drivers/gpu/drm/i915/i915_gem_batch_pool.c

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright © 2014-2018 Intel Corporation
   5  */
   6
   7 #include "i915_gem_batch_pool.h"
   8 #include "i915_drv.h"
   9
  10 /**
  11  * DOC: batch pool
  12  *
  13  * In order to submit batch buffers as 'secure', the software command parser
  14  * must ensure that a batch buffer cannot be modified after parsing. It does
  15  * this by copying the user provided batch buffer contents to a kernel owned
  16  * buffer from which the hardware will actually execute, and by carefully
  17  * managing the address space bindings for such buffers.
  18  *
  19  * The batch pool framework provides a mechanism for the driver to manage a
  20  * set of scratch buffers to use for this purpose. The framework can be
  21  * extended to support other uses cases should they arise.
  22  */
  23
  24 /**
  25  * i915_gem_batch_pool_init() - initialize a batch buffer pool
  26  * @pool: the batch buffer pool
  27  * @engine: the associated request submission engine
  28  */
  29 void i915_gem_batch_pool_init(struct i915_gem_batch_pool *pool,
  30                               struct intel_engine_cs *engine)
  31 {
  32         int n;
  33
  34         pool->engine = engine;
  35
  36         for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++)
  37                 INIT_LIST_HEAD(&pool->cache_list[n]);
  38 }
  39
  40 /**
  41  * i915_gem_batch_pool_fini() - clean up a batch buffer pool
  42  * @pool: the pool to clean up
  43  *
  44  * Note: Callers must hold the struct_mutex.
  45  */
  46 void i915_gem_batch_pool_fini(struct i915_gem_batch_pool *pool)
  47 {
  48         int n;
  49
  50         lockdep_assert_held(&pool->engine->i915->drm.struct_mutex);
  51
  52         for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++) {
  53                 struct drm_i915_gem_object *obj, *next;
  54
  55                 list_for_each_entry_safe(obj, next,
  56                                          &pool->cache_list[n],
  57                                          batch_pool_link)
  58                         __i915_gem_object_release_unless_active(obj);
  59
  60                 INIT_LIST_HEAD(&pool->cache_list[n]);
  61         }
  62 }
  63
  64 /**
  65  * i915_gem_batch_pool_get() - allocate a buffer from the pool
  66  * @pool: the batch buffer pool
  67  * @size: the minimum desired size of the returned buffer
  68  *
  69  * Returns an inactive buffer from @pool with at least @size bytes,
  70  * with the pages pinned. The caller must i915_gem_object_unpin_pages()
  71  * on the returned object.
  72  *
  73  * Note: Callers must hold the struct_mutex
  74  *
  75  * Return: the buffer object or an error pointer
  76  */
  77 struct drm_i915_gem_object *
  78 i915_gem_batch_pool_get(struct i915_gem_batch_pool *pool,
  79                         size_t size)
  80 {
  81         struct drm_i915_gem_object *obj;
  82         struct list_head *list;
  83         int n, ret;
  84
  85         lockdep_assert_held(&pool->engine->i915->drm.struct_mutex);
  86
  87         /* Compute a power-of-two bucket, but throw everything greater than
  88          * 16KiB into the same bucket: i.e. the the buckets hold objects of
  89          * (1 page, 2 pages, 4 pages, 8+ pages).
  90          */
  91         n = fls(size >> PAGE_SHIFT) - 1;
  92         if (n >= ARRAY_SIZE(pool->cache_list))
  93                 n = ARRAY_SIZE(pool->cache_list) - 1;
  94         list = &pool->cache_list[n];
  95
  96         list_for_each_entry(obj, list, batch_pool_link) {
  97                 /* The batches are strictly LRU ordered */
  98                 if (i915_gem_object_is_active(obj)) {
  99                         struct reservation_object *resv = obj->resv;
 100
 101                         if (!reservation_object_test_signaled_rcu(resv, true))
 102                                 break;
 103
 104                         i915_retire_requests(pool->engine->i915);
 105                         GEM_BUG_ON(i915_gem_object_is_active(obj));
 106
 107                         /*
 108                          * The object is now idle, clear the array of shared
 109                          * fences before we add a new request. Although, we
 110                          * remain on the same engine, we may be on a different
 111                          * timeline and so may continually grow the array,
 112                          * trapping a reference to all the old fences, rather
 113                          * than replace the existing fence.
 114                          */
 115                         if (rcu_access_pointer(resv->fence)) {
 116                                 reservation_object_lock(resv, NULL);
 117                                 reservation_object_add_excl_fence(resv, NULL);
 118                                 reservation_object_unlock(resv);
 119                         }
 120                 }
 121
 122                 GEM_BUG_ON(!reservation_object_test_signaled_rcu(obj->resv,
 123                                                                  true));
 124
 125                 if (obj->base.size >= size)
 126                         goto found;
 127         }
 128
 129         obj = i915_gem_object_create_internal(pool->engine->i915, size);
 130         if (IS_ERR(obj))
 131                 return obj;
 132
 133 found:
 134         ret = i915_gem_object_pin_pages(obj);
 135         if (ret)
 136                 return ERR_PTR(ret);
 137
 138         list_move_tail(&obj->batch_pool_link, list);
 139         return obj;
 140 }