway */
        case I915_MAP_WB:
                pgprot = PAGE_KERNEL;
                break;
        case I915_MAP_WC:
                pgprot = pgprot_writecombine(PAGE_KERNEL_IO);
                break;
        }
        addr = vmap(pages, n_pages, 0, pgprot);

        if (pages != stack_pages)
                kvfree(pages);

        return addr;
}

/* get, pin, and map the pages of the object into kernel space */
void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
                              enum i915_map_type type)
{
        enum i915_map_type has_type;
        bool pinned;
        void *ptr;
        int ret;

        GEM_BUG_ON(!i915_gem_object_has_struct_page(obj));

        ret = mutex_lock_interruptible(&obj->mm.lock);
        if (ret)
                return ERR_PTR(ret);

        pinned = !(type & I915_MAP_OVERRIDE);
        type &= ~I915_MAP_OVERRIDE;

        if (!atomic_inc_not_zero(&obj->mm.pages_pin_count)) {
                if (unlikely(!i915_gem_object_has_pages(obj))) {
                        GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));

                        ret = ____i915_gem_object_get_pages(obj);
                        if (ret)
                                goto err_unlock;

                        smp_mb__before_atomic();
                }
                atomic_inc(&obj->mm.pages_pin_count);
                pinned = false;
        }
        GEM_BUG_ON(!i915_gem_object_has_pages(obj));

        ptr = page_unpack_bits(obj->mm.mapping, &has_type);
        if (ptr && has_type != type) {
                if (pinned) {
                        ret = -EBUSY;
                        goto err_unpin;
                }

                if (is_vmalloc_addr(ptr))
                        vunmap(ptr);
                else
                        kunmap(kmap_to_page(ptr));

                ptr = obj->mm.mapping = NULL;
        }

        if (!ptr) {
                ptr = i915_gem_object_map(obj, type);
                if (!ptr) {
                        ret = -ENOMEM;
                        goto err_unpin;
                }

                obj->mm.mapping = page_pack_bits(ptr, type);
        }

out_unlock:
        mutex_unlock(&obj->mm.lock);
        return ptr;

err_unpin:
        atomic_dec(&obj->mm.pages_pin_count);
err_unlock:
        ptr = ERR_PTR(ret);
        goto out_unlock;
}

static int
i915_gem_object_pwrite_gtt(struct drm_i915_gem_object *obj,
                           const struct drm_i915_gem_pwrite *arg)
{
        struct address_space *mapping = obj->base.filp->f_mapping;
        char __user *user_data = u64_to_user_ptr(arg->data_ptr);
        u64 remain, offset;
        unsigned int pg;

        /* Before we instantiate/pin the backing store for our use, we
         * can prepopulate the shmemfs filp efficiently using a write into
         * the pagecache. We avoid the penalty of instantiating all the
         * pages, important if the user is just writing to a few and never
         * uses the object on the GPU, and using a direct write into shmemfs
         * allows it to avoid the cost of retrieving a page (either swapin
         * or clearing-before-use) before it is overwritten.
         */
        if (i915_gem_object_has_pages(obj))
                return -ENODEV;

        if (obj->mm.madv != I915_MADV_WILLNEED)
                return -EFAULT;

        /* Before the pages are instantiated the object is treated as being
         * in the CPU domain. The pages will be clflushed as required before
         * use, and we can freely write into the pages directly. If userspace
         * races pwrite with any other operation; corruption will ensue -
         * that is userspace's prerogative!
         */

        remain = arg->size;
        offset = arg->offset;
        pg = offset_in_page(offset);

        do {
                unsigned int len, unwritten;
                struct page *page;
                void *data, *vaddr;
                int err;

                len = PAGE_SIZE - pg;
                if (len > remain)
                        len = remain;

                err = pagecache_write_begin(obj->base.filp, mapping,
                                            offset, len, 0,
                                            &page, &data);
                if (err < 0)
                        return err;

                vaddr = kmap(page);
                unwritten = copy_from_user(vaddr + pg, user_data, len);
                kunmap(page);

                err = pagecache_write_end(obj->base.filp, mapping,
                                          offset, len, len - unwritten,
                                          page, data);
                if (err < 0)
                        return err;

                if (unwritten)
                        return -EFAULT;

                remain -= len;
                user_data += len;
                offset += len;
                pg = 0;
        } while (remain);

        return 0;
}

static bool ban_context(const struct i915_gem_context *ctx,
                        unsigned int score)
{
        return (i915_gem_context_is_bannable(ctx) &&
                score >= CONTEXT_SCORE_BAN_THRESHOLD);
}

static void i915_gem_context_mark_guilty(struct i915_gem_context *ctx)
{
        unsigned int score;
        bool banned;

        atomic_inc(&ctx->guilty_count);

        score = atomic_add_return(CONTEXT_SCORE_GUILTY, &ctx->ban_score);
        banned = ban_context(ctx, score);
        DRM_DEBUG_DRIVER("context %s marked guilty (score %d) banned? %s\n",
                         ctx->name, score, yesno(banned));
        if (!banned)
                return;

        i915_gem_context_set_banned(ctx);
        if (!IS_ERR_OR_NULL(ctx->file_priv)) {
                atomic_inc(&ctx->file_priv->context_bans);
                DRM_DEBUG_DRIVER("client %s has had %d context banned\n",
                                 ctx->name, atomic_read(&ctx->file_priv->context_bans));
        }
}

static void i915_gem_context_mark_innocent(struct i915_gem_context *ctx)
{
        atomic_inc(&ctx->active_count);
}

struct drm_i915_gem_request *
i915_gem_find_active_request(struct intel_engine_cs *engine)
{
        struct drm_i915_gem_request *request, *active = NULL;
        unsigned long flags;

        /* We are called by the error capture and reset at a random
         * point in time. In particular, note that neither is crucially
         * ordered with an interrupt. After a hang, the GPU is dead and we
         * assume that no more writes can happen (we waited long enough for
         * all writes that were in transaction to be flushed) - adding an
         * extra delay for a recent interrupt is pointless. Hence, we do
         * not need an engine->irq_seqno_barrier() before the seqno reads.
         */
        spin_lock_irqsave(&engine->timeline->lock, flags);
        list_for_each_entry(request, &engine->timeline->requests, link) {
                if (__i915_gem_request_completed(request,
                                                 request->global_seqno))
                        continue;

                GEM_BUG_ON(request->engine != engine);
                GEM_BUG_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
                                    &request->fence.flags));

                active = request;
                break;
        }
        spin_unlock_irqrestore(&engine->timeline->lock, flags);

        return active;
}

static bool engine_stalled(struct intel_engine_cs *engine)
{
        if (!engine->hangcheck.stalled)
                return false;

        /* Check for possible seqno movement after hang declaration */
        if (engine->hangcheck.seqno != intel_engine_get_seqno(engine)) {
                DRM_DEBUG_DRIVER("%s pardoned\n", engine->name);
                return false;
        }

        return true;
}

/*
 * Ensure irq handler finishes, and not run again.
 * Also return the active request so that we only search for it once.
 */
struct drm_i915_gem_request *
i915_gem_reset_prepare_engine(struct intel_engine_cs *engine)
{
        struct drm_i915_gem_request *request = NULL;

        /*
         * During the reset sequence, we must prevent the engine from
         * entering RC6. As the context state is undefined until we restart
         * the engine, if it does enter RC6 during the reset, the state
         * written to the powercontext is undefined and so we may lose
         * GPU state upon resume, i.e. fail to restart after a reset.
         */
        intel_uncore_forcewake_get(engine->i915, FORCEWAKE_ALL);

        /*
         * Prevent the signaler thread from updating the request
         * state (by calling dma_fence_signal) as we are processing
         * the reset. The write from the GPU of the seqno is
         * asynchronous and the signaler thread may see a different
         * value to us and declare the request complete, even though
         * the reset routine have picked that request as the active
         * (incomplete) request. This conflict is not handled
         * gracefully!
         */
        kthread_park(engine->breadcrumbs.signaler);

        /*
         * Prevent request submission to the hardware until we have
         * completed the reset in i915_gem_reset_finish(). If a request
         * is completed by one engine, it may then queue a request
         * to a second via its engine->irq_tasklet *just* as we are
         * calling engine->init_hw() and also writing the ELSP.
         * Turning off the engine->irq_tasklet until the reset is over
         * prevents the race.
         */
        tasklet_kill(&engine->execlists.irq_tasklet);
        tasklet_disable(&engine->execlists.irq_tasklet);

        if (engine->irq_seqno_barrier)
                engine->irq_seqno_barrier(engine);

        request = i915_gem_find_active_request(engine);
        if (request && request->fence.error == -EIO)
                request = ERR_PTR(-EIO); /* Previous reset failed! */

        return request;
}

int i915_gem_reset_prepare(struct drm_i915_private *dev_priv)
{
        struct intel_engine_cs *engine;
        struct drm_i915_gem_request *request;
        enum intel_engine_id id;
        int err = 0;

        for_each_engine(engine, dev_priv, id) {
                request = i915_gem_reset_prepare_engine(engine);
                if (IS_ERR(request)) {
                        err = PTR_ERR(request);
                        continue;
                }

                engine->hangcheck.active_request = request;
        }

        i915_gem_revoke_fences(dev_priv);

        return err;
}

static void skip_request(struct drm_i915_gem_request *request)
{
        void *vaddr = request->ring->vaddr;
        u32 head;

        /* As this request likely depends on state from the lost
         * context, clear out all the user operations leaving the
         * breadcrumb at the end (so we get the fence notifications).
         */
        head = request->head;
        if (request->postfix < head) {
                memset(vaddr + head, 0, request->ring->size - head);
                head = 0;
        }
        memset(vaddr + head, 0, request->postfix - head);

        dma_fence_set_error(&request->fence, -EIO);
}

static void engine_skip_context(struct drm_i915_gem_request *request)
{
        struct intel_engine_cs *engine = request->engine;
        struct i915_gem_context *hung_ctx = request->ctx;
        struct intel_timeline *timeline;
        unsigned long flags;

        timeline = i915_gem_context_lookup_timeline(hung_ctx, engine);

        spin_lock_irqsave(&engine->timeline->lock, flags);
        spin_lock(&timeline->lock);

        list_for_each_entry_continue(request, &engine->timeline->requests, link)
                if (request->ctx == hung_ctx)
                        skip_request(request);

        list_for_each_entry(request, &timeline->requests, link)
                skip_request(request);

        spin_unlock(&timeline->lock);
        spin_unlock_irqrestore(&engine->timeline->lock, flags);
}

/* Returns the request if it was guilty of the hang */
static struct drm_i915_gem_request *
i915_gem_reset_request(struct intel_engine_cs *engine,
                       struct drm_i915_gem_request *request)
{
        /* The guilty request will get skipped on a hung engine.
         *
         * Users of client default contexts do not rely on logical
         * state preserved between batches so it is safe to execute
         * queued requests following the hang. Non default contexts
         * rely on preserved state, so skipping a batch loses the
         * evolution of the state and it needs to be considered corrupted.
         * Executing more queued batches on top of corrupted state is
         * risky. But we take the risk by trying to advance through
         * the queued requests in order to make the client behaviour
         * more predictable around resets, by not throwing away random
         * amount of batches it has prepared for execution. Sophisticated
         * clients can use gem_reset_stats_ioctl and dma fence status
         * (exported via sync_file info ioctl on explicit fences) to observe
         * when it loses the context state and should rebuild accordingly.
         *
         * The context ban, and ultimately the client ban, mechanism are safety
         * valves if client submission ends up resulting in nothing more than
         * subsequent hangs.
         */

        if (engine_stalled(engine)) {
                i915_gem_context_mark_guilty(request->ctx);
                skip_request(request);

                /* If this context is now banned, skip all pending requests. */
                if (i915_gem_context_is_banned(request->ctx))
                        engine_skip_context(request);
        } else {
                /*
                 * Since this is not the hung engine, it may have advanced
                 * since the hang declaration. Double check by refinding
                 * the active request at the time of the reset.
                 */
                request = i915_gem_find_active_request(engine);
                if (request) {
                        i915_gem_context_mark_innocent(request->ctx);
                        dma_fence_set_error(&request->fence, -EAGAIN);

                        /* Rewind the engine to replay the incomplete rq */
                        spin_lock_irq(&engine->timeline->lock);
                        request = list_prev_entry(request, link);
                        if (&request->link == &engine->timeline->requests)
                                request = NULL;
                        spin_unlock_irq(&engine->timeline->lock);
                }
        }

        return request;
}

void i915_gem_reset_engine(struct intel_engine_cs *engine,
                           struct drm_i915_gem_request *request)
{
        engine->irq_posted = 0;

        if (request)
                request = i915_gem_reset_request(engine, request);

        if (request) {
                DRM_DEBUG_DRIVER("resetting %s to restart from tail of request 0x%x\n",
                                 engine->name, request->global_seqno);
        }

        /* Setup the CS to resume from the breadcrumb of the hung request */
        engine->reset_hw(engine, request);
}

void i915_gem_reset(struct drm_i915_private *dev_priv)
{
        struct intel_engine_cs *engine;
        enum intel_engine_id id;

        lockdep_assert_held(&dev_priv->drm.struct_mutex);

        i915_gem_retire_requests(dev_priv);

        for_each_engine(engine, dev_priv, id) {
                struct i915_gem_context *ctx;

                i915_gem_reset_engine(engine, engine->hangcheck.active_request);
                ctx = fetch_and_zero(&engine->last_retired_context);
                if (ctx)
                        engine->context_unpin(engine, ctx);
        }

        i915_gem_restore_fences(dev_priv);

        if (dev_priv->gt.awake) {
                intel_sanitize_gt_powersave(dev_priv);
                intel_enable_gt_powersave(dev_priv);
                if (INTEL_GEN(dev_priv) >= 6)
                        gen6_rps_busy(dev_priv);
        }
}

void i915_gem_reset_finish_engine(struct intel_engine_cs *engine)
{
        tasklet_enable(&engine->execlists.irq_tasklet);
        kthread_unpark(engine->breadcrumbs.signaler);

        intel_uncore_forcewake_put(engine->i915, FORCEWAKE_ALL);
}

void i915_gem_reset_finish(struct drm_i915_private *dev_priv)
{
        struct intel_engine_cs *engine;
        enum intel_engine_id id;

        lockdep_assert_held(&dev_priv->drm.struct_mutex);

        for_each_engine(engine, dev_priv, id) {
                engine->hangcheck.active_request = NULL;
                i915_gem_reset_finish_engine(engine);
        }
}

static void nop_submit_request(struct drm_i915_gem_request *request)
{
        dma_fence_set_error(&request->fence, -EIO);

        i915_gem_request_submit(request);
}

static void nop_complete_submit_request(struct drm_i915_gem_request *request)
{
        unsigned long flags;

        dma_fence_set_error(&request->fence, -EIO);

        spin_lock_irqsave(&request->engine->timeline->lock, flags);
        __i915_gem_request_submit(request);
        intel_engine_init_global_seqno(request->engine, request->global_seqno);
        spin_unlock_irqrestore(&request->engine->timeline->lock, flags);
}

void i915_gem_set_wedged(struct drm_i915_private *i915)
{
        struct intel_engine_cs *engine;
        enum intel_engine_id id;

        /*
         * First, stop submission to hw, but do not yet complete requests by
         * rolling the global seqno forward (since this would complete requests
         * for which we haven't set the fence error to EIO yet).
         */
        for_each_engine(engine, i915, id)
                engine->submit_request = nop_submit_request;

        /*
         * Make sure no one is running the old callback before we proceed with
         * cancelling requests and resetting the completion tracking. Otherwise
         * we might submit a request to the hardware which never completes.
         */
        synchronize_rcu();

        for_each_engine(engine, i915, id) {
                /* Mark all executing requests as skipped */
                engine->cancel_requests(engine);

                /*
                 * Only once we've force-cancelled all in-flight requests can we
                 * start to complete all requests.
                 */
                engine->submit_request = nop_complete_submit_request;
        }

        /*
         * Make sure no request can slip through without getting completed by
         * either this call here to intel_engine_init_global_seqno, or the one
         * in nop_complete_submit_request.
         */
        synchronize_rcu();

        for_each_engine(engine, i915, id) {
                unsigned long flags;

                /* Mark all pending requests as complete so that any concurrent
                 * (lockless) lookup doesn't try and wait upon the request as we
                 * reset it.
                 */
                spin_lock_irqsave(&engine->timeline->lock, flags);
                intel_engine_init_global_seqno(engine,
                                               intel_engine_last_submit(engine));
                spin_unlock_irqrestore(&engine->timeline->lock, flags);
        }

        set_bit(I915_WEDGED, &i915->gpu_error.flags);
        wake_up_all(&i915->gpu_error.reset_queue);
}

bool i915_gem_unset_wedged(struct drm_i915_private *i915)
{
        struct i915_gem_timeline *tl;
        int i;

        lockdep_assert_held(&i915->drm.struct_mutex);
        if (!test_bit(I915_WEDGED, &i915->gpu_error.flags))
                return true;

        /* Before unwedging, make sure that all pending operations
         * are flushed and errored out - we may have requests waiting upon
         * third party fences. We marked all inflight requests as EIO, and
         * every execbuf since returned EIO, for consistency we want all
         * the currently pending requests to also be marked as EIO, which
         * is done inside our nop_submit_request - and so we must wait.
         *
         * No more can be submitted until we reset the wedged bit.
         */
        list_for_each_entry(tl, &i915->gt.timelines, link) {
                for (i = 0; i < ARRAY_SIZE(tl->engine); i++) {
                        struct drm_i915_gem_request *rq;

                        rq = i915_gem_active_peek(&tl->engine[i].last_request,
                                                  &i915->drm.struct_mutex);
                        if (!rq)
                                continue;

                        /* We can't use our normal waiter as we want to
                         * avoid recursively trying to handle the current
                         * reset. The basic dma_fence_default_wait() installs
                         * a callback for dma_fence_signal(), which is
                         * triggered by our nop handler (indirectly, the
                         * callback enables the signaler thread which is
                         * woken by the nop_submit_request() advancing the seqno
                         * and when the seqno passes the fence, the signaler
                         * then signals the fence waking us up).
                         */
                        if (dma_fence_default_wait(&rq->fence, true,
                                                   MAX_SCHEDULE_TIMEOUT) < 0)
                                return false;
                }
        }

        /* Undo nop_submit_request. We prevent all new i915 requests from
         * being queued (by disallowing execbuf whilst wedged) so having
         * waited for all active requests above, we know the system is idle
         * and do not have to worry about a thread being inside
         * engine->submit_request() as we swap over. So unlike installing
         * the nop_submit_request on reset, we can do this from normal
         * context and do not require stop_machine().
         */
        intel_engines_reset_default_submission(i915);
        i915_gem_contexts_lost(i915);

        smp_mb__before_atomic(); /* complete takeover before enabling execbuf */
        clear_bit(I915_WEDGED, &i915->gpu_error.flags);

        return true;
}

static void
i915_gem_retire_work_handler(struct work_struct *work)
{
        struct drm_i915_private *dev_priv =
                container_of(work, typeof(*dev_priv), gt.retire_work.work);
        struct drm_device *dev = &dev_priv->drm;

        /* Come back later if the device is busy... */
        if (mutex_trylock(&dev->struct_mutex)) {
                i915_gem_retire_requests(dev_priv);
                mutex_unlock(&dev->struct_mutex);
        }

        /* Keep the retire handler running until we are finally idle.
         * We do not need to do this test under locking as in the worst-case
         * we queue the retire worker once too often.
         */
        if (READ_ONCE(dev_priv->gt.awake)) {
                i915_queue_hangcheck(dev_priv);
                queue_delayed_work(dev_priv->wq,
                                   &dev_priv->gt.retire_work,
                                   round_jiffies_up_relative(HZ));
        }
}

static void
i915_gem_idle_work_handler(struct work_struct *work)
{
        struct drm_i915_private *dev_priv =
                container_of(work, typeof(*dev_priv), gt.idle_work.work);
        struct drm_device *dev = &dev_priv->drm;
        bool rearm_hangcheck;

        if (!READ_ONCE(dev_priv->gt.awake))
                return;

        /*
         * Wait for last execlists context complete, but bail out in case a
         * new request is submitted.
         */
        wait_for(intel_engines_are_idle(dev_priv), 10);
        if (READ_ONCE(dev_priv->gt.active_requests))
                return;

        rearm_hangcheck =
                cancel_delayed_work_sync(&dev_priv->gpu_error.hangcheck_work);

        if (!mutex_trylock(&dev->struct_mutex)) {
                /* Currently busy, come back later */
                mod_delayed_work(dev_priv->wq,
                                 &dev_priv->gt.idle_work,
                                 msecs_to_jiffies(50));
                goto out_rearm;
        }

        /*
         * New request retired after this work handler started, extend active
         * period until next instance of the work.
         */
        if (work_pending(work))
                goto out_unlock;

        if (dev_priv->gt.active_requests)
                goto out_unlock;

        if (wait_for(intel_engines_are_idle(dev_priv), 10))
                DRM_ERROR("Timeout waiting for engines to idle\n");

        intel_engines_mark_idle(dev_priv);
        i915_gem_timelines_mark_idle(dev_priv);

        GEM_BUG_ON(!dev_priv->gt.awake);
        dev_priv->gt.awake = false;
        rearm_hangcheck = false;

        if (INTEL_GEN(dev_priv) >= 6)
                gen6_rps_idle(dev_priv);
        intel_runtime_pm_put(dev_priv);
out_unlock:
        mutex_unlock(&dev->struct_mutex);

out_rearm:
        if (rearm_hangcheck) {
                GEM_BUG_ON(!dev_priv->gt.awake);
                i915_queue_hangcheck(dev_priv);
        }
}

void i915_gem_close_object(struct drm_gem_object *gem, struct drm_file *file)
{
        struct drm_i915_private *i915 = to_i915(gem->dev);
        struct drm_i915_gem_object *obj = to_intel_bo(gem);
        struct drm_i915_file_private *fpriv = file->driver_priv;
        struct i915_lut_handle *lut, *ln;

        mutex_lock(&i915->drm.struct_mutex);

        list_for_each_entry_safe(lut, ln, &obj->lut_list, obj_link) {
                struct i915_gem_context *ctx = lut->ctx;
                struct i915_vma *vma;

                GEM_BUG_ON(ctx->file_priv == ERR_PTR(-EBADF));
                if (ctx->file_priv != fpriv)
                        continue;

                vma = radix_tree_delete(&ctx->handles_vma, lut->handle);
                GEM_BUG_ON(vma->obj != obj);

                /* We allow the process to have multiple handles to the same
                 * vma, in the same fd namespace, by virtue of flink/open.
                 */
                GEM_BUG_ON(!vma->open_count);
                if (!--vma->open_count && !i915_vma_is_ggtt(vma))
                        i915_vma_close(vma);

                list_del(&lut->obj_link);
                list_del(&lut->ctx_link);

                kmem_cache_free(i915->luts, lut);
                __i915_gem_object_release_unless_active(obj);
        }

        mutex_unlock(&i915->drm.struct_mutex);
}

static unsigned long to_wait_timeout(s64 timeout_ns)
{
        if (timeout_ns < 0)
                return MAX_SCHEDULE_TIMEOUT;

        if (timeout_ns == 0)
                return 0;

        return nsecs_to_jiffies_timeout(timeout_ns);
}

/**
 * i915_gem_wait_ioctl - implements DRM_IOCTL_I915_GEM_WAIT
 * @dev: drm device pointer
 * @data: ioctl data blob
 * @file: drm file pointer
 *
 * Returns 0 if successful, else an error is returned with the remaining time in
 * the timeout parameter.
 *  -ETIME: object is still busy after timeout
 *  -ERESTARTSYS: signal interrupted the wait
 *  -ENONENT: object doesn't exist
 * Also possible, but rare:
 *  -EAGAIN: incomplete, restart syscall
 *  -ENOMEM: damn
 *  -ENODEV: Internal IRQ fail
 *  -E?: The add request failed
 *
 * The wait ioctl with a timeout of 0 reimplements the busy ioctl. With any
 * non-zero timeout parameter the wait ioctl will wait for the given number of
 * nanoseconds on an object becoming unbusy. Since the wait itself does so
 * without holding struct_mutex the object may become re-busied before this
 * function completes. A similar but shorter * race condition exists in the busy
 * ioctl
 */
int
i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
{
        struct drm_i915_gem_wait *args = data;
        struct drm_i915_gem_object *obj;
        ktime_t start;
        long ret;

        if (args->flags != 0)
                return -EINVAL;

        obj = i915_gem_object_lookup(file, args->bo_handle);
        if (!obj)
                return -ENOENT;

        start = ktime_get();

        ret = i915_gem_object_wait(obj,
                                   I915_WAIT_INTERRUPTIBLE | I915_WAIT_ALL,
                                   to_wait_timeout(args->timeout_ns),
                                   to_rps_client(file));

        if (args->timeout_ns > 0) {
                args->timeout_ns -= ktime_to_ns(ktime_sub(ktime_get(), start));
                if (args->timeout_ns < 0)
                        args->timeout_ns = 0;

                /*
                 * Apparently ktime isn't accurate enough and occasionally has a
                 * bit of mismatch in the jiffies<->nsecs<->ktime loop. So patch
                 * things up to make the test happy. We allow up to 1 jiffy.
                 *
                 * This is a regression from the timespec->ktime conversion.
                 */
                if (ret == -ETIME && !nsecs_to_jiffies(args->timeout_ns))
                        args->timeout_ns = 0;

                /* Asked to wait beyond the jiffie/scheduler precision? */
                if (ret == -ETIME && args->timeout_ns)
                        ret = -EAGAIN;
        }

        i915_gem_object_put(obj);
        return ret;
}

static int wait_for_timeline(struct i915_gem_timeline *tl, unsigned int flags)
{
        int ret, i;

        for (i = 0; i < ARRAY_SIZE(tl->engine); i++) {
                ret = i915_gem_active_wait(&tl->engine[i].last_request, flags);
                if (ret)
                        return ret;
        }

        return 0;
}

static int wait_for_engines(struct drm_i915_private *i915)
{
        if (wait_for(intel_engines_are_idle(i915), 50)) {
                DRM_ERROR("Failed to idle engines, declaring wedged!\n");
                i915_gem_set_wedged(i915);
                return -EIO;
        }

        return 0;
}

int i915_gem_wait_for_idle(struct drm_i915_private *i915, unsigned int flags)
{
        int ret;

        /* If the device is asleep, we have no requests outstanding */
        if (!READ_ONCE(i915->gt.awake))
                return 0;

        if (flags & I915_WAIT_LOCKED) {
                struct i915_gem_timeline *tl;

                lockdep_assert_held(&i915->drm.struct_mutex);

                list_for_each_entry(tl, &i915->gt.timelines, link) {
                        ret = wait_for_timeline(tl, flags);
                        if (ret)
                                return ret;
                }

                i915_gem_retire_requests(i915);
                GEM_BUG_ON(i915->gt.active_requests);

                ret = wait_for_engines(i915);
        } else {
                ret = wait_for_timeline(&i915->gt.global_timeline, flags);
        }

        return ret;
}

static void __i915_gem_object_flush_for_display(struct drm_i915_gem_object *obj)
{
        /*
         * We manually flush the CPU domain so that we can override and
         * force the flush for the display, and perform it asyncrhonously.
         */
        flush_write_domain(obj, ~I915_GEM_DOMAIN_CPU);
        if (obj->cache_dirty)
                i915_gem_clflush_object(obj, I915_CLFLUSH_FORCE);
        obj->base.write_domain = 0;
}

void i915_gem_object_flush_if_display(struct drm_i915_gem_object *obj)
{
        if (!READ_ONCE(obj->pin_global))
                return;

        mutex_lock(&obj->base.dev->struct_mutex);
        __i915_gem_object_flush_for_display(obj);
        mutex_unlock(&obj->base.dev->struct_mutex);
}

/**
 * Moves a single object to the WC read, and possibly write domain.
 * @obj: object to act on
 * @write: ask for write access or read only
 *
 * This function returns when the move is complete, including waiting on
 * flushes to occur.
 */
int
i915_gem_object_set_to_wc_domain(struct drm_i915_gem_object *obj, bool write)
{
        int ret;

        lockdep_assert_held(&obj->base.dev->struct_mutex);

        ret = i915_gem_object_wait(obj,
                                   I915_WAIT_INTERRUPTIBLE |
                                   I915_WAIT_LOCKED |
                                   (write ? I915_WAIT_ALL : 0),
                                   MAX_SCHEDULE_TIMEOUT,
                                   NULL);
        if (ret)
                return ret;

        if (obj->base.write_domain == I915_GEM_DOMAIN_WC)
                return 0;

        /* Flush and acquire obj->pages so that we are coherent through
         * direct access in memory with previous cached writes through
         * shmemfs and that our cache domain tracking remains valid.
         * For example, if the obj->filp was moved to swap without us
         * being notified and releasing the pages, we would mistakenly
         * continue to assume that the obj remained out of the CPU cached
         * domain.
         */
        ret = i915_gem_object_pin_pages(obj);
        if (ret)
                return ret;

        flush_write_domain(obj, ~I915_GEM_DOMAIN_WC);

        /* Serialise direct access to this object with the barriers for
         * coherent writes from the GPU, by effectively invalidating the
         * WC domain upon first access.
         */
        if ((obj->base.read_domains & I915_GEM_DOMAIN_WC) == 0)
                mb();

        /* It should now be out of any other write domains, and we can update
         * the domain values for our changes.
         */
        GEM_BUG_ON((obj->base.write_domain & ~I915_GEM_DOMAIN_WC) != 0);
        obj->base.read_domains |= I915_GEM_DOMAIN_WC;
        if (write) {
                obj->base.read_domains = I915_GEM_DOMAIN_WC;
                obj->base.write_domain = I915_GEM_DOMAIN_WC;
                obj->mm.dirty = true;
        }

        i915_gem_object_unpin_pages(obj);
        return 0;
}

/**
 * Moves a single object to the GTT read, and possibly write domain.
 * @obj: object to act on
 * @write: ask for write access or read only
 *
 * This function returns when the move is complete, including waiting on
 * flushes to occur.
 */
int
i915_gem_object_set_to_gtt_domain(struct drm_i915_gem_object *obj, bool write)
{
        int ret;

        lockdep_assert_held(&obj->base.dev->struct_mutex);

        ret = i915_gem_object_wait(obj,
                                   I915_WAIT_INTERRUPTIBLE |
                                   I915_WAIT_LOCKED |
                                   (write ? I915_WAIT_ALL : 0),
                                   MAX_SCHEDULE_TIMEOUT,
                                   NULL);
        if (ret)
                return ret;

        if (obj->base.write_domain == I915_GEM_DOMAIN_GTT)
                return 0;

        /* Flush and acquire obj->pages so that we are coherent through
         * direct access in memory with previous cached writes through
         * shmemfs and that our cache domain tracking remains valid.
         * For example, if the obj->filp was moved to swap without us
         * being notified and releasing the pages, we would mistakenly
         * continue to assume that the obj remained out of the CPU cached
         * domain.
         */
        ret = i915_gem_object_pin_pages(obj);
        if (ret)
                return ret;

        flush_write_domain(obj, ~I915_GEM_DOMAIN_GTT);

        /* Serialise direct access to this object with the barriers for
         * coherent writes from the GPU, by effectively invalidating the
         * GTT domain upon first access.
         */
        if ((obj->base.read_domains & I915_GEM_DOMAIN_GTT) == 0)
                mb();

        /* It should now be out of any other write domains, and we can update
         * the domain values for our changes.
         */
        GEM_BUG_ON((obj->base.write_domain & ~I915_GEM_DOMAIN_GTT) != 0);
        obj->base.read_domains |= I915_GEM_DOMAIN_GTT;
        if (write) {
                obj->base.read_domains = I915_GEM_DOMAIN_GTT;
                obj->base.write_domain = I915_GEM_DOMAIN_GTT;
                obj->mm.dirty = true;
        }

        i915_gem_object_unpin_pages(obj);
        return 0;
}

/**
 * Changes the cache-level of an object across all VMA.
 * @obj: object to act on
 * @cache_level: new cache level to set for the object
 *
 * After this function returns, the object will be in the new cache-level
 * across all GTT and the contents of the backing storage will be coherent,
 * with respect to the new cache-level. In order to keep the backing storage
 * coherent for all users, we only allow a single cache level to be set
 * globally on the object and prevent it from being changed whilst the
 * hardware is reading from the object. That is if the object is currently
 * on the scanout it will be set to uncached (or equivalent display
 * cache coherency) and all non-MOCS GPU access will also be uncached so
 * that all direct access to the scanout remains coherent.
 */
int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj,
                                    enum i915_cache_level cache_level)
{
        struct i915_vma *vma;
        int ret;

        lockdep_assert_held(&obj->base.dev->struct_mutex);

        if (obj->cache_level == cache_level)
                return 0;

        /* Inspect the list of currently bound VMA and unbind any that would
         * be invalid given the new cache-level. This is principally to
         * catch the issue of the CS prefetch crossing page boundaries and
         * reading an invalid PTE on older architectures.
         */
restart:
        list_for_each_entry(vma, &obj->vma_list, obj_link) {
                if (!drm_mm_node_allocated(&vma->node))
                        continue;

                if (i915_vma_is_pinned(vma)) {
                        DRM_DEBUG("can not change the cache level of pinned objects\n");
                        return -EBUSY;
                }

                if (i915_gem_valid_gtt_space(vma, cache_level))
                        continue;

                ret = i915_vma_unbind(vma);
                if (ret)
                        return ret;

                /* As unbinding may affect other elements in the
                 * obj->vma_list (due to side-effects from retiring
                 * an active vma), play safe and restart the iterator.
                 */
                goto restart;
        }

        /* We can reuse the existing drm_mm nodes but need to change the
         * cache-level on the PTE. We could simply unbind them all and
         * rebind with the correct cache-level on next use. However since
         * we already have a valid slot, dma mapping, pages etc, we may as
         * rewrite the PTE in the belief that doing so tramples upon less
         * state and so involves less work.
         */
        if (obj->bind_count) {
                /* Before we change the PTE, the GPU must not be accessing it.
                 * If we wait upon the object, we know that all the bound
                 * VMA are no longer active.
                 */
                ret = i915_gem_object_wait(obj,
                                           I915_WAIT_INTERRUPTIBLE |
                                           I915_WAIT_LOCKED |
                                           I915_WAIT_ALL,
                                           MAX_SCHEDULE_TIMEOUT,
                                           NULL);
                if (ret)
                        return ret;

                if (!HAS_LLC(to_i915(obj->base.dev)) &&
                    cache_level != I915_CACHE_NONE) {
                        /* Access to snoopable pages through the GTT is
                         * incoherent and on some machines causes a hard
                         * lockup. Relinquish the CPU mmaping to force
                         * userspace to refault in the pages and we can
                         * then double check if the GTT mapping is still
                         * valid for that pointer access.
                         */
                        i915_gem_release_mmap(obj);

                        /* As we no longer need a fence for GTT access,
                         * we can relinquish it now (and so prevent having
                         * to steal a fence from someone else on the next
                         * fence request). Note GPU activity would have
                         * dropped the fence as all snoopable access is
                         * supposed to be linear.
                         */
                        list_for_each_entry(vma, &obj->vma_list, obj_link) {
                                ret = i915_vma_put_fence(vma);
                                if (ret)
                                        return ret;
                        }
                } else {
                        /* We either have incoherent backing store and
                         * so no GTT access or the architecture is fully
                         * coherent. In such cases, existing GTT mmaps
                         * ignore the cache bit in the PTE and we can
                         * rewrite it without confusing the GPU or having
                         * to force userspace to fault back in its mmaps.
                         */
                }

                list_for_each_entry(vma, &obj->vma_list, obj_link) {
                        if (!drm_mm_node_allocated(&vma->node))
                                continue;

                        ret = i915_vma_bind(vma, cache_level, PIN_UPDATE);
                        if (ret)
                                return ret;
                }
        }

        list_for_each_entry(vma, &obj->vma_list, obj_link)
                vma->node.color = cache_level;
        i915_gem_object_set_cache_coherency(obj, cache_level);
        obj->cache_dirty = true; /* Always invalidate stale cachelines */

        return 0;
}

int i915_gem_get_caching_ioctl(struct drm_device *dev, void *data,
                               struct drm_file *file)
{
        struct drm_i915_gem_caching *args = data;
        struct drm_i915_gem_object *obj;
        int err = 0;

        rcu_read_lock();
        obj = i915_gem_object_lookup_rcu(file, args->handle);
        if (!obj) {
                err = -ENOENT;
                goto out;
        }

        switch (obj->cache_level) {
        case I915_CACHE_LLC:
        case I915_CACHE_L3_LLC:
                args->caching = I915_CACHING_CACHED;
                break;

        case I915_CACHE_WT:
                args->caching = I915_CACHING_DISPLAY;
                break;

        default:
                args->caching = I915_CACHING_NONE;
                break;
        }
out:
        rcu_read_unlock();
        return err;
}

int i915_gem_set_caching_ioctl(struct drm_device *dev, void *data,
                               struct drm_file *file)
{
        struct drm_i915_private *i915 = to_i915(dev);
        struct drm_i915_gem_caching *args = data;
        struct drm_i915_gem_object *obj;
        enum i915_cache_level level;
        int ret = 0;

        switch (args->caching) {
        case I915_CACHING_NONE:
                level = I915_CACHE_NONE;
                break;
        case I915_CACHING_CACHED:
                /*
                 * Due to a HW issue on BXT A stepping, GPU stores via a
                 * snooped mapping may leave stale data in a corresponding CPU
                 * cacheline, whereas normally such cachelines would get
                 * invalidated.
                 */
                if (!HAS_LLC(i915) && !HAS_SNOOP(i915))
                        return -ENODEV;

                level = I915_CACHE_LLC;
                break;
        case I915_CACHING_DISPLAY:
                level = HAS_WT(i915) ? I915_CACHE_WT : I915_CACHE_NONE;
                break;
        default:
                return -EINVAL;
        }

        obj = i915_gem_object_lookup(file, args->handle);
        if (!obj)
                return -ENOENT;

        if (obj->cache_level == level)
                goto out;

        ret = i915_gem_object_wait(obj,
                                   I915_WAIT_INTERRUPTIBLE,
                                   MAX_SCHEDULE_TIMEOUT,
                                   to_rps_client(file));
        if (ret)
                goto out;

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

        ret = i915_gem_object_set_cache_level(obj, level);
        mutex_unlock(&dev->struct_mutex);

out:
        i915_gem_object_put(obj);
        return ret;
}

/*
 * Prepare buffer for display plane (scanout, cursors, etc).
 * Can be called from an uninterruptible phase (modesetting) and allows
 * any flushes to be pipelined (for pageflips).
 */
struct i915_vma *
i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
                                     u32 alignment,
                                     const struct i915_ggtt_view *view)
{
        struct i915_vma *vma;
        int ret;

        lockdep_assert_held(&obj->base.dev->struct_mutex);

        /* Mark the global pin early so that we account for the
         * display coherency whilst setting up the cache domains.
         */
        obj->pin_global++;

        /* The display engine is not coherent with the LLC cache on gen6.  As
         * a result, we make sure that the pinning that is about to occur is
         * done with uncached PTEs. This is lowest common denominator for all
         * chipsets.
         *
         * However for gen6+, we could do better by using the GFDT bit instead
         * of uncaching, which would allow us to flush all the LLC-cached data
         * with that bit in the PTE to main memory with just one PIPE_CONTROL.
         */
        ret = i915_gem_object_set_cache_level(obj,
                                              HAS_WT(to_i915(obj->base.dev)) ?
                                              I915_CACHE_WT : I915_CACHE_NONE);
        if (ret) {
                vma = ERR_PTR(ret);
                goto err_unpin_global;
        }

        /* As the user may map the buffer once pinned in the display plane
         * (e.g. libkms for the bootup splash), we have to ensure that we
         * always use map_and_fenceable for all scanout buffers. However,
         * it may simply be too big to fit into mappable, in which case
         * put it anyway and hope that userspace can cope (but always first
         * try to preserve the existing ABI).
         */
        vma = ERR_PTR(-ENOSPC);
        if (!view || view->type == I915_GGTT_VIEW_NORMAL)
                vma = i915_gem_object_ggtt_pin(obj, view, 0, alignment,
                                               PIN_MAPPABLE | PIN_NONBLOCK);
        if (IS_ERR(vma)) {
                struct drm_i915_private *i915 = to_i915(obj->base.dev);
                unsigned int flags;

                /* Valleyview is definitely limited to scanning out the first
                 * 512MiB. Lets presume this behaviour was inherited from the
                 * g4x display engine and that all earlier gen are similarly
                 * limited. Testing suggests that it is a little more
                 * complicated than this. For example, Cherryview appears quite
                 * happy to scanout from anywhere within its global aperture.
                 */
                flags = 0;
                if (HAS_GMCH_DISPLAY(i915))
                        flags = PIN_MAPPABLE;
                vma = i915_gem_object_ggtt_pin(obj, view, 0, alignment, flags);
        }
        if (IS_ERR(vma))
                goto err_unpin_global;

        vma->display_alignment = max_t(u64, vma->display_alignment, alignment);

        /* Treat this as an end-of-frame, like intel_user_framebuffer_dirty() */
        __i915_gem_object_flush_for_display(obj);
        intel_fb_obj_flush(obj, ORIGIN_DIRTYFB);

        /* It should now be out of any other write domains, and we can update
         * the domain values for our changes.
         */
        obj->base.read_domains |= I915_GEM_DOMAIN_GTT;

        return vma;

err_unpin_global:
        obj->pin_global--;
        return vma;
}

void
i915_gem_object_unpin_from_display_plane(struct i915_vma *vma)
{
        lockdep_assert_held(&vma->vm->i915->drm.struct_mutex);

        if (WARN_ON(vma->obj->pin_global == 0))
                return;

        if (--vma->obj->pin_global == 0)
                vma->display_alignment = I915_GTT_MIN_ALIGNMENT;

        /* Bump the LRU to try and avoid premature eviction whilst flipping  */
        i915_gem_object_bump_inactive_ggtt(vma->obj);

        i915_vma_unpin(vma);
}

/**
 * Moves a single object to the CPU read, and possibly write domain.
 * @obj: object to act on
 * @write: requesting write or read-only access
 *
 * This function returns when the move is complete, including waiting on
 * flushes to occur.
 */
int
i915_gem_object_set_to_cpu_domain(struct drm_i915_gem_object *obj, bool write)
{
        int ret;

        lockdep_assert_held(&obj->base.dev->struct_mutex);

        ret = i915_gem_object_wait(obj,
                                   I915_WAIT_INTERRUPTIBLE |
                                   I915_WAIT_LOCKED |
                                   (write ? I915_WAIT_ALL : 0),
                                   MAX_SCHEDULE_TIMEOUT,
                                   NULL);
        if (ret)
                return ret;

        flush_write_domain(obj, ~I915_GEM_DOMAIN_CPU);

        /* Flush the CPU cache if it's still invalid. */
        if ((obj->base.read_domains & I915_GEM_DOMAIN_CPU) == 0) {
                i915_gem_clflush_object(obj, I915_CLFLUSH_SYNC);
                obj->base.read_domains |= I915_GEM_DOMAIN_CPU;
        }

        /* It should now be out of any other write domains, and we can update
         * the domain values for our changes.
         */
        GEM_BUG_ON(obj->base.write_domain & ~I915_GEM_DOMAIN_CPU);

        /* If we're writing through the CPU, then the GPU read domains will
         * need to be invalidated at next use.
         */
        if (write)
                __start_cpu_write(obj);

        return 0;
}

/* Throttle our rendering by waiting until the ring has completed our requests
 * emitted over 20 msec ago.
 *
 * Note that if we were to use the current jiffies each time around the loop,
 * we wouldn't escape the function with any frames outstanding if the time to
 * render a frame was over 20ms.
 *
 * This should get us reasonable parallelism between CPU and GPU but also
 * relatively low latency when blocking on a particular request to finish.
 */
static int
i915_gem_ring_throttle(struct drm_device *dev, struct drm_file *file)
{
        struct drm_i915_private *dev_priv = to_i915(dev);
        struct drm_i915_file_private *file_priv = file->driver_priv;
        unsigned long recent_enough = jiffies - DRM_I915_THROTTLE_JIFFIES;
        struct drm_i915_gem_request *request, *target = NULL;
        long ret;

        /* ABI: return -EIO if already wedged */
        if (i915_terminally_wedged(&dev_priv->gpu_error))
                return -EIO;

        spin_lock(&file_priv->mm.lock);
        list_for_each_entry(request, &file_priv->mm.request_list, client_link) {
                if (time_after_eq(request->emitted_jiffies, recent_enough))
                        break;

                if (target) {
                        list_del(&target->client_link);
                        target->file_priv = NULL;
                }

                target = request;
        }
        if (target)
                i915_gem_request_get(target);
        spin_unlock(&file_priv->mm.lock);

        if (target == NULL)
                return 0;

        ret = i915_wait_request(target,
                                I915_WAIT_INTERRUPTIBLE,
                                MAX_SCHEDULE_TIMEOUT);
        i915_gem_request_put(target);

        return ret < 0 ? ret : 0;
}

struct i915_vma *
i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
                         const struct i915_ggtt_view *view,
                         u64 size,
                         u64 alignment,
                         u64 flags)
{
        struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
        struct i915_address_space *vm = &dev_priv->ggtt.base;
        struct i915_vma *vma;
        int ret;

        lockdep_assert_held(&obj->base.dev->struct_mutex);

        if (!view && flags & PIN_MAPPABLE) {
                /* If the required space is larger than the available
                 * aperture, we will not able to find a slot for the
                 * object and unbinding the object now will be in
                 * vain. Worse, doing so may cause us to ping-pong
                 * the object in and out of the Global GTT and
                 * waste a lot of cycles under the mutex.
                 */
                if (obj->base.size > dev_priv->ggtt.mappable_end)
                        return ERR_PTR(-E2BIG);

                /* If NONBLOCK is set the caller is optimistically
                 * trying to cache the full object within the mappable
                 * aperture, and *must* have a fallback in place for
                 * situations where we cannot bind the object. We
                 * can be a little more lax here and use the fallback
                 * more often to avoid costly migrations of ourselves
                 * and other objects within the aperture.
                 *
                 * Half-the-aperture is used as a simple heuristic.
                 * More interesting would to do search for a free
                 * block prior to making the commitment to unbind.
                 * That caters for the self-harm case, and with a
                 * little more heuristics (e.g. NOFAULT, NOEVICT)
                 * we could try to minimise harm to others.
                 */
                if (flags & PIN_NONBLOCK &&
                    obj->base.size > dev_priv->ggtt.mappable_end / 2)
                        return ERR_PTR(-ENOSPC);
        }

        vma = i915_vma_instance(obj, vm, view);
        if (unlikely(IS_ERR(vma)))
                return vma;

        if (i915_vma_misplaced(vma, size, alignment, flags)) {
                if (flags & PIN_NONBLOCK) {
                        if (i915_vma_is_pinned(vma) || i915_vma_is_active(vma))
                                return ERR_PTR(-ENOSPC);

                        if (flags & PIN_MAPPABLE &&
                            vma->fence_size > dev_priv->ggtt.mappable_end / 2)
                                return ERR_PTR(-ENOSPC);
                }

                WARN(i915_vma_is_pinned(vma),
                     "bo is already pinned in ggtt with incorrect alignment:"
                     " offset=%08x, req.alignment=%llx,"
                     " req.map_and_fenceable=%d, vma->map_and_fenceable=%d\n",
                     i915_ggtt_offset(vma), alignment,
                     !!(flags & PIN_MAPPABLE),
                     i915_vma_is_map_and_fenceable(vma));
                ret = i915_vma_unbind(vma);
                if (ret)
                        return ERR_PTR(ret);
        }

        ret = i915_vma_pin(vma, size, alignment, flags | PIN_GLOBAL);
        if (ret)
                return ERR_PTR(ret);

        return vma;
}

static __always_inline unsigned int __busy_read_flag(unsigned int id)
{
        /* Note that we could alias engines in the execbuf API, but
         * that would be very unwise as it prevents userspace from
         * fine control over engine selection. Ahem.
         *
         * This should be something like EXEC_MAX_ENGINE instead of
         * I915_NUM_ENGINES.
         */
        BUILD_BUG_ON(I915_NUM_ENGINES > 16);
        return 0x10000 << id;
}

static __always_inline unsigned int __busy_write_id(unsigned int id)
{
        /* The uABI guarantees an active writer is also amongst the read
         * engines. This would be true if we accessed the activity tracking
         * under the lock, but as we perform the lookup of the object and
         * its activity locklessly we can not guarantee that the last_write
         * being active implies that we have set the same engine flag from
         * last_read - hence we always set both read and write busy for
         * last_write.
         */
        return id | __busy_read_flag(id);
}

static __always_inline unsigned int
__busy_set_if_active(const struct dma_fence *fence,
                     unsigned int (*flag)(unsigned int id))
{
        struct drm_i915_gem_request *rq;

        /* We have to check the current hw status of the fence as the uABI
         * guarantees forward progress. We could rely on the idle worker
         * to eventually flush us, but to minimise latency just ask the
         * hardware.
         *
         * Note we only report on the status of native fences.
         */
        if (!dma_fence_is_i915(fence))
                return 0;

        /* opencode to_request() in order to avoid const warnings */
        rq = container_of(fence, struct drm_i915_gem_request, fence);
        if (i915_gem_request_completed(rq))
                return 0;

        return flag(rq->engine->uabi_id);
}

static __always_inline unsigned int
busy_check_reader(const struct dma_fence *fence)
{
        return __busy_set_if_active(fence, __busy_read_flag);
}

static __always_inline unsigned int
busy_check_writer(const struct dma_fence *fence)
{
        if (!fence)
                return 0;

        return __busy_set_if_active(fence, __busy_write_id);
}

int
i915_gem_busy_ioctl(struct drm_device *dev, void *data,
                    struct drm_file *file)
{
        struct drm_i915_gem_busy *args = data;
        struct drm_i915_gem_object *obj;
        struct reservation_object_list *list;
        unsigned int seq;
        int err;

        err = -ENOENT;
        rcu_read_lock();
        obj = i915_gem_object_lookup_rcu(file, args->handle);
        if (!obj)
                goto out;

        /* A discrepancy here is that we do not report the status of
         * non-i915 fences, i.e. even though we may report the object as idle,
         * a call to set-domain may still stall waiting for foreign rendering.
         * This also means that wait-ioctl may report an object as busy,
         * where busy-ioctl considers it idle.
         *
         * We trade the ability to warn of foreign fences to report on which
         * i915 engines are active for the object.
         *
         * Alternatively, we can trade that extra information on read/write
         * activity with
         *      args->busy =
         *              !reservation_object_test_signaled_rcu(obj->resv, true);
         * to report the overall busyness. This is what the wait-ioctl does.
         *
         */
retry:
        seq = raw_read_seqcount(&obj->resv->seq);

        /* Translate the exclusive fence to the READ *and* WRITE engine */
        args->busy = busy_check_writer(rcu_dereference(obj->resv->fence_excl));

        /* Translate shared fences to READ set of engines */
        list = rcu_dereference(obj->resv->fence);
        if (list) {
                unsigned int shared_count = list->shared_count, i;

                for (i = 0; i < shared_count; ++i) {
                        struct dma_fence *fence =
                                rcu_dereference(list->shared[i]);

                        args->busy |= busy_check_reader(fence);
                }
        }

        if (args->busy && read_seqcount_retry(&obj->resv->seq, seq))
                goto retry;

        err = 0;
out:
        rcu_read_unlock();
        return err;
}

int
i915_gem_throttle_ioctl(struct drm_device *dev, void *data,
                        struct drm_file *file_priv)
{
        return i915_gem_ring_throttle(dev, file_priv);
}

int
i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
                       struct drm_file *file_priv)
{
        struct drm_i915_private *dev_priv = to_i915(dev);
        struct drm_i915_gem_madvise *args = data;
        struct drm_i915_gem_object *obj;
        int err;

        switch (args->madv) {
        case I915_MADV_DONTNEED:
        case I915_MADV_WILLNEED:
            break;
        default:
            return -EINVAL;
        }

        obj = i915_gem_object_lookup(file_priv, args->handle);
        if (!obj)
                return -ENOENT;

        err = mutex_lock_interruptible(&obj->mm.lock);
        if (err)
                goto out;

        if (i915_gem_object_has_pages(obj) &&
            i915_gem_object_is_tiled(obj) &&
            dev_priv->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
                if (obj->mm.madv == I915_MADV_WILLNEED) {
                        GEM_BUG_ON(!obj->mm.quirked);
                        __i915_gem_object_unpin_pages(obj);
                        obj->mm.quirked = false;
                }
                if (args->madv == I915_MADV_WILLNEED) {
                        GEM_BUG_ON(obj->mm.quirked);
                        __i915_gem_object_pin_pages(obj);
                        obj->mm.quirked = true;
                }
        }

        if (obj->mm.madv != __I915_MADV_PURGED)
                obj->mm.madv = args->madv;

        /* if the object is no longer attached, discard its backing storage */
        if (obj->mm.madv == I915_MADV_DONTNEED &&
            !i915_gem_object_has_pages(obj))
                i915_gem_object_truncate(obj);

        args->retained = obj->mm.madv != __I915_MADV_PURGED;
        mutex_unlock(&obj->mm.lock);

out:
        i915_gem_object_put(obj);
        return err;
}

static void
frontbuffer_retire(struct i915_gem_active *active,
                   struct drm_i915_gem_request *request)
{
        struct drm_i915_gem_object *obj =
                container_of(active, typeof(*obj), frontbuffer_write);

        intel_fb_obj_flush(obj, ORIGIN_CS);
}

void i915_gem_object_init(struct drm_i915_gem_object *obj,
                          const struct drm_i915_gem_object_ops *ops)
{
        mutex_init(&obj->mm.lock);

        INIT_LIST_HEAD(&obj->vma_list);
        INIT_LIST_HEAD(&obj->lut_list);
        INIT_LIST_HEAD(&obj->batch_pool_link);

        obj->ops = ops;

        reservation_object_init(&obj->__builtin_resv);
        obj->resv = &obj->__builtin_resv;

        obj->frontbuffer_ggtt_origin = ORIGIN_GTT;
        init_request_active(&obj->frontbuffer_write, frontbuffer_retire);

        obj->mm.madv = I915_MADV_WILLNEED;
        INIT_RADIX_TREE(&obj->mm.get_page.radix, GFP_KERNEL | __GFP_NOWARN);
        mutex_init(&obj->mm.get_page.lock);

        i915_gem_info_add_obj(to_i915(obj->base.dev), obj->base.size);
}

static const struct drm_i915_gem_object_ops i915_gem_object_ops = {
        .flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE |
                 I915_GEM_OBJECT_IS_SHRINKABLE,

        .get_pages = i915_gem_object_get_pages_gtt,
        .put_pages = i915_gem_object_put_pages_gtt,

        .pwrite = i915_gem_object_pwrite_gtt,
};

static int i915_gem_object_create_shmem(struct drm_device *dev,
                                        struct drm_gem_object *obj,
                                        size_t size)
{
        struct drm_i915_private *i915 = to_i915(dev);
        unsigned long flags = VM_NORESERVE;
        struct file *filp;

        drm_gem_private_object_init(dev, obj, size);

        if (i915->mm.gemfs)
                filp = shmem_file_setup_with_mnt(i915->mm.gemfs, "i915", size,
                                                 flags);
        else
                filp = shmem_file_setup("i915", size, flags);

        if (IS_ERR(filp))
                return PTR_ERR(filp);

        obj->filp = filp;

        return 0;
}

struct drm_i915_gem_object *
i915_gem_object_create(struct drm_i915_private *dev_priv, u64 size)
{
        struct drm_i915_gem_object *obj;
        struct address_space *mapping;
        unsigned int cache_level;
        gfp_t mask;
        int ret;

        /* There is a prevalence of the assumption that we fit the object's
         * page count inside a 32bit _signed_ variable. Let's document this and
         * catch if we ever need to fix it. In the meantime, if you do spot
         * such a local variable, please consider fixing!
         */
        if (size >> PAGE_SHIFT > INT_MAX)
                return ERR_PTR(-E2BIG);

        if (overflows_type(size, obj->base.size))
                return ERR_PTR(-E2BIG);

        obj = i915_gem_object_alloc(dev_priv);
        if (obj == NULL)
                return ERR_PTR(-ENOMEM);

        ret = i915_gem_object_create_shmem(&dev_priv->drm, &obj->base, size);
        if (ret)
                goto fail;

        mask = GFP_HIGHUSER | __GFP_RECLAIMABLE;
        if (IS_I965GM(dev_priv) || IS_I965G(dev_priv)) {
                /* 965gm cannot relocate objects above 4GiB. */
                mask &= ~__GFP_HIGHMEM;
                mask |= __GFP_DMA32;
        }

        mapping = obj->base.filp->f_mapping;
        mapping_set_gfp_mask(mapping, mask);
        GEM_BUG_ON(!(mapping_gfp_mask(mapping) & __GFP_RECLAIM));

        i915_gem_object_init(obj, &i915_gem_object_ops);

        obj->base.write_domain = I915_GEM_DOMAIN_CPU;
        obj->base.read_domains = I915_GEM_DOMAIN_CPU;

        if (HAS_LLC(dev_priv))
                /* On some devices, we can have the GPU use the LLC (the CPU
                 * cache) for about a 10% performance improvement
                 * compared to uncached.  Graphics requests other than
                 * display scanout are coherent with the CPU in
                 * accessing this cache.  This means in this mode we
                 * don't need to clflush on the CPU side, and on the
                 * GPU side we only need to flush internal caches to
                 * get data visible to the CPU.
                 *
                 * However, we maintain the display planes as UC, and so
                 * need to rebind when first used as such.
                 */
                cache_level = I915_CACHE_LLC;
        else
                cache_level = I915_CACHE_NONE;

        i915_gem_object_set_cache_coherency(obj, cache_level);

        trace_i915_gem_object_create(obj);

        return obj;

fail:
        i915_gem_object_free(obj);
        return ERR_PTR(ret);
}

static bool discard_backing_storage(struct drm_i915_gem_object *obj)
{
        /* If we are the last user of the backing storage (be it shmemfs
         * pages or stolen etc), we know that the pages are going to be
         * immediately released. In this case, we can then skip copying
         * back the contents from the GPU.
         */

        if (obj->mm.madv != I915_MADV_WILLNEED)
                return false;

        if (obj->base.filp == NULL)
                return true;

        /* At first glance, this looks racy, but then again so would be
         * userspace racing mmap against close. However, the first external
         * reference to the filp can only be obtained through the
         * i915_gem_mmap_ioctl() which safeguards us against the user
         * acquiring such a reference whilst we are in the middle of
         * freeing the object.
         */
        return atomic_long_read(&obj->base.filp->f_count) == 1;
}

static void __i915_gem_free_objects(struct drm_i915_private *i915,
                                    struct llist_node *freed)
{
        struct drm_i915_gem_object *obj, *on;

        intel_runtime_pm_get(i915);
        llist_for_each_entry_safe(obj, on, freed, freed) {
                struct i915_vma *vma, *vn;

                trace_i915_gem_object_destroy(obj);

                mutex_lock(&i915->drm.struct_mutex);

                GEM_BUG_ON(i915_gem_object_is_active(obj));
                list_for_each_entry_safe(vma, vn,
                                         &obj->vma_list, obj_link) {
                        GEM_BUG_ON(i915_vma_is_active(vma));
                        vma->flags &= ~I915_VMA_PIN_MASK;
                        i915_vma_close(vma);
                }
                GEM_BUG_ON(!list_empty(&obj->vma_list));
                GEM_BUG_ON(!RB_EMPTY_ROOT(&obj->vma_tree));

                /* This serializes freeing with the shrinker. Since the free
                 * is delayed, first by RCU then by the workqueue, we want the
                 * shrinker to be able to free pages of unreferenced objects,
                 * or else we may oom whilst there are plenty of deferred
                 * freed objects.
                 */
                if (i915_gem_object_has_pages(obj)) {
                        spin_lock(&i915->mm.obj_lock);
                        list_del_init(&obj->mm.link);
                        spin_unlock(&i915->mm.obj_lock);
                }

                mutex_unlock(&i915->drm.struct_mutex);

                GEM_BUG_ON(obj->bind_count);
                GEM_BUG_ON(obj->userfault_count);
                GEM_BUG_ON(atomic_read(&obj->frontbuffer_bits));
                GEM_BUG_ON(!list_empty(&obj->lut_list));

                if (obj->ops->release)
                        obj->ops->release(obj);

                if (WARN_ON(i915_gem_object_has_pinned_pages(obj)))
                        atomic_set(&obj->mm.pages_pin_count, 0);
                __i915_gem_object_put_pages(obj, I915_MM_NORMAL);
                GEM_BUG_ON(i915_gem_object_has_pages(obj));

                if (obj->base.import_attach)
                        drm_prime_gem_destroy(&obj->base, NULL);

                reservation_object_fini(&obj->__builtin_resv);
                drm_gem_object_release(&obj->base);
                i915_gem_info_remove_obj(i915, obj->base.size);

                kfree(obj->bit_17);
                i915_gem_object_free(obj);

                if (on)
                        cond_resched();
        }
        intel_runtime_pm_put(i915);
}

static void i915_gem_flush_free_objects(struct drm_i915_private *i915)
{
        struct llist_node *freed;

        /* Free the oldest, most stale object to keep the free_list short */
        freed = NULL;
        if (!llist_empty(&i915->mm.free_list)) { /* quick test for hotpath */
                /* Only one consumer of llist_del_first() allowed */
                spin_lock(&i915->mm.free_lock);
                freed = llist_del_first(&i915->mm.free_list);
                spin_unlock(&i915->mm.free_lock);
        }
        if (unlikely(freed)) {
                freed->next = NULL;
                __i915_gem_free_objects(i915, freed);
        }
}

static void __i915_gem_free_work(struct work_struct *work)
{
        struct drm_i915_private *i915 =
                container_of(work, struct drm_i915_private, mm.free_work);
        struct llist_node *freed;

        /* All file-owned VMA should have been released by this point through
         * i915_gem_close_object(), or earlier by i915_gem_context_close().
         * However, the object may also be bound into the global GTT (e.g.
         * older GPUs without per-process support, or for direct access through
         * the GTT either for the user or for scanout). Those VMA still need to
         * unbound now.
         */

        spin_lock(&i915->mm.free_lock);
        while ((freed = llist_del_all(&i915->mm.free_list))) {
                spin_unlock(&i915->mm.free_lock);

                __i915_gem_free_objects(i915, freed);
                if (need_resched())
                        return;

                spin_lock(&i915->mm.free_lock);
        }
        spin_unlock(&i915->mm.free_lock);
}

static void __i915_gem_free_object_rcu(struct rcu_head *head)
{
        struct drm_i915_gem_object *obj =
                container_of(head, typeof(*obj), rcu);
        struct drm_i915_private *i915 = to_i915(obj->base.dev);

        /* We can't simply use call_rcu() from i915_gem_free_object()
         * as we need to block whilst unbinding, and the call_rcu
         * task may be called from softirq context. So we take a
         * detour through a worker.
         */
        if (llist_add(&obj->freed, &i915->mm.free_list))
                schedule_work(&i915->mm.free_work);
}

void i915_gem_free_object(struct drm_gem_object *gem_obj)
{
        struct drm_i915_gem_object *obj = to_intel_bo(gem_obj);

        if (obj->mm.quirked)
                __i915_gem_object_unpin_pages(obj);

        if (discard_backing_storage(obj))
                obj->mm.madv = I915_MADV_DONTNEED;

        /* Before we free the object, make sure any pure RCU-only
         * read-side critical sections are complete, e.g.
         * i915_gem_busy_ioctl(). For the corresponding synchronized
         * lookup see i915_gem_object_lookup_rcu().
         */
        call_rcu(&obj->rcu, __i915_gem_free_object_rcu);
}

void __i915_gem_object_release_unless_active(struct drm_i915_gem_object *obj)
{
        lockdep_assert_held(&obj->base.dev->struct_mutex);

        if (!i915_gem_object_has_active_reference(obj) &&
            i915_gem_object_is_active(obj))
                i915_gem_object_set_active_reference(obj);
        else
                i915_gem_object_put(obj);
}

static void assert_kernel_context_is_current(struct drm_i915_private *dev_priv)
{
        struct intel_engine_cs *engine;
        enum intel_engine_id id;

        for_each_engine(engine, dev_priv, id)
                GEM_BUG_ON(engine->last_retired_context &&
                           !i915_gem_context_is_kernel(engine->last_retired_context));
}

void i915_gem_sanitize(struct drm_i915_private *i915)
{
        if (i915_terminally_wedged(&i915->gpu_error)) {
                mutex_lock(&i915->drm.struct_mutex);
                i915_gem_unset_wedged(i915);
                mutex_unlock(&i915->drm.struct_mutex);
        }

        /*
         * If we inherit context state from the BIOS or earlier occupants
         * of the GPU, the GPU may be in an inconsistent state when we
         * try to take over. The only way to remove the earlier state
         * is by resetting. However, resetting on earlier gen is tricky as
         * it may impact the display and we are uncertain about the stability
         * of the reset, so this could be applied to even earlier gen.
         */
        if (INTEL_GEN(i915) >= 5) {
                int reset = intel_gpu_reset(i915, ALL_ENGINES);
                WARN_ON(reset && reset != -ENODEV);
        }
}

int i915_gem_suspend(struct drm_i915_private *dev_priv)
{
        struct drm_device *dev = &dev_priv->drm;
        int ret;

        intel_runtime_pm_get(dev_priv);
        intel_suspend_gt_powersave(dev_priv);

        mutex_lock(&dev->struct_mutex);

        /* We have to flush all the executing contexts to main memory so
         * that they can saved in the hibernation image. To ensure the last
         * context image is coherent, we have to switch away from it. That
         * leaves the dev_priv->kernel_context still active when
         * we actually suspend, and its image in memory may not match the GPU
         * state. Fortunately, the kernel_context is disposable and we do
         * not rely on its state.
         */
        if (!i915_terminally_wedged(&dev_priv->gpu_error)) {
                ret = i915_gem_switch_to_kernel_context(dev_priv);
                if (ret)
                        goto err_unlock;

                ret = i915_gem_wait_for_idle(dev_priv,
                                             I915_WAIT_INTERRUPTIBLE |
                                             I915_WAIT_LOCKED);
                if (ret && ret != -EIO)
                        goto err_unlock;

                assert_kernel_context_is_current(dev_priv);
        }
        i915_gem_contexts_lost(dev_priv);
        mutex_unlock(&dev->struct_mutex);

        intel_guc_suspend(dev_priv);

        cancel_delayed_work_sync(&dev_priv->gpu_error.hangcheck_work);
        cancel_delayed_work_sync(&dev_priv->gt.retire_work);

        /* As the idle_work is rearming if it detects a race, play safe and
         * repeat the flush until it is definitely idle.
         */
        drain_delayed_work(&dev_priv->gt.idle_work);

        /* Assert that we sucessfully flushed all the work and
         * reset the GPU back to its idle, low power state.
         */
        WARN_ON(dev_priv->gt.awake);
        if (WARN_ON(!intel_engines_are_idle(dev_priv)))
                i915_gem_set_wedged(dev_priv); /* no hope, discard everything */

        /*
         * Neither the BIOS, ourselves or any other kernel
         * expects the system to be in execlists mode on startup,
         * so we need to reset the GPU back to legacy mode. And the only
         * known way to disable logical contexts is through a GPU reset.
         *
         * So in order to leave the system in a known default configuration,
         * always reset the GPU upon unload and suspend. Afterwards we then
         * clean up the GEM state tracking, flushing off the requests and
         * leaving the system in a known idle state.
         *
         * Note that is of the upmost importance that the GPU is idle and
         * all stray writes are flushed *before* we dismantle the backing
         * storage for the pinned objects.
         *
         * However, since we are uncertain that resetting the GPU on older
         * machines is a good idea, we don't - just in case it leaves the
         * machine in an unusable condition.
         */
        i915_gem_sanitize(dev_priv);

        intel_runtime_pm_put(dev_priv);
        return 0;

err_unlock:
        mutex_unlock(&dev->struct_mutex);
        intel_runtime_pm_put(dev_priv);
        return ret;
}

void i915_gem_resume(struct drm_i915_private *dev_priv)
{
        struct drm_device *dev = &dev_priv->drm;

        WARN_ON(dev_priv->gt.awake);

        mutex_lock(&dev->struct_mutex);
        i915_gem_restore_gtt_mappings(dev_priv);
        i915_gem_restore_fences(dev_priv);

        /* As we didn't flush the kernel context before suspend, we cannot
         * guarantee that the context image is complete. So let's just reset
         * it and start again.
         */
        dev_priv->gt.resume(dev_priv);

        mutex_unlock(&dev->struct_mutex);
}

void i915_gem_init_swizzling(struct drm_i915_private *dev_priv)
{
        if (INTEL_GEN(dev_priv) < 5 ||
            dev_priv->mm.bit_6_swizzle_x == I915_BIT_6_SWIZZLE_NONE)
                return;

        I915_WRITE(DISP_ARB_CTL, I915_READ(DISP_ARB_CTL) |
                                 DISP_TILE_SURFACE_SWIZZLING);

        if (IS_GEN5(dev_priv))
                return;

        I915_WRITE(TILECTL, I915_READ(TILECTL) | TILECTL_SWZCTL);
        if (IS_GEN6(dev_priv))
                I915_WRITE(ARB_MODE, _MASKED_BIT_ENABLE(ARB_MODE_SWIZZLE_SNB));
        else if (IS_GEN7(dev_priv))
                I915_WRITE(ARB_MODE, _MASKED_BIT_ENABLE(ARB_MODE_SWIZZLE_IVB));
        else if (IS_GEN8(dev_priv))
                I915_WRITE(GAMTARBMODE, _MASKED_BIT_ENABLE(ARB_MODE_SWIZZLE_BDW));
        else
                BUG();
}

static void init_unused_ring(struct drm_i915_private *dev_priv, u32 base)
{
        I915_WRITE(RING_CTL(base), 0);
        I915_WRITE(RING_HEAD(base), 0);
        I915_WRITE(RING_TAIL(base), 0);
        I915_WRITE(RING_START(base), 0);
}

static void init_unused_rings(struct drm_i915_private *dev_priv)
{
        if (IS_I830(dev_priv)) {
                init_unused_ring(dev_priv, PRB1_BASE);
                init_unused_ring(dev_priv, SRB0_BASE);
                init_unused_ring(dev_priv, SRB1_BASE);
                init_unused_ring(dev_priv, SRB2_BASE);
                init_unused_ring(dev_priv, SRB3_BASE);
        } else if (IS_GEN2(dev_priv)) {
                init_unused_ring(dev_priv, SRB0_BASE);
                init_unused_ring(dev_priv, SRB1_BASE);
        } else if (IS_GEN3(dev_priv)) {
                init_unused_ring(dev_priv, PRB1_BASE);
                init_unused_ring(dev_priv, PRB2_BASE);
        }
}

static int __i915_gem_restart_engines(void *data)
{
        struct drm_i915_private *i915 = data;
        struct intel_engine_cs *engine;
        enum intel_engine_id id;
        int err;

        for_each_engine(engine, i915, id) {
                err = engine->init_hw(engine);
                if (err)
                        return err;
        }

        return 0;
}

int i915_gem_init_hw(struct drm_i915_private *dev_priv)
{
        int ret;

        dev_priv->gt.last_init_time = ktime_get();

        /* Double layer security blanket, see i915_gem_init() */
        intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);

        if (HAS_EDRAM(dev_priv) && INTEL_GEN(dev_priv) < 9)
                I915_WRITE(HSW_IDICR, I915_READ(HSW_IDICR) | IDIHASHMSK(0xf));

        if (IS_HASWELL(dev_priv))
                I915_WRITE(MI_PREDICATE_RESULT_2, IS_HSW_GT3(dev_priv) ?
                           LOWER_SLICE_ENABLED : LOWER_SLICE_DISABLED);

        if (HAS_PCH_NOP(dev_priv)) {
                if (IS_IVYBRIDGE(dev_priv)) {
                        u32 temp = I915_READ(GEN7_MSG_CTL);
                        temp &= ~(WAIT_FOR_PCH_FLR_ACK | WAIT_FOR_PCH_RESET_ACK);
                        I915_WRITE(GEN7_MSG_CTL, temp);
                } else if (INTEL_GEN(dev_priv) >= 7) {
                        u32 temp = I915_READ(HSW_NDE_RSTWRN_OPT);
                        temp &= ~RESET_PCH_HANDSHAKE_ENABLE;
                        I915_WRITE(HSW_NDE_RSTWRN_OPT, temp);
                }
        }

        i915_gem_init_swizzling(dev_priv);

        /*
         * At least 830 can leave some of the unused rings
         * "active" (ie. head != tail) after resume which
         * will prevent c3 entry. Makes sure all unused rings
         * are totally idle.
         */
        init_unused_rings(dev_priv);

        BUG_ON(!dev_priv->kernel_context);
        if (i915_terminally_wedged(&dev_priv->gpu_error)) {
                ret = -EIO;
                goto out;
        }

        ret = i915_ppgtt_init_hw(dev_priv);
        if (ret) {
                DRM_ERROR("PPGTT enable HW failed %d\n", ret);
                goto out;
        }

        /* Need to do basic initialisation of all rings first: */
        ret = __i915_gem_restart_engines(dev_priv);
        if (ret)
                goto out;

        intel_mocs_init_l3cc_table(dev_priv);

        /* We can't enable contexts until all firmware is loaded */
        ret = intel_uc_init_hw(dev_priv);
        if (ret)
                goto out;

out:
        intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
        return ret;
}

bool intel_sanitize_semaphores(struct drm_i915_private *dev_priv, int value)
{
        if (INTEL_INFO(dev_priv)->gen < 6)
                return false;

        /* TODO: make semaphores and Execlists play nicely together */
        if (i915_modparams.enable_execlists)
                return false;

        if (value >= 0)
                return value;

        /* Enable semaphores on SNB when IO remapping is off */
        if (IS_GEN6(dev_priv) && intel_vtd_active())
                return false;

        return true;
}

int i915_gem_init(struct drm_i915_private *dev_priv)
{
        int ret;

        /*
         * We need to fallback to 4K pages since gvt gtt handling doesn't
         * support huge page entries - we will need to check either hypervisor
         * mm can support huge guest page or just do emulation in gvt.
         */
        if (intel_vgpu_active(dev_priv))
                mkwrite_device_info(dev_priv)->page_sizes =
                        I915_GTT_PAGE_SIZE_4K;

        dev_priv->mm.unordered_timeline = dma_fence_context_alloc(1);

        if (!i915_modparams.enable_execlists) {
                dev_priv->gt.resume = intel_legacy_submission_resume;
                dev_priv->gt.cleanup_engine = intel_engine_cleanup;
        } else {
                dev_priv->gt.resume = intel_lr_context_resume;
                dev_priv->gt.cleanup_engine = intel_logical_ring_cleanup;
        }

        ret = i915_gem_init_userptr(dev_priv);
        if (ret)
                return ret;

        /* This is just a security blanket to placate dragons.
         * On some systems, we very sporadically observe that the first TLBs
         * used by the CS may be stale, despite us poking the TLB reset. If
         * we hold the forcewake during initialisation these problems
         * just magically go away.
         */
        mutex_lock(&dev_priv->drm.struct_mutex);
        intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);

        ret = i915_gem_init_ggtt(dev_priv);
        if (ret)
                goto out_unlock;

        ret = i915_gem_contexts_init(dev_priv);
        if (ret)
                goto out_unlock;

        ret = intel_engines_init(dev_priv);
        if (ret)
                goto out_unlock;

        ret = i915_gem_init_hw(dev_priv);
        if (ret == -EIO) {
                /* Allow engine initialisation to fail by marking the GPU as
                 * wedged. But we only want to do this where the GPU is angry,
                 * for all other failure, such as an allocation failure, bail.
                 */
                if (!i915_terminally_wedged(&dev_priv->gpu_error)) {
                        DRM_ERROR("Failed to initialize GPU, declaring it wedged\n");
                        i915_gem_set_wedged(dev_priv);
                }
                ret = 0;
        }

out_unlock:
        intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
        mutex_unlock(&dev_priv->drm.struct_mutex);

        return ret;
}

void i915_gem_init_mmio(struct drm_i915_private *i915)
{
        i915_gem_sanitize(i915);
}

void
i915_gem_cleanup_engines(struct drm_i915_private *dev_priv)
{
        struct intel_engine_cs *engine;
        enum intel_engine_id id;

        for_each_engine(engine, dev_priv, id)
                dev_priv->gt.cleanup_engine(engine);
}

void
i915_gem_load_init_fences(struct drm_i915_private *dev_priv)
{
        int i;

        if (INTEL_INFO(dev_priv)->gen >= 7 && !IS_VALLEYVIEW(dev_priv) &&
            !IS_CHERRYVIEW(dev_priv))
                dev_priv->num_fence_regs = 32;
        else if (INTEL_INFO(dev_priv)->gen >= 4 ||
                 IS_I945G(dev_priv) || IS_I945GM(dev_priv) ||
                 IS_G33(dev_priv) || IS_PINEVIEW(dev_priv))
                dev_priv->num_fence_regs = 16;
        else
                dev_priv->num_fence_regs = 8;

        if (intel_vgpu_active(dev_priv))
                dev_priv->num_fence_regs =
                                I915_READ(vgtif_reg(avail_rs.fence_num));

        /* Initialize fence registers to zero */
        for (i = 0; i < dev_priv->num_fence_regs; i++) {
                struct drm_i915_fence_reg *fence = &dev_priv->fence_regs[i];

                fence->i915 = dev_priv;
                fence->id = i;
                list_add_tail(&fence->link, &dev_priv->mm.fence_list);
        }
        i915_gem_restore_fences(dev_priv);

        i915_gem_detect_bit_6_swizzle(dev_priv);
}

int
i915_gem_load_init(struct drm_i915_private *dev_priv)
{
        int err = -ENOMEM;

        dev_priv->objects = KMEM_CACHE(drm_i915_gem_object, SLAB_HWCACHE_ALIGN);
        if (!dev_priv->objects)
                goto err_out;

        dev_priv->vmas = KMEM_CACHE(i915_vma, SLAB_HWCACHE_ALIGN);
        if (!dev_priv->vmas)
                goto err_objects;

        dev_priv->luts = KMEM_CACHE(i915_lut_handle, 0);
        if (!dev_priv->luts)
                goto err_vmas;

        dev_priv->requests = KMEM_CACHE(drm_i915_gem_request,
                                        SLAB_HWCACHE_ALIGN |
                                        SLAB_RECLAIM_ACCOUNT |
                                        SLAB_TYPESAFE_BY_RCU);
        if (!dev_priv->requests)
                goto err_luts;

        dev_priv->dependencies = KMEM_CACHE(i915_dependency,
                                            SLAB_HWCACHE_ALIGN |
                                            SLAB_RECLAIM_ACCOUNT);
        if (!dev_priv->dependencies)
                goto err_requests;

        dev_priv->priorities = KMEM_CACHE(i915_priolist, SLAB_HWCACHE_ALIGN);
        if (!dev_priv->priorities)
                goto err_dependencies;

        mutex_lock(&dev_priv->drm.struct_mutex);
        INIT_LIST_HEAD(&dev_priv->gt.timelines);
        err = i915_gem_timeline_init__global(dev_priv);
        mutex_unlock(&dev_priv->drm.struct_mutex);
        if (err)
                goto err_priorities;

        INIT_WORK(&dev_priv->mm.free_work, __i915_gem_free_work);

        spin_lock_init(&dev_priv->mm.obj_lock);
        spin_lock_init(&dev_priv->mm.free_lock);
        init_llist_head(&dev_priv->mm.free_list);
        INIT_LIST_HEAD(&dev_priv->mm.unbound_list);
        INIT_LIST_HEAD(&dev_priv->mm.bound_list);
        INIT_LIST_HEAD(&dev_priv->mm.fence_list);
        INIT_LIST_HEAD(&dev_priv->mm.userfault_list);

        INIT_DELAYED_WORK(&dev_priv->gt.retire_work,
                          i915_gem_retire_work_handler);
        INIT_DELAYED_WORK(&dev_priv->gt.idle_work,
                          i915_gem_idle_work_handler);
        init_waitqueue_head(&dev_priv->gpu_error.wait_queue);
        init_waitqueue_head(&dev_priv->gpu_error.reset_queue);

        atomic_set(&dev_priv->mm.bsd_engine_dispatch_index, 0);

        spin_lock_init(&dev_priv->fb_tracking.lock);

        err = i915_gemfs_init(dev_priv);
        if (err)
                DRM_NOTE("Unable to create a private tmpfs mount, hugepage support will be disabled(%d).\n", err);

        return 0;

err_priorities:
        kmem_cache_destroy(dev_priv->priorities);
err_dependencies:
        kmem_cache_destroy(dev_priv->dependencies);
err_requests:
        kmem_cache_destroy(dev_priv->requests);
err_luts:
        kmem_cache_destroy(dev_priv->luts);
err_vmas:
        kmem_cache_destroy(dev_priv->vmas);
err_objects:
        kmem_cache_destroy(dev_priv->objects);
err_out:
        return err;
}

void i915_gem_load_cleanup(struct drm_i915_private *dev_priv)
{
        i915_gem_drain_freed_objects(dev_priv);
        WARN_ON(!llist_empty(&dev_priv->mm.free_list));
        WARN_ON(dev_priv->mm.object_count);

        mutex_lock(&dev_priv->drm.struct_mutex);
        i915_gem_timeline_fini(&dev_priv->gt.global_timeline);
        WARN_ON(!list_empty(&dev_priv->gt.timelines));
        mutex_unlock(&dev_priv->drm.struct_mutex);

        kmem_cache_destroy(dev_priv->priorities);
        kmem_cache_destroy(dev_priv->dependencies);
        kmem_cache_destroy(dev_priv->requests);
        kmem_cache_destroy(dev_priv->luts);
        kmem_cache_destroy(dev_priv->vmas);
        kmem_cache_destroy(dev_priv->objects);

        /* And ensure that our DESTROY_BY_RCU slabs are truly destroyed */
        rcu_barrier();

        i915_gemfs_fini(dev_priv);
}

int i915_gem_freeze(struct drm_i915_private *dev_priv)
{
        /* Discard all purgeable objects, let userspace recover those as
         * required after resuming.
         */
        i915_gem_shrink_all(dev_priv);

        return 0;
}

int i915_gem_freeze_late(struct drm_i915_private *dev_priv)
{
        struct drm_i915_gem_object *obj;
        struct list_head *phases[] = {
                &dev_priv->mm.unbound_list,
                &dev_priv->mm.bound_list,
                NULL
        }, **p;

        /* Called just before we write the hibernation image.
         *
         * We need to update the domain tracking to reflect that the CPU
         * will be accessing all the pages to create and restore from the
         * hibernation, and so upon restoration those pages will be in the
         * CPU domain.
         *
         * To make sure the hibernation image contains the latest state,
         * we update that state just before writing out the image.
         *
         * To try and reduce the hibernation image, we manually shrink
         * the objects as well, see i915_gem_freeze()
         */

        i915_gem_shrink(dev_priv, -1UL, NULL, I915_SHRINK_UNBOUND);
        i915_gem_drain_freed_objects(dev_priv);

        spin_lock(&dev_priv->mm.obj_lock);
        for (p = phases; *p; p++) {
                list_for_each_entry(obj, *p, mm.link)
                        __start_cpu_write(obj);
        }
        spin_unlock(&dev_priv->mm.obj_lock);

        return 0;
}

void i915_gem_release(struct drm_device *dev, struct drm_file *file)
{
        struct drm_i915_file_private *file_priv = file->driver_priv;
        struct drm_i915_gem_request *request;

        /* Clean up our request list when the client is going away, so that
         * later retire_requests won't dereference our soon-to-be-gone
         * file_priv.
         */
        spin_lock(&file_priv->mm.lock);
        list_for_each_entry(request, &file_priv->mm.request_list, client_link)
                request->file_priv = NULL;
        spin_unlock(&file_priv->mm.lock);
}

int i915_gem_open(struct drm_i915_private *i915, struct drm_file *file)
{
        struct drm_i915_file_private *file_priv;
        int ret;

        DRM_DEBUG("\n");

        file_priv = kzalloc(sizeof(*file_priv), GFP_KERNEL);
        if (!file_priv)
                return -ENOMEM;

        file->driver_priv = file_priv;
        file_priv->dev_priv = i915;
        file_priv->file = file;

        spin_lock_init(&file_priv->mm.lock);
        INIT_LIST_HEAD(&file_priv->mm.request_list);

        file_priv->bsd_engine = -1;

        ret = i915_gem_context_open(i915, file);
        if (ret)
                kfree(file_priv);

        return ret;
}

/**
 * i915_gem_track_fb - update frontbuffer tracking
 * @old: current GEM buffer for the frontbuffer slots
 * @new: new GEM buffer for the frontbuffer slots
 * @frontbuffer_bits: bitmask of frontbuffer slots
 *
 * This updates the frontbuffer tracking bits @frontbuffer_bits by clearing them
 * from @old and setting them in @new. Both @old and @new can be NULL.
 */
void i915_gem_track_fb(struct drm_i915_gem_object *old,
                       struct drm_i915_gem_object *new,
                       unsigned frontbuffer_bits)
{
        /* Control of individual bits within the mask are guarded by
         * the owning plane->mutex, i.e. we can never see concurrent
         * manipulation of individual bits. But since the bitfield as a whole
         * is updated using RMW, we need to use atomics in order to update
         * the bits.
         */
        BUILD_BUG_ON(INTEL_FRONTBUFFER_BITS_PER_PIPE * I915_MAX_PIPES >
                     sizeof(atomic_t) * BITS_PER_BYTE);

        if (old) {
                WARN_ON(!(atomic_read(&old->frontbuffer_bits) & frontbuffer_bits));
                atomic_andnot(frontbuffer_bits, &old->frontbuffer_bits);
        }

        if (new) {
                WARN_ON(atomic_read(&new->frontbuffer_bits) & frontbuffer_bits);
                atomic_or(frontbuffer_bits, &new->frontbuffer_bits);
        }
}

/* Allocate a new GEM object and fill it with the supplied data */
struct drm_i915_gem_object *
i915_gem_object_create_from_data(struct drm_i915_private *dev_priv,
                                 const void *data, size_t size)
{
        struct drm_i915_gem_object *obj;
        struct file *file;
        size_t offset;
        int err;

        obj = i915_gem_object_create(dev_priv, round_up(size, PAGE_SIZE));
        if (IS_ERR(obj))
                return obj;

        GEM_BUG_ON(obj->base.write_domain != I915_GEM_DOMAIN_CPU);

        file = obj->base.filp;
        offset = 0;
        do {
                unsigned int len = min_t(typeof(size), size, PAGE_SIZE);
                struct page *page;
                void *pgdata, *vaddr;

                err = pagecache_write_begin(file, file->f_mapping,
                                            offset, len, 0,
                                            &page, &pgdata);
                if (err < 0)
                        goto fail;

                vaddr = kmap(page);
                memcpy(vaddr, data, len);
                kunmap(page);

                err = pagecache_write_end(file, file->f_mapping,
                                          offset, len, len,
                                          page, pgdata);
                if (err < 0)
                        goto fail;

                size -= len;
                data += len;
                offset += len;
        } while (size);

        return obj;

fail:
        i915_gem_object_put(obj);
        return ERR_PTR(err);
}

struct scatterlist *
i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
                       unsigned int n,
                       unsigned int *offset)
{
        struct i915_gem_object_page_iter *iter = &obj->mm.get_page;
        struct scatterlist *sg;
        unsigned int idx, count;

        might_sleep();
        GEM_BUG_ON(n >= obj->base.size >> PAGE_SHIFT);
        GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));

        /* As we iterate forward through the sg, we record each entry in a
         * radixtree for quick repeated (backwards) lookups. If we have seen
         * this index previously, we will have an entry for it.
         *
         * Initial lookup is O(N), but this is amortized to O(1) for
         * sequential page access (where each new request is consecutive
         * to the previous one). Repeated lookups are O(lg(obj->base.size)),
         * i.e. O(1) with a large constant!
         */
        if (n < READ_ONCE(iter->sg_idx))
                goto lookup;

        mutex_lock(&iter->lock);

        /* We prefer to reuse the last sg so that repeated lookup of this
         * (or the subsequent) sg are fast - comparing against the last
         * sg is faster than going through the radixtree.
         */

        sg = iter->sg_pos;
        idx = iter->sg_idx;
        count = __sg_page_count(sg);

        while (idx + count <= n) {
                unsigned long exception, i;
                int ret;

                /* If we cannot allocate and insert this entry, or the
                 * individual pages from this range, cancel updating the
                 * sg_idx so that on this lookup we are forced to linearly
                 * scan onwards, but on future lookups we will try the
                 * insertion again (in which case we need to be careful of
                 * the error return reporting that we have already inserted
                 * this index).
                 */
                ret = radix_tree_insert(&iter->radix, idx, sg);
                if (ret && ret != -EEXIST)
                        goto scan;

                exception =
                        RADIX_TREE_EXCEPTIONAL_ENTRY |
                        idx << RADIX_TREE_EXCEPTIONAL_SHIFT;
                for (i = 1; i < count; i++) {
                        ret = radix_tree_insert(&iter->radix, idx + i,
                                                (void *)exception);
                        if (ret && ret != -EEXIST)
                                goto scan;
                }

                idx += count;
                sg = ____sg_next(sg);
                count = __sg_page_count(sg);
        }

scan:
        iter->sg_pos = sg;
        iter->sg_idx = idx;

        mutex_unlock(&iter->lock);

        if (unlikely(n < idx)) /* insertion completed by another thread */
                goto lookup;

        /* In case we failed to insert the entry into the radixtree, we need
         * to look beyond the current sg.
         */
        while (idx + count <= n) {
                idx += count;
                sg = ____sg_next(sg);
                count = __sg_page_count(sg);
        }

        *offset = n - idx;
        return sg;

lookup:
        rcu_read_lock();

        sg = radix_tree_lookup(&iter->radix, n);
        GEM_BUG_ON(!sg);

        /* If this index is in the middle of multi-page sg entry,
         * the radixtree will contain an exceptional entry that points
         * to the start of that range. We will return the pointer to
         * the base page and the offset of this page within the
         * sg entry's range.
         */
        *offset = 0;
        if (unlikely(radix_tree_exception(sg))) {
                unsigned long base =
                        (unsigned long)sg >> RADIX_TREE_EXCEPTIONAL_SHIFT;

                sg = radix_tree_lookup(&iter->radix, base);
                GEM_BUG_ON(!sg);

                *offset = n - base;
        }

        rcu_read_unlock();

        return sg;
}

struct page *
i915_gem_object_get_page(struct drm_i915_gem_object *obj, unsigned int n)
{
        struct scatterlist *sg;
        unsigned int offset;

        GEM_BUG_ON(!i915_gem_object_has_struct_page(obj));

        sg = i915_gem_object_get_sg(obj, n, &offset);
        return nth_page(sg_page(sg), offset);
}

/* Like i915_gem_object_get_page(), but mark the returned page dirty */
struct page *
i915_gem_object_get_dirty_page(struct drm_i915_gem_object *obj,
                               unsigned int n)
{
        struct page *page;

        page = i915_gem_object_get_page(obj, n);
        if (!obj->mm.dirty)
                set_page_dirty(page);

        return page;
}

dma_addr_t
i915_gem_object_get_dma_address(struct drm_i915_gem_object *obj,
                                unsigned long n)
{
        struct scatterlist *sg;
        unsigned int offset;

        sg = i915_gem_object_get_sg(obj, n, &offset);
        return sg_dma_address(sg) + (offset << PAGE_SHIFT);
}

int i915_gem_object_attach_phys(struct drm_i915_gem_object *obj, int align)
{
        struct sg_table *pages;
        int err;

        if (align > obj->base.size)
                return -EINVAL;

        if (obj->ops == &i915_gem_phys_ops)
                return 0;

        if (obj->ops != &i915_gem_object_ops)
                return -EINVAL;

        err = i915_gem_object_unbind(obj);
        if (err)
                return err;

        mutex_lock(&obj->mm.lock);

        if (obj->mm.madv != I915_MADV_WILLNEED) {
                err = -EFAULT;
                goto err_unlock;
        }

        if (obj->mm.quirked) {
                err = -EFAULT;
                goto err_unlock;
        }

        if (obj->mm.mapping) {
                err = -EBUSY;
                goto err_unlock;
        }

        pages = fetch_and_zero(&obj->mm.pages);
        if (pages) {
                struct drm_i915_private *i915 = to_i915(obj->base.dev);

                __i915_gem_object_reset_page_iter(obj);

                spin_lock(&i915->mm.obj_lock);
                list_del(&obj->mm.link);
                spin_unlock(&i915->mm.obj_lock);
        }

        obj->ops = &i915_gem_phys_ops;

        err = ____i915_gem_object_get_pages(obj);
        if (err)
                goto err_xfer;

        /* Perma-pin (until release) the physical set of pages */
        __i915_gem_object_pin_pages(obj);

        if (!IS_ERR_OR_NULL(pages))
                i915_gem_object_ops.put_pages(obj, pages);
        mutex_unlock(&obj->mm.lock);
        return 0;

err_xfer:
        obj->ops = &i915_gem_object_ops;
        obj->mm.pages = pages;
err_unlock:
        mutex_unlock(&obj->mm.lock);
        return err;
}

#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftests/scatterlist.c"
#include "selftests/mock_gem_device.c"
#include "selftests/huge_gem_object.c"
#include "selftests/huge_pages.c"
#include "selftests/i915_gem_object.c"
#include "selftests/i915_gem_coherency.c"
#endif