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linux/drivers/gpu/drm/i915/gem/selftests/i915_gem_execbuffer.c
Chris Wilson 9e0f9464e2 drm/i915/gem: Async GPU relocations only
Reduce the 3 relocation paths down to the single path that accommodates
all. The primary motivation for this is to guard the relocations with a
natural fence (derived from the i915_request used to write the
relocation from the GPU).

The tradeoff in using async gpu relocations is that it increases latency
over using direct CPU relocations, for the cases where the target is
idle and accessible by the CPU. The benefit is greatly reduced lock
contention and improved concurrency by pipelining.

Note that forcing the async gpu relocations does reveal a few issues
they have. Firstly, is that they are visible as writes to gem_busy,
causing to mark some buffers are being to written to by the GPU even
though userspace only reads. Secondly is that, in combination with the
cmdparser, they can cause priority inversions. This should be the case
where the work is being put into a common workqueue losing our priority
information and so being executed in FIFO from the worker, denying us
the opportunity to reorder the requests afterwards.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200604211457.19696-1-chris@chris-wilson.co.uk
2020-06-05 09:45:44 +01:00

162 lines
3.4 KiB
C

// SPDX-License-Identifier: MIT
/*
* Copyright © 2020 Intel Corporation
*/
#include "i915_selftest.h"
#include "gt/intel_engine_pm.h"
#include "selftests/igt_flush_test.h"
static u64 read_reloc(const u32 *map, int x, const u64 mask)
{
u64 reloc;
memcpy(&reloc, &map[x], sizeof(reloc));
return reloc & mask;
}
static int __igt_gpu_reloc(struct i915_execbuffer *eb,
struct drm_i915_gem_object *obj)
{
const unsigned int offsets[] = { 8, 3, 0 };
const u64 mask =
GENMASK_ULL(eb->reloc_cache.use_64bit_reloc ? 63 : 31, 0);
const u32 *map = page_mask_bits(obj->mm.mapping);
struct i915_request *rq;
struct i915_vma *vma;
int err;
int i;
vma = i915_vma_instance(obj, eb->context->vm, NULL);
if (IS_ERR(vma))
return PTR_ERR(vma);
err = i915_vma_pin(vma, 0, 0, PIN_USER | PIN_HIGH);
if (err)
return err;
/* 8-Byte aligned */
err = __reloc_entry_gpu(eb, vma, offsets[0] * sizeof(u32), 0);
if (err)
goto unpin_vma;
/* !8-Byte aligned */
err = __reloc_entry_gpu(eb, vma, offsets[1] * sizeof(u32), 1);
if (err)
goto unpin_vma;
/* Skip to the end of the cmd page */
i = PAGE_SIZE / sizeof(u32) - RELOC_TAIL - 1;
i -= eb->reloc_cache.rq_size;
memset32(eb->reloc_cache.rq_cmd + eb->reloc_cache.rq_size,
MI_NOOP, i);
eb->reloc_cache.rq_size += i;
/* Force batch chaining */
err = __reloc_entry_gpu(eb, vma, offsets[2] * sizeof(u32), 2);
if (err)
goto unpin_vma;
GEM_BUG_ON(!eb->reloc_cache.rq);
rq = i915_request_get(eb->reloc_cache.rq);
err = reloc_gpu_flush(&eb->reloc_cache);
if (err)
goto put_rq;
GEM_BUG_ON(eb->reloc_cache.rq);
err = i915_gem_object_wait(obj, I915_WAIT_INTERRUPTIBLE, HZ / 2);
if (err) {
intel_gt_set_wedged(eb->engine->gt);
goto put_rq;
}
if (!i915_request_completed(rq)) {
pr_err("%s: did not wait for relocations!\n", eb->engine->name);
err = -EINVAL;
goto put_rq;
}
for (i = 0; i < ARRAY_SIZE(offsets); i++) {
u64 reloc = read_reloc(map, offsets[i], mask);
if (reloc != i) {
pr_err("%s[%d]: map[%d] %llx != %x\n",
eb->engine->name, i, offsets[i], reloc, i);
err = -EINVAL;
}
}
if (err)
igt_hexdump(map, 4096);
put_rq:
i915_request_put(rq);
unpin_vma:
i915_vma_unpin(vma);
return err;
}
static int igt_gpu_reloc(void *arg)
{
struct i915_execbuffer eb;
struct drm_i915_gem_object *scratch;
int err = 0;
u32 *map;
eb.i915 = arg;
scratch = i915_gem_object_create_internal(eb.i915, 4096);
if (IS_ERR(scratch))
return PTR_ERR(scratch);
map = i915_gem_object_pin_map(scratch, I915_MAP_WC);
if (IS_ERR(map)) {
err = PTR_ERR(map);
goto err_scratch;
}
for_each_uabi_engine(eb.engine, eb.i915) {
reloc_cache_init(&eb.reloc_cache, eb.i915);
memset(map, POISON_INUSE, 4096);
intel_engine_pm_get(eb.engine);
eb.context = intel_context_create(eb.engine);
if (IS_ERR(eb.context)) {
err = PTR_ERR(eb.context);
goto err_pm;
}
err = intel_context_pin(eb.context);
if (err)
goto err_put;
err = __igt_gpu_reloc(&eb, scratch);
intel_context_unpin(eb.context);
err_put:
intel_context_put(eb.context);
err_pm:
intel_engine_pm_put(eb.engine);
if (err)
break;
}
if (igt_flush_test(eb.i915))
err = -EIO;
err_scratch:
i915_gem_object_put(scratch);
return err;
}
int i915_gem_execbuffer_live_selftests(struct drm_i915_private *i915)
{
static const struct i915_subtest tests[] = {
SUBTEST(igt_gpu_reloc),
};
if (intel_gt_is_wedged(&i915->gt))
return 0;
return i915_live_subtests(tests, i915);
}