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/*
* SPDX-License-Identifier: MIT
*
* Copyright © 2014-2018 Intel Corporation
*/
#include "i915_gem_batch_pool.h"
#include "i915_drv.h"
/**
* DOC: batch pool
*
* In order to submit batch buffers as 'secure', the software command parser
* must ensure that a batch buffer cannot be modified after parsing. It does
* this by copying the user provided batch buffer contents to a kernel owned
* buffer from which the hardware will actually execute, and by carefully
* managing the address space bindings for such buffers.
*
* The batch pool framework provides a mechanism for the driver to manage a
* set of scratch buffers to use for this purpose. The framework can be
* extended to support other uses cases should they arise.
*/
/**
* i915_gem_batch_pool_init() - initialize a batch buffer pool
* @pool: the batch buffer pool
* @engine: the associated request submission engine
*/
void i915_gem_batch_pool_init(struct i915_gem_batch_pool *pool,
struct intel_engine_cs *engine)
{
int n;
pool->engine = engine;
for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++)
INIT_LIST_HEAD(&pool->cache_list[n]);
}
/**
* i915_gem_batch_pool_fini() - clean up a batch buffer pool
* @pool: the pool to clean up
*
* Note: Callers must hold the struct_mutex.
*/
void i915_gem_batch_pool_fini(struct i915_gem_batch_pool *pool)
{
int n;
lockdep_assert_held(&pool->engine->i915->drm.struct_mutex);
for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++) {
struct drm_i915_gem_object *obj, *next;
list_for_each_entry_safe(obj, next,
&pool->cache_list[n],
batch_pool_link)
i915_gem_object_put(obj);
INIT_LIST_HEAD(&pool->cache_list[n]);
}
}
/**
* i915_gem_batch_pool_get() - allocate a buffer from the pool
* @pool: the batch buffer pool
* @size: the minimum desired size of the returned buffer
*
* Returns an inactive buffer from @pool with at least @size bytes,
* with the pages pinned. The caller must i915_gem_object_unpin_pages()
* on the returned object.
*
* Note: Callers must hold the struct_mutex
*
* Return: the buffer object or an error pointer
*/
struct drm_i915_gem_object *
i915_gem_batch_pool_get(struct i915_gem_batch_pool *pool,
size_t size)
{
struct drm_i915_gem_object *obj;
struct list_head *list;
int n, ret;
lockdep_assert_held(&pool->engine->i915->drm.struct_mutex);
/* Compute a power-of-two bucket, but throw everything greater than
* 16KiB into the same bucket: i.e. the the buckets hold objects of
* (1 page, 2 pages, 4 pages, 8+ pages).
*/
n = fls(size >> PAGE_SHIFT) - 1;
if (n >= ARRAY_SIZE(pool->cache_list))
n = ARRAY_SIZE(pool->cache_list) - 1;
list = &pool->cache_list[n];
list_for_each_entry(obj, list, batch_pool_link) {
struct reservation_object *resv = obj->base.resv;
/* The batches are strictly LRU ordered */
if (!reservation_object_test_signaled_rcu(resv, true))
break;
/*
* The object is now idle, clear the array of shared
* fences before we add a new request. Although, we
* remain on the same engine, we may be on a different
* timeline and so may continually grow the array,
* trapping a reference to all the old fences, rather
* than replace the existing fence.
*/
if (rcu_access_pointer(resv->fence)) {
reservation_object_lock(resv, NULL);
reservation_object_add_excl_fence(resv, NULL);
reservation_object_unlock(resv);
}
if (obj->base.size >= size)
goto found;
}
obj = i915_gem_object_create_internal(pool->engine->i915, size);
if (IS_ERR(obj))
return obj;
found:
ret = i915_gem_object_pin_pages(obj);
if (ret)
return ERR_PTR(ret);
list_move_tail(&obj->batch_pool_link, list);
return obj;
}
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