OSCL-LXR linux-6.0.1/​drivers/​gpu/​drm/​i915/​gem/​i915_gem_ttm.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: MIT
 /*
  * Copyright © 2021 Intel Corporation
  */
 
 #include <linux/shmem_fs.h>
 
 #include <drm/ttm/ttm_bo_driver.h>
 #include <drm/ttm/ttm_placement.h>
 #include <drm/drm_buddy.h>
 
 #include "i915_drv.h"
 #include "i915_ttm_buddy_manager.h"
 #include "intel_memory_region.h"
 #include "intel_region_ttm.h"
 
 #include "gem/i915_gem_mman.h"
 #include "gem/i915_gem_object.h"
 #include "gem/i915_gem_region.h"
 #include "gem/i915_gem_ttm.h"
 #include "gem/i915_gem_ttm_move.h"
 #include "gem/i915_gem_ttm_pm.h"
 #include "gt/intel_gpu_commands.h"
 
 #define I915_TTM_PRIO_PURGE     0
 #define I915_TTM_PRIO_NO_PAGES  1
 #define I915_TTM_PRIO_HAS_PAGES 2
 #define I915_TTM_PRIO_NEEDS_CPU_ACCESS 3
 
 /*
  * Size of struct ttm_place vector in on-stack struct ttm_placement allocs
  */
 #define I915_TTM_MAX_PLACEMENTS INTEL_REGION_UNKNOWN
 
 /**
  * struct i915_ttm_tt - TTM page vector with additional private information
  * @ttm: The base TTM page vector.
  * @dev: The struct device used for dma mapping and unmapping.
  * @cached_rsgt: The cached scatter-gather table.
  * @is_shmem: Set if using shmem.
  * @filp: The shmem file, if using shmem backend.
  *
  * Note that DMA may be going on right up to the point where the page-
  * vector is unpopulated in delayed destroy. Hence keep the
  * scatter-gather table mapped and cached up to that point. This is
  * different from the cached gem object io scatter-gather table which
  * doesn't have an associated dma mapping.
  */
 struct i915_ttm_tt {
     struct ttm_tt ttm;
     struct device *dev;
     struct i915_refct_sgt cached_rsgt;
 
     bool is_shmem;
     struct file *filp;
 };
 
 static const struct ttm_place sys_placement_flags = {
     .fpfn = 0,
     .lpfn = 0,
     .mem_type = I915_PL_SYSTEM,
     .flags = 0,
 };
 
 static struct ttm_placement i915_sys_placement = {
     .num_placement = 1,
     .placement = &sys_placement_flags,
     .num_busy_placement = 1,
     .busy_placement = &sys_placement_flags,
 };
 
 /**
  * i915_ttm_sys_placement - Return the struct ttm_placement to be
  * used for an object in system memory.
  *
  * Rather than making the struct extern, use this
  * function.
  *
  * Return: A pointer to a static variable for sys placement.
  */
 struct ttm_placement *i915_ttm_sys_placement(void)
 {
     return &i915_sys_placement;
 }
 
 static int i915_ttm_err_to_gem(int err)
 {
     /* Fastpath */
     if (likely(!err))
         return 0;
 
     switch (err) {
     case -EBUSY:
         /*
          * TTM likes to convert -EDEADLK to -EBUSY, and wants us to
          * restart the operation, since we don't record the contending
          * lock. We use -EAGAIN to restart.
          */
         return -EAGAIN;
     case -ENOSPC:
         /*
          * Memory type / region is full, and we can't evict.
          * Except possibly system, that returns -ENOMEM;
          */
         return -ENXIO;
     default:
         break;
     }
 
     return err;
 }
 
 static enum ttm_caching
 i915_ttm_select_tt_caching(const struct drm_i915_gem_object *obj)
 {
     /*
      * Objects only allowed in system get cached cpu-mappings, or when
      * evicting lmem-only buffers to system for swapping. Other objects get
      * WC mapping for now. Even if in system.
      */
     if (obj->mm.n_placements <= 1)
         return ttm_cached;
 
     return ttm_write_combined;
 }
 
 static void
 i915_ttm_place_from_region(const struct intel_memory_region *mr,
                struct ttm_place *place,
                resource_size_t offset,
                resource_size_t size,
                unsigned int flags)
 {
     memset(place, 0, sizeof(*place));
     place->mem_type = intel_region_to_ttm_type(mr);
 
     if (mr->type == INTEL_MEMORY_SYSTEM)
         return;
 
     if (flags & I915_BO_ALLOC_CONTIGUOUS)
         place->flags |= TTM_PL_FLAG_CONTIGUOUS;
     if (offset != I915_BO_INVALID_OFFSET) {
         place->fpfn = offset >> PAGE_SHIFT;
         place->lpfn = place->fpfn + (size >> PAGE_SHIFT);
     } else if (mr->io_size && mr->io_size < mr->total) {
         if (flags & I915_BO_ALLOC_GPU_ONLY) {
             place->flags |= TTM_PL_FLAG_TOPDOWN;
         } else {
             place->fpfn = 0;
             place->lpfn = mr->io_size >> PAGE_SHIFT;
         }
     }
 }
 
 static void
 i915_ttm_placement_from_obj(const struct drm_i915_gem_object *obj,
                 struct ttm_place *requested,
                 struct ttm_place *busy,
                 struct ttm_placement *placement)
 {
     unsigned int num_allowed = obj->mm.n_placements;
     unsigned int flags = obj->flags;
     unsigned int i;
 
     placement->num_placement = 1;
     i915_ttm_place_from_region(num_allowed ? obj->mm.placements[0] :
                    obj->mm.region, requested, obj->bo_offset,
                    obj->base.size, flags);
 
     /* Cache this on object? */
     placement->num_busy_placement = num_allowed;
     for (i = 0; i < placement->num_busy_placement; ++i)
         i915_ttm_place_from_region(obj->mm.placements[i], busy + i,
                        obj->bo_offset, obj->base.size, flags);
 
     if (num_allowed == 0) {
         *busy = *requested;
         placement->num_busy_placement = 1;
     }
 
     placement->placement = requested;
     placement->busy_placement = busy;
 }
 
 static int i915_ttm_tt_shmem_populate(struct ttm_device *bdev,
                       struct ttm_tt *ttm,
                       struct ttm_operation_ctx *ctx)
 {
     struct drm_i915_private *i915 = container_of(bdev, typeof(*i915), bdev);
     struct intel_memory_region *mr = i915->mm.regions[INTEL_MEMORY_SYSTEM];
     struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
     const unsigned int max_segment = i915_sg_segment_size();
     const size_t size = (size_t)ttm->num_pages << PAGE_SHIFT;
     struct file *filp = i915_tt->filp;
     struct sgt_iter sgt_iter;
     struct sg_table *st;
     struct page *page;
     unsigned long i;
     int err;
 
     if (!filp) {
         struct address_space *mapping;
         gfp_t mask;
 
         filp = shmem_file_setup("i915-shmem-tt", size, VM_NORESERVE);
         if (IS_ERR(filp))
             return PTR_ERR(filp);
 
         mask = GFP_HIGHUSER | __GFP_RECLAIMABLE;
 
         mapping = filp->f_mapping;
         mapping_set_gfp_mask(mapping, mask);
         GEM_BUG_ON(!(mapping_gfp_mask(mapping) & __GFP_RECLAIM));
 
         i915_tt->filp = filp;
     }
 
     st = &i915_tt->cached_rsgt.table;
     err = shmem_sg_alloc_table(i915, st, size, mr, filp->f_mapping,
                    max_segment);
     if (err)
         return err;
 
     err = dma_map_sgtable(i915_tt->dev, st, DMA_BIDIRECTIONAL,
                   DMA_ATTR_SKIP_CPU_SYNC);
     if (err)
         goto err_free_st;
 
     i = 0;
     for_each_sgt_page(page, sgt_iter, st)
         ttm->pages[i++] = page;
 
     if (ttm->page_flags & TTM_TT_FLAG_SWAPPED)
         ttm->page_flags &= ~TTM_TT_FLAG_SWAPPED;
 
     return 0;
 
 err_free_st:
     shmem_sg_free_table(st, filp->f_mapping, false, false);
 
     return err;
 }
 
 static void i915_ttm_tt_shmem_unpopulate(struct ttm_tt *ttm)
 {
     struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
     bool backup = ttm->page_flags & TTM_TT_FLAG_SWAPPED;
     struct sg_table *st = &i915_tt->cached_rsgt.table;
 
     shmem_sg_free_table(st, file_inode(i915_tt->filp)->i_mapping,
                 backup, backup);
 }
 
 static void i915_ttm_tt_release(struct kref *ref)
 {
     struct i915_ttm_tt *i915_tt =
         container_of(ref, typeof(*i915_tt), cached_rsgt.kref);
     struct sg_table *st = &i915_tt->cached_rsgt.table;
 
     GEM_WARN_ON(st->sgl);
 
     kfree(i915_tt);
 }
 
 static const struct i915_refct_sgt_ops tt_rsgt_ops = {
     .release = i915_ttm_tt_release
 };
 
 static struct ttm_tt *i915_ttm_tt_create(struct ttm_buffer_object *bo,
                      uint32_t page_flags)
 {
     struct drm_i915_private *i915 = container_of(bo->bdev, typeof(*i915),
                              bdev);
     struct ttm_resource_manager *man =
         ttm_manager_type(bo->bdev, bo->resource->mem_type);
     struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
     unsigned long ccs_pages = 0;
     enum ttm_caching caching;
     struct i915_ttm_tt *i915_tt;
     int ret;
 
     if (!obj)
         return NULL;
 
     i915_tt = kzalloc(sizeof(*i915_tt), GFP_KERNEL);
     if (!i915_tt)
         return NULL;
 
     if (obj->flags & I915_BO_ALLOC_CPU_CLEAR &&
         man->use_tt)
         page_flags |= TTM_TT_FLAG_ZERO_ALLOC;
 
     caching = i915_ttm_select_tt_caching(obj);
     if (i915_gem_object_is_shrinkable(obj) && caching == ttm_cached) {
         page_flags |= TTM_TT_FLAG_EXTERNAL |
                   TTM_TT_FLAG_EXTERNAL_MAPPABLE;
         i915_tt->is_shmem = true;
     }
 
     if (i915_gem_object_needs_ccs_pages(obj))
         ccs_pages = DIV_ROUND_UP(DIV_ROUND_UP(bo->base.size,
                               NUM_BYTES_PER_CCS_BYTE),
                      PAGE_SIZE);
 
     ret = ttm_tt_init(&i915_tt->ttm, bo, page_flags, caching, ccs_pages);
     if (ret)
         goto err_free;
 
     __i915_refct_sgt_init(&i915_tt->cached_rsgt, bo->base.size,
                   &tt_rsgt_ops);
 
     i915_tt->dev = obj->base.dev->dev;
 
     return &i915_tt->ttm;
 
 err_free:
     kfree(i915_tt);
     return NULL;
 }
 
 static int i915_ttm_tt_populate(struct ttm_device *bdev,
                 struct ttm_tt *ttm,
                 struct ttm_operation_ctx *ctx)
 {
     struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
 
     if (i915_tt->is_shmem)
         return i915_ttm_tt_shmem_populate(bdev, ttm, ctx);
 
     return ttm_pool_alloc(&bdev->pool, ttm, ctx);
 }
 
 static void i915_ttm_tt_unpopulate(struct ttm_device *bdev, struct ttm_tt *ttm)
 {
     struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
     struct sg_table *st = &i915_tt->cached_rsgt.table;
 
     if (st->sgl)
         dma_unmap_sgtable(i915_tt->dev, st, DMA_BIDIRECTIONAL, 0);
 
     if (i915_tt->is_shmem) {
         i915_ttm_tt_shmem_unpopulate(ttm);
     } else {
         sg_free_table(st);
         ttm_pool_free(&bdev->pool, ttm);
     }
 }
 
 static void i915_ttm_tt_destroy(struct ttm_device *bdev, struct ttm_tt *ttm)
 {
     struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
 
     if (i915_tt->filp)
         fput(i915_tt->filp);
 
     ttm_tt_fini(ttm);
     i915_refct_sgt_put(&i915_tt->cached_rsgt);
 }
 
 static bool i915_ttm_eviction_valuable(struct ttm_buffer_object *bo,
                        const struct ttm_place *place)
 {
     struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
     struct ttm_resource *res = bo->resource;
 
     if (!obj)
         return false;
 
     /*
      * EXTERNAL objects should never be swapped out by TTM, instead we need
      * to handle that ourselves. TTM will already skip such objects for us,
      * but we would like to avoid grabbing locks for no good reason.
      */
     if (bo->ttm && bo->ttm->page_flags & TTM_TT_FLAG_EXTERNAL)
         return false;
 
     /* Will do for now. Our pinned objects are still on TTM's LRU lists */
     if (!i915_gem_object_evictable(obj))
         return false;
 
     switch (res->mem_type) {
     case I915_PL_LMEM0: {
         struct ttm_resource_manager *man =
             ttm_manager_type(bo->bdev, res->mem_type);
         struct i915_ttm_buddy_resource *bman_res =
             to_ttm_buddy_resource(res);
         struct drm_buddy *mm = bman_res->mm;
         struct drm_buddy_block *block;
 
         if (!place->fpfn && !place->lpfn)
             return true;
 
         GEM_BUG_ON(!place->lpfn);
 
         /*
          * If we just want something mappable then we can quickly check
          * if the current victim resource is using any of the CPU
          * visible portion.
          */
         if (!place->fpfn &&
             place->lpfn == i915_ttm_buddy_man_visible_size(man))
             return bman_res->used_visible_size > 0;
 
         /* Real range allocation */
         list_for_each_entry(block, &bman_res->blocks, link) {
             unsigned long fpfn =
                 drm_buddy_block_offset(block) >> PAGE_SHIFT;
             unsigned long lpfn = fpfn +
                 (drm_buddy_block_size(mm, block) >> PAGE_SHIFT);
 
             if (place->fpfn < lpfn && place->lpfn > fpfn)
                 return true;
         }
         return false;
     } default:
         break;
     }
 
     return true;
 }
 
 static void i915_ttm_evict_flags(struct ttm_buffer_object *bo,
                  struct ttm_placement *placement)
 {
     *placement = i915_sys_placement;
 }
 
 /**
  * i915_ttm_free_cached_io_rsgt - Free object cached LMEM information
  * @obj: The GEM object
  * This function frees any LMEM-related information that is cached on
  * the object. For example the radix tree for fast page lookup and the
  * cached refcounted sg-table
  */
 void i915_ttm_free_cached_io_rsgt(struct drm_i915_gem_object *obj)
 {
     struct radix_tree_iter iter;
     void __rcu **slot;
 
     if (!obj->ttm.cached_io_rsgt)
         return;
 
     rcu_read_lock();
     radix_tree_for_each_slot(slot, &obj->ttm.get_io_page.radix, &iter, 0)
         radix_tree_delete(&obj->ttm.get_io_page.radix, iter.index);
     rcu_read_unlock();
 
     i915_refct_sgt_put(obj->ttm.cached_io_rsgt);
     obj->ttm.cached_io_rsgt = NULL;
 }
 
 /**
  * i915_ttm_purge - Clear an object of its memory
  * @obj: The object
  *
  * This function is called to clear an object of it's memory when it is
  * marked as not needed anymore.
  *
  * Return: 0 on success, negative error code on failure.
  */
 int i915_ttm_purge(struct drm_i915_gem_object *obj)
 {
     struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
     struct i915_ttm_tt *i915_tt =
         container_of(bo->ttm, typeof(*i915_tt), ttm);
     struct ttm_operation_ctx ctx = {
         .interruptible = true,
         .no_wait_gpu = false,
     };
     struct ttm_placement place = {};
     int ret;
 
     if (obj->mm.madv == __I915_MADV_PURGED)
         return 0;
 
     ret = ttm_bo_validate(bo, &place, &ctx);
     if (ret)
         return ret;
 
     if (bo->ttm && i915_tt->filp) {
         /*
          * The below fput(which eventually calls shmem_truncate) might
          * be delayed by worker, so when directly called to purge the
          * pages(like by the shrinker) we should try to be more
          * aggressive and release the pages immediately.
          */
         shmem_truncate_range(file_inode(i915_tt->filp),
                      0, (loff_t)-1);
         fput(fetch_and_zero(&i915_tt->filp));
     }
 
     obj->write_domain = 0;
     obj->read_domains = 0;
     i915_ttm_adjust_gem_after_move(obj);
     i915_ttm_free_cached_io_rsgt(obj);
     obj->mm.madv = __I915_MADV_PURGED;
 
     return 0;
 }
 
 static int i915_ttm_shrink(struct drm_i915_gem_object *obj, unsigned int flags)
 {
     struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
     struct i915_ttm_tt *i915_tt =
         container_of(bo->ttm, typeof(*i915_tt), ttm);
     struct ttm_operation_ctx ctx = {
         .interruptible = true,
         .no_wait_gpu = flags & I915_GEM_OBJECT_SHRINK_NO_GPU_WAIT,
     };
     struct ttm_placement place = {};
     int ret;
 
     if (!bo->ttm || bo->resource->mem_type != TTM_PL_SYSTEM)
         return 0;
 
     GEM_BUG_ON(!i915_tt->is_shmem);
 
     if (!i915_tt->filp)
         return 0;
 
     ret = ttm_bo_wait_ctx(bo, &ctx);
     if (ret)
         return ret;
 
     switch (obj->mm.madv) {
     case I915_MADV_DONTNEED:
         return i915_ttm_purge(obj);
     case __I915_MADV_PURGED:
         return 0;
     }
 
     if (bo->ttm->page_flags & TTM_TT_FLAG_SWAPPED)
         return 0;
 
     bo->ttm->page_flags |= TTM_TT_FLAG_SWAPPED;
     ret = ttm_bo_validate(bo, &place, &ctx);
     if (ret) {
         bo->ttm->page_flags &= ~TTM_TT_FLAG_SWAPPED;
         return ret;
     }
 
     if (flags & I915_GEM_OBJECT_SHRINK_WRITEBACK)
         __shmem_writeback(obj->base.size, i915_tt->filp->f_mapping);
 
     return 0;
 }
 
 static void i915_ttm_delete_mem_notify(struct ttm_buffer_object *bo)
 {
     struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
 
     if (likely(obj)) {
         __i915_gem_object_pages_fini(obj);
         i915_ttm_free_cached_io_rsgt(obj);
     }
 }
 
 static struct i915_refct_sgt *i915_ttm_tt_get_st(struct ttm_tt *ttm)
 {
     struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
     struct sg_table *st;
     int ret;
 
     if (i915_tt->cached_rsgt.table.sgl)
         return i915_refct_sgt_get(&i915_tt->cached_rsgt);
 
     st = &i915_tt->cached_rsgt.table;
     ret = sg_alloc_table_from_pages_segment(st,
             ttm->pages, ttm->num_pages,
             0, (unsigned long)ttm->num_pages << PAGE_SHIFT,
             i915_sg_segment_size(), GFP_KERNEL);
     if (ret) {
         st->sgl = NULL;
         return ERR_PTR(ret);
     }
 
     ret = dma_map_sgtable(i915_tt->dev, st, DMA_BIDIRECTIONAL, 0);
     if (ret) {
         sg_free_table(st);
         return ERR_PTR(ret);
     }
 
     return i915_refct_sgt_get(&i915_tt->cached_rsgt);
 }
 
 /**
  * i915_ttm_resource_get_st - Get a refcounted sg-table pointing to the
  * resource memory
  * @obj: The GEM object used for sg-table caching
  * @res: The struct ttm_resource for which an sg-table is requested.
  *
  * This function returns a refcounted sg-table representing the memory
  * pointed to by @res. If @res is the object's current resource it may also
  * cache the sg_table on the object or attempt to access an already cached
  * sg-table. The refcounted sg-table needs to be put when no-longer in use.
  *
  * Return: A valid pointer to a struct i915_refct_sgt or error pointer on
  * failure.
  */
 struct i915_refct_sgt *
 i915_ttm_resource_get_st(struct drm_i915_gem_object *obj,
              struct ttm_resource *res)
 {
     struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
     u32 page_alignment;
 
     if (!i915_ttm_gtt_binds_lmem(res))
         return i915_ttm_tt_get_st(bo->ttm);
 
     page_alignment = bo->page_alignment << PAGE_SHIFT;
     if (!page_alignment)
         page_alignment = obj->mm.region->min_page_size;
 
     /*
      * If CPU mapping differs, we need to add the ttm_tt pages to
      * the resulting st. Might make sense for GGTT.
      */
     GEM_WARN_ON(!i915_ttm_cpu_maps_iomem(res));
     if (bo->resource == res) {
         if (!obj->ttm.cached_io_rsgt) {
             struct i915_refct_sgt *rsgt;
 
             rsgt = intel_region_ttm_resource_to_rsgt(obj->mm.region,
                                  res,
                                  page_alignment);
             if (IS_ERR(rsgt))
                 return rsgt;
 
             obj->ttm.cached_io_rsgt = rsgt;
         }
         return i915_refct_sgt_get(obj->ttm.cached_io_rsgt);
     }
 
     return intel_region_ttm_resource_to_rsgt(obj->mm.region, res,
                          page_alignment);
 }
 
 static int i915_ttm_truncate(struct drm_i915_gem_object *obj)
 {
     struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
     int err;
 
     WARN_ON_ONCE(obj->mm.madv == I915_MADV_WILLNEED);
 
     err = i915_ttm_move_notify(bo);
     if (err)
         return err;
 
     return i915_ttm_purge(obj);
 }
 
 static void i915_ttm_swap_notify(struct ttm_buffer_object *bo)
 {
     struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
     int ret;
 
     if (!obj)
         return;
 
     ret = i915_ttm_move_notify(bo);
     GEM_WARN_ON(ret);
     GEM_WARN_ON(obj->ttm.cached_io_rsgt);
     if (!ret && obj->mm.madv != I915_MADV_WILLNEED)
         i915_ttm_purge(obj);
 }
 
 /**
  * i915_ttm_resource_mappable - Return true if the ttm resource is CPU
  * accessible.
  * @res: The TTM resource to check.
  *
  * This is interesting on small-BAR systems where we may encounter lmem objects
  * that can't be accessed via the CPU.
  */
 bool i915_ttm_resource_mappable(struct ttm_resource *res)
 {
     struct i915_ttm_buddy_resource *bman_res = to_ttm_buddy_resource(res);
 
     if (!i915_ttm_cpu_maps_iomem(res))
         return true;
 
     return bman_res->used_visible_size == bman_res->base.num_pages;
 }
 
 static int i915_ttm_io_mem_reserve(struct ttm_device *bdev, struct ttm_resource *mem)
 {
     struct drm_i915_gem_object *obj = i915_ttm_to_gem(mem->bo);
     bool unknown_state;
 
     if (!obj)
         return -EINVAL;
 
     if (!kref_get_unless_zero(&obj->base.refcount))
         return -EINVAL;
 
     assert_object_held(obj);
 
     unknown_state = i915_gem_object_has_unknown_state(obj);
     i915_gem_object_put(obj);
     if (unknown_state)
         return -EINVAL;
 
     if (!i915_ttm_cpu_maps_iomem(mem))
         return 0;
 
     if (!i915_ttm_resource_mappable(mem))
         return -EINVAL;
 
     mem->bus.caching = ttm_write_combined;
     mem->bus.is_iomem = true;
 
     return 0;
 }
 
 static unsigned long i915_ttm_io_mem_pfn(struct ttm_buffer_object *bo,
                      unsigned long page_offset)
 {
     struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
     struct scatterlist *sg;
     unsigned long base;
     unsigned int ofs;
 
     GEM_BUG_ON(!obj);
     GEM_WARN_ON(bo->ttm);
 
     base = obj->mm.region->iomap.base - obj->mm.region->region.start;
     sg = __i915_gem_object_get_sg(obj, &obj->ttm.get_io_page, page_offset, &ofs, true);
 
     return ((base + sg_dma_address(sg)) >> PAGE_SHIFT) + ofs;
 }
 
 /*
  * All callbacks need to take care not to downcast a struct ttm_buffer_object
  * without checking its subclass, since it might be a TTM ghost object.
  */
 static struct ttm_device_funcs i915_ttm_bo_driver = {
     .ttm_tt_create = i915_ttm_tt_create,
     .ttm_tt_populate = i915_ttm_tt_populate,
     .ttm_tt_unpopulate = i915_ttm_tt_unpopulate,
     .ttm_tt_destroy = i915_ttm_tt_destroy,
     .eviction_valuable = i915_ttm_eviction_valuable,
     .evict_flags = i915_ttm_evict_flags,
     .move = i915_ttm_move,
     .swap_notify = i915_ttm_swap_notify,
     .delete_mem_notify = i915_ttm_delete_mem_notify,
     .io_mem_reserve = i915_ttm_io_mem_reserve,
     .io_mem_pfn = i915_ttm_io_mem_pfn,
 };
 
 /**
  * i915_ttm_driver - Return a pointer to the TTM device funcs
  *
  * Return: Pointer to statically allocated TTM device funcs.
  */
 struct ttm_device_funcs *i915_ttm_driver(void)
 {
     return &i915_ttm_bo_driver;
 }
 
 static int __i915_ttm_get_pages(struct drm_i915_gem_object *obj,
                 struct ttm_placement *placement)
 {
     struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
     struct ttm_operation_ctx ctx = {
         .interruptible = true,
         .no_wait_gpu = false,
     };
     int real_num_busy;
     int ret;
 
     /* First try only the requested placement. No eviction. */
     real_num_busy = fetch_and_zero(&placement->num_busy_placement);
     ret = ttm_bo_validate(bo, placement, &ctx);
     if (ret) {
         ret = i915_ttm_err_to_gem(ret);
         /*
          * Anything that wants to restart the operation gets to
          * do that.
          */
         if (ret == -EDEADLK || ret == -EINTR || ret == -ERESTARTSYS ||
             ret == -EAGAIN)
             return ret;
 
         /*
          * If the initial attempt fails, allow all accepted placements,
          * evicting if necessary.
          */
         placement->num_busy_placement = real_num_busy;
         ret = ttm_bo_validate(bo, placement, &ctx);
         if (ret)
             return i915_ttm_err_to_gem(ret);
     }
 
     if (bo->ttm && !ttm_tt_is_populated(bo->ttm)) {
         ret = ttm_tt_populate(bo->bdev, bo->ttm, &ctx);
         if (ret)
             return ret;
 
         i915_ttm_adjust_domains_after_move(obj);
         i915_ttm_adjust_gem_after_move(obj);
     }
 
     if (!i915_gem_object_has_pages(obj)) {
         struct i915_refct_sgt *rsgt =
             i915_ttm_resource_get_st(obj, bo->resource);
 
         if (IS_ERR(rsgt))
             return PTR_ERR(rsgt);
 
         GEM_BUG_ON(obj->mm.rsgt);
         obj->mm.rsgt = rsgt;
         __i915_gem_object_set_pages(obj, &rsgt->table,
                         i915_sg_dma_sizes(rsgt->table.sgl));
     }
 
     GEM_BUG_ON(bo->ttm && ((obj->base.size >> PAGE_SHIFT) < bo->ttm->num_pages));
     i915_ttm_adjust_lru(obj);
     return ret;
 }
 
 static int i915_ttm_get_pages(struct drm_i915_gem_object *obj)
 {
     struct ttm_place requested, busy[I915_TTM_MAX_PLACEMENTS];
     struct ttm_placement placement;
 
     GEM_BUG_ON(obj->mm.n_placements > I915_TTM_MAX_PLACEMENTS);
 
     /* Move to the requested placement. */
     i915_ttm_placement_from_obj(obj, &requested, busy, &placement);
 
     return __i915_ttm_get_pages(obj, &placement);
 }
 
 /**
  * DOC: Migration vs eviction
  *
  * GEM migration may not be the same as TTM migration / eviction. If
  * the TTM core decides to evict an object it may be evicted to a
  * TTM memory type that is not in the object's allowable GEM regions, or
  * in fact theoretically to a TTM memory type that doesn't correspond to
  * a GEM memory region. In that case the object's GEM region is not
  * updated, and the data is migrated back to the GEM region at
  * get_pages time. TTM may however set up CPU ptes to the object even
  * when it is evicted.
  * Gem forced migration using the i915_ttm_migrate() op, is allowed even
  * to regions that are not in the object's list of allowable placements.
  */
 static int __i915_ttm_migrate(struct drm_i915_gem_object *obj,
                   struct intel_memory_region *mr,
                   unsigned int flags)
 {
     struct ttm_place requested;
     struct ttm_placement placement;
     int ret;
 
     i915_ttm_place_from_region(mr, &requested, obj->bo_offset,
                    obj->base.size, flags);
     placement.num_placement = 1;
     placement.num_busy_placement = 1;
     placement.placement = &requested;
     placement.busy_placement = &requested;
 
     ret = __i915_ttm_get_pages(obj, &placement);
     if (ret)
         return ret;
 
     /*
      * Reinitialize the region bindings. This is primarily
      * required for objects where the new region is not in
      * its allowable placements.
      */
     if (obj->mm.region != mr) {
         i915_gem_object_release_memory_region(obj);
         i915_gem_object_init_memory_region(obj, mr);
     }
 
     return 0;
 }
 
 static int i915_ttm_migrate(struct drm_i915_gem_object *obj,
                 struct intel_memory_region *mr)
 {
     return __i915_ttm_migrate(obj, mr, obj->flags);
 }
 
 static void i915_ttm_put_pages(struct drm_i915_gem_object *obj,
                    struct sg_table *st)
 {
     /*
      * We're currently not called from a shrinker, so put_pages()
      * typically means the object is about to destroyed, or called
      * from move_notify(). So just avoid doing much for now.
      * If the object is not destroyed next, The TTM eviction logic
      * and shrinkers will move it out if needed.
      */
 
     if (obj->mm.rsgt)
         i915_refct_sgt_put(fetch_and_zero(&obj->mm.rsgt));
 }
 
 /**
  * i915_ttm_adjust_lru - Adjust an object's position on relevant LRU lists.
  * @obj: The object
  */
 void i915_ttm_adjust_lru(struct drm_i915_gem_object *obj)
 {
     struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
     struct i915_ttm_tt *i915_tt =
         container_of(bo->ttm, typeof(*i915_tt), ttm);
     bool shrinkable =
         bo->ttm && i915_tt->filp && ttm_tt_is_populated(bo->ttm);
 
     /*
      * Don't manipulate the TTM LRUs while in TTM bo destruction.
      * We're called through i915_ttm_delete_mem_notify().
      */
     if (!kref_read(&bo->kref))
         return;
 
     /*
      * We skip managing the shrinker LRU in set_pages() and just manage
      * everything here. This does at least solve the issue with having
      * temporary shmem mappings(like with evicted lmem) not being visible to
      * the shrinker. Only our shmem objects are shrinkable, everything else
      * we keep as unshrinkable.
      *
      * To make sure everything plays nice we keep an extra shrink pin in TTM
      * if the underlying pages are not currently shrinkable. Once we release
      * our pin, like when the pages are moved to shmem, the pages will then
      * be added to the shrinker LRU, assuming the caller isn't also holding
      * a pin.
      *
      * TODO: consider maybe also bumping the shrinker list here when we have
      * already unpinned it, which should give us something more like an LRU.
      *
      * TODO: There is a small window of opportunity for this function to
      * get called from eviction after we've dropped the last GEM refcount,
      * but before the TTM deleted flag is set on the object. Avoid
      * adjusting the shrinker list in such cases, since the object is
      * not available to the shrinker anyway due to its zero refcount.
      * To fix this properly we should move to a TTM shrinker LRU list for
      * these objects.
      */
     if (kref_get_unless_zero(&obj->base.refcount)) {
         if (shrinkable != obj->mm.ttm_shrinkable) {
             if (shrinkable) {
                 if (obj->mm.madv == I915_MADV_WILLNEED)
                     __i915_gem_object_make_shrinkable(obj);
                 else
                     __i915_gem_object_make_purgeable(obj);
             } else {
                 i915_gem_object_make_unshrinkable(obj);
             }
 
             obj->mm.ttm_shrinkable = shrinkable;
         }
         i915_gem_object_put(obj);
     }
 
     /*
      * Put on the correct LRU list depending on the MADV status
      */
     spin_lock(&bo->bdev->lru_lock);
     if (shrinkable) {
         /* Try to keep shmem_tt from being considered for shrinking. */
         bo->priority = TTM_MAX_BO_PRIORITY - 1;
     } else if (obj->mm.madv != I915_MADV_WILLNEED) {
         bo->priority = I915_TTM_PRIO_PURGE;
     } else if (!i915_gem_object_has_pages(obj)) {
         bo->priority = I915_TTM_PRIO_NO_PAGES;
     } else {
         struct ttm_resource_manager *man =
             ttm_manager_type(bo->bdev, bo->resource->mem_type);
 
         /*
          * If we need to place an LMEM resource which doesn't need CPU
          * access then we should try not to victimize mappable objects
          * first, since we likely end up stealing more of the mappable
          * portion. And likewise when we try to find space for a mappble
          * object, we know not to ever victimize objects that don't
          * occupy any mappable pages.
          */
         if (i915_ttm_cpu_maps_iomem(bo->resource) &&
             i915_ttm_buddy_man_visible_size(man) < man->size &&
             !(obj->flags & I915_BO_ALLOC_GPU_ONLY))
             bo->priority = I915_TTM_PRIO_NEEDS_CPU_ACCESS;
         else
             bo->priority = I915_TTM_PRIO_HAS_PAGES;
     }
 
     ttm_bo_move_to_lru_tail(bo);
     spin_unlock(&bo->bdev->lru_lock);
 }
 
 /*
  * TTM-backed gem object destruction requires some clarification.
  * Basically we have two possibilities here. We can either rely on the
  * i915 delayed destruction and put the TTM object when the object
  * is idle. This would be detected by TTM which would bypass the
  * TTM delayed destroy handling. The other approach is to put the TTM
  * object early and rely on the TTM destroyed handling, and then free
  * the leftover parts of the GEM object once TTM's destroyed list handling is
  * complete. For now, we rely on the latter for two reasons:
  * a) TTM can evict an object even when it's on the delayed destroy list,
  * which in theory allows for complete eviction.
  * b) There is work going on in TTM to allow freeing an object even when
  * it's not idle, and using the TTM destroyed list handling could help us
  * benefit from that.
  */
 static void i915_ttm_delayed_free(struct drm_i915_gem_object *obj)
 {
     GEM_BUG_ON(!obj->ttm.created);
 
     ttm_bo_put(i915_gem_to_ttm(obj));
 }
 
 static vm_fault_t vm_fault_ttm(struct vm_fault *vmf)
 {
     struct vm_area_struct *area = vmf->vma;
     struct ttm_buffer_object *bo = area->vm_private_data;
     struct drm_device *dev = bo->base.dev;
     struct drm_i915_gem_object *obj;
     vm_fault_t ret;
     int idx;
 
     obj = i915_ttm_to_gem(bo);
     if (!obj)
         return VM_FAULT_SIGBUS;
 
     /* Sanity check that we allow writing into this object */
     if (unlikely(i915_gem_object_is_readonly(obj) &&
              area->vm_flags & VM_WRITE))
         return VM_FAULT_SIGBUS;
 
     ret = ttm_bo_vm_reserve(bo, vmf);
     if (ret)
         return ret;
 
     if (obj->mm.madv != I915_MADV_WILLNEED) {
         dma_resv_unlock(bo->base.resv);
         return VM_FAULT_SIGBUS;
     }
 
     if (!i915_ttm_resource_mappable(bo->resource)) {
         int err = -ENODEV;
         int i;
 
         for (i = 0; i < obj->mm.n_placements; i++) {
             struct intel_memory_region *mr = obj->mm.placements[i];
             unsigned int flags;
 
             if (!mr->io_size && mr->type != INTEL_MEMORY_SYSTEM)
                 continue;
 
             flags = obj->flags;
             flags &= ~I915_BO_ALLOC_GPU_ONLY;
             err = __i915_ttm_migrate(obj, mr, flags);
             if (!err)
                 break;
         }
 
         if (err) {
             drm_dbg(dev, "Unable to make resource CPU accessible\n");
             dma_resv_unlock(bo->base.resv);
             return VM_FAULT_SIGBUS;
         }
     }
 
     if (drm_dev_enter(dev, &idx)) {
         ret = ttm_bo_vm_fault_reserved(vmf, vmf->vma->vm_page_prot,
                            TTM_BO_VM_NUM_PREFAULT);
         drm_dev_exit(idx);
     } else {
         ret = ttm_bo_vm_dummy_page(vmf, vmf->vma->vm_page_prot);
     }
     if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
         return ret;
 
     i915_ttm_adjust_lru(obj);
 
     dma_resv_unlock(bo->base.resv);
     return ret;
 }
 
 static int
 vm_access_ttm(struct vm_area_struct *area, unsigned long addr,
           void *buf, int len, int write)
 {
     struct drm_i915_gem_object *obj =
         i915_ttm_to_gem(area->vm_private_data);
 
     if (i915_gem_object_is_readonly(obj) && write)
         return -EACCES;
 
     return ttm_bo_vm_access(area, addr, buf, len, write);
 }
 
 static void ttm_vm_open(struct vm_area_struct *vma)
 {
     struct drm_i915_gem_object *obj =
         i915_ttm_to_gem(vma->vm_private_data);
 
     GEM_BUG_ON(!obj);
     i915_gem_object_get(obj);
 }
 
 static void ttm_vm_close(struct vm_area_struct *vma)
 {
     struct drm_i915_gem_object *obj =
         i915_ttm_to_gem(vma->vm_private_data);
 
     GEM_BUG_ON(!obj);
     i915_gem_object_put(obj);
 }
 
 static const struct vm_operations_struct vm_ops_ttm = {
     .fault = vm_fault_ttm,
     .access = vm_access_ttm,
     .open = ttm_vm_open,
     .close = ttm_vm_close,
 };
 
 static u64 i915_ttm_mmap_offset(struct drm_i915_gem_object *obj)
 {
     /* The ttm_bo must be allocated with I915_BO_ALLOC_USER */
     GEM_BUG_ON(!drm_mm_node_allocated(&obj->base.vma_node.vm_node));
 
     return drm_vma_node_offset_addr(&obj->base.vma_node);
 }
 
 static void i915_ttm_unmap_virtual(struct drm_i915_gem_object *obj)
 {
     ttm_bo_unmap_virtual(i915_gem_to_ttm(obj));
 }
 
 static const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = {
     .name = "i915_gem_object_ttm",
     .flags = I915_GEM_OBJECT_IS_SHRINKABLE |
          I915_GEM_OBJECT_SELF_MANAGED_SHRINK_LIST,
 
     .get_pages = i915_ttm_get_pages,
     .put_pages = i915_ttm_put_pages,
     .truncate = i915_ttm_truncate,
     .shrink = i915_ttm_shrink,
 
     .adjust_lru = i915_ttm_adjust_lru,
     .delayed_free = i915_ttm_delayed_free,
     .migrate = i915_ttm_migrate,
 
     .mmap_offset = i915_ttm_mmap_offset,
     .unmap_virtual = i915_ttm_unmap_virtual,
     .mmap_ops = &vm_ops_ttm,
 };
 
 void i915_ttm_bo_destroy(struct ttm_buffer_object *bo)
 {
     struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
 
     i915_gem_object_release_memory_region(obj);
     mutex_destroy(&obj->ttm.get_io_page.lock);
 
     if (obj->ttm.created) {
         /*
          * We freely manage the shrinker LRU outide of the mm.pages life
          * cycle. As a result when destroying the object we should be
          * extra paranoid and ensure we remove it from the LRU, before
          * we free the object.
          *
          * Touching the ttm_shrinkable outside of the object lock here
          * should be safe now that the last GEM object ref was dropped.
          */
         if (obj->mm.ttm_shrinkable)
             i915_gem_object_make_unshrinkable(obj);
 
         i915_ttm_backup_free(obj);
 
         /* This releases all gem object bindings to the backend. */
         __i915_gem_free_object(obj);
 
         call_rcu(&obj->rcu, __i915_gem_free_object_rcu);
     } else {
         __i915_gem_object_fini(obj);
     }
 }
 
 /**
  * __i915_gem_ttm_object_init - Initialize a ttm-backed i915 gem object
  * @mem: The initial memory region for the object.
  * @obj: The gem object.
  * @size: Object size in bytes.
  * @flags: gem object flags.
  *
  * Return: 0 on success, negative error code on failure.
  */
 int __i915_gem_ttm_object_init(struct intel_memory_region *mem,
                    struct drm_i915_gem_object *obj,
                    resource_size_t offset,
                    resource_size_t size,
                    resource_size_t page_size,
                    unsigned int flags)
 {
     static struct lock_class_key lock_class;
     struct drm_i915_private *i915 = mem->i915;
     struct ttm_operation_ctx ctx = {
         .interruptible = true,
         .no_wait_gpu = false,
     };
     enum ttm_bo_type bo_type;
     int ret;
 
     drm_gem_private_object_init(&i915->drm, &obj->base, size);
     i915_gem_object_init(obj, &i915_gem_ttm_obj_ops, &lock_class, flags);
 
     obj->bo_offset = offset;
 
     /* Don't put on a region list until we're either locked or fully initialized. */
     obj->mm.region = mem;
     INIT_LIST_HEAD(&obj->mm.region_link);
 
     INIT_RADIX_TREE(&obj->ttm.get_io_page.radix, GFP_KERNEL | __GFP_NOWARN);
     mutex_init(&obj->ttm.get_io_page.lock);
     bo_type = (obj->flags & I915_BO_ALLOC_USER) ? ttm_bo_type_device :
         ttm_bo_type_kernel;
 
     obj->base.vma_node.driver_private = i915_gem_to_ttm(obj);
 
     /* Forcing the page size is kernel internal only */
     GEM_BUG_ON(page_size && obj->mm.n_placements);
 
     /*
      * Keep an extra shrink pin to prevent the object from being made
      * shrinkable too early. If the ttm_tt is ever allocated in shmem, we
      * drop the pin. The TTM backend manages the shrinker LRU itself,
      * outside of the normal mm.pages life cycle.
      */
     i915_gem_object_make_unshrinkable(obj);
 
     /*
      * If this function fails, it will call the destructor, but
      * our caller still owns the object. So no freeing in the
      * destructor until obj->ttm.created is true.
      * Similarly, in delayed_destroy, we can't call ttm_bo_put()
      * until successful initialization.
      */
     ret = ttm_bo_init_reserved(&i915->bdev, i915_gem_to_ttm(obj), size,
                    bo_type, &i915_sys_placement,
                    page_size >> PAGE_SHIFT,
                    &ctx, NULL, NULL, i915_ttm_bo_destroy);
     if (ret)
         return i915_ttm_err_to_gem(ret);
 
     obj->ttm.created = true;
     i915_gem_object_release_memory_region(obj);
     i915_gem_object_init_memory_region(obj, mem);
     i915_ttm_adjust_domains_after_move(obj);
     i915_ttm_adjust_gem_after_move(obj);
     i915_gem_object_unlock(obj);
 
     return 0;
 }
 
 static const struct intel_memory_region_ops ttm_system_region_ops = {
     .init_object = __i915_gem_ttm_object_init,
     .release = intel_region_ttm_fini,
 };
 
 struct intel_memory_region *
 i915_gem_ttm_system_setup(struct drm_i915_private *i915,
               u16 type, u16 instance)
 {
     struct intel_memory_region *mr;
 
     mr = intel_memory_region_create(i915, 0,
                     totalram_pages() << PAGE_SHIFT,
                     PAGE_SIZE, 0, 0,
                     type, instance,
                     &ttm_system_region_ops);
     if (IS_ERR(mr))
         return mr;
 
     intel_memory_region_set_name(mr, "system-ttm");
     return mr;
 }

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