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 */
i915_gem_batch_pool_init(struct i915_gem_batch_pool * pool,struct intel_engine_cs * engine)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 */
i915_gem_batch_pool_fini(struct i915_gem_batch_pool * pool)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 *
i915_gem_batch_pool_get(struct i915_gem_batch_pool * pool,size_t size)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 }
141
