[Intel-gfx] [PATCH 13/28] drm/i915/gem: Add all GPU reloc awaits/signals en masse

[Chris Wilson <chris@chris-wilson.co.uk>]

Asynchronous waits and signaling form a traditional semaphore with all
the usual ordering problems with taking multiple locks. If we want to
add more than one wait on a shared resource by the GPU, we must ensure
that all the associated timelines are advanced atomically, ergo we must
lock all the timelines en masse.

Testcase: igt/gem_exec_reloc/basic-concurrent16
Fixes: 0e97fbb08055 ("drm/i915/gem: Use a single chained reloc batches for a single execbuf")
References: https://gitlab.freedesktop.org/drm/intel/-/issues/1889
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 114 ++++++++++++------
 .../i915/gem/selftests/i915_gem_execbuffer.c  |  24 ++--
 2 files changed, 93 insertions(+), 45 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 83cea2ea7c61..8f3c1cf5af31 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -259,7 +259,6 @@ struct i915_execbuffer {
 		bool has_fence : 1;
 		bool needs_unfenced : 1;
 
-		struct i915_vma *target;
 		struct i915_request *rq;
 		struct i915_vma *rq_vma;
 		u32 *rq_cmd;
@@ -924,7 +923,6 @@ static void reloc_cache_init(struct reloc_cache *cache,
 	cache->has_fence = cache->gen < 4;
 	cache->needs_unfenced = INTEL_INFO(i915)->unfenced_needs_alignment;
 	cache->node.flags = 0;
-	cache->target = NULL;
 }
 
 #define RELOC_TAIL 4
@@ -1038,26 +1036,6 @@ static void reloc_gpu_flush(struct reloc_cache *cache)
 	i915_request_add(rq);
 }
 
-static int reloc_move_to_gpu(struct i915_request *rq, struct i915_vma *vma)
-{
-	struct drm_i915_gem_object *obj = vma->obj;
-	int err;
-
-	i915_vma_lock(vma);
-
-	if (obj->cache_dirty & ~obj->cache_coherent)
-		i915_gem_clflush_object(obj, 0);
-	obj->write_domain = 0;
-
-	err = i915_request_await_object(rq, vma->obj, true);
-	if (err == 0)
-		err = i915_vma_move_to_active(vma, rq, EXEC_OBJECT_WRITE);
-
-	i915_vma_unlock(vma);
-
-	return err;
-}
-
 static int
 __reloc_gpu_alloc(struct i915_execbuffer *eb, struct intel_engine_cs *engine)
 {
@@ -1147,24 +1125,12 @@ __reloc_gpu_alloc(struct i915_execbuffer *eb, struct intel_engine_cs *engine)
 	return err;
 }
 
-static u32 *reloc_batch_grow(struct i915_execbuffer *eb,
-			     struct i915_vma *vma,
-			     unsigned int len)
+static u32 *reloc_batch_grow(struct i915_execbuffer *eb, unsigned int len)
 {
 	struct reloc_cache *cache = &eb->reloc_cache;
 	u32 *cmd;
 	int err;
 
-	if (vma != cache->target) {
-		err = reloc_move_to_gpu(cache->rq, vma);
-		if (unlikely(err)) {
-			i915_request_set_error_once(cache->rq, err);
-			return ERR_PTR(err);
-		}
-
-		cache->target = vma;
-	}
-
 	if (unlikely(cache->rq_size + len >
 		     PAGE_SIZE / sizeof(u32) - RELOC_TAIL)) {
 		err = reloc_gpu_chain(cache);
@@ -1210,7 +1176,7 @@ static int __reloc_entry_gpu(struct i915_execbuffer *eb,
 	else
 		len = 3;
 
-	batch = reloc_batch_grow(eb, vma, len);
+	batch = reloc_batch_grow(eb, len);
 	if (IS_ERR(batch))
 		return PTR_ERR(batch);
 
@@ -1471,6 +1437,78 @@ static long eb_reloc_vma(struct i915_execbuffer *eb, struct eb_vma *ev,
 	return required;
 }
 
+static int reloc_move_to_gpu(struct reloc_cache *cache, struct eb_vma *ev)
+{
+	struct i915_request *rq = cache->rq;
+	struct i915_vma *vma = ev->vma;
+	struct drm_i915_gem_object *obj = vma->obj;
+	int err;
+
+	if (obj->cache_dirty & ~obj->cache_coherent)
+		i915_gem_clflush_object(obj, 0);
+
+	obj->write_domain = I915_GEM_DOMAIN_RENDER;
+	obj->read_domains = I915_GEM_DOMAIN_RENDER;
+
+	err = i915_request_await_object(rq, obj, true);
+	if (err)
+		return err;
+
+	err = __i915_vma_move_to_active(vma, rq);
+	if (err)
+		return err;
+
+	dma_resv_add_excl_fence(vma->resv, &rq->fence);
+
+	return 0;
+}
+
+static int
+lock_relocs(struct i915_execbuffer *eb)
+{
+	struct ww_acquire_ctx acquire;
+	struct eb_vma *ev;
+	int err = 0;
+
+	ww_acquire_init(&acquire, &reservation_ww_class);
+
+	list_for_each_entry(ev, &eb->relocs, reloc_link) {
+		struct i915_vma *vma = ev->vma;
+
+		err = ww_mutex_lock_interruptible(&vma->resv->lock, &acquire);
+		if (err == -EDEADLK) {
+			struct eb_vma *unlock = ev, *en;
+
+			list_for_each_entry_safe_continue_reverse(unlock, en,
+								  &eb->relocs,
+								  reloc_link) {
+				ww_mutex_unlock(&unlock->vma->resv->lock);
+				list_move_tail(&unlock->reloc_link,
+					       &eb->relocs);
+			}
+
+			GEM_BUG_ON(!list_is_first(&ev->reloc_link,
+						  &eb->relocs));
+			err = ww_mutex_lock_slow_interruptible(&vma->resv->lock,
+							       &acquire);
+		}
+		if (err)
+			break;
+	}
+
+	ww_acquire_done(&acquire);
+
+	list_for_each_entry_continue_reverse(ev, &eb->relocs, reloc_link) {
+		if (err == 0)
+			err = reloc_move_to_gpu(&eb->reloc_cache, ev);
+		ww_mutex_unlock(&ev->vma->resv->lock);
+	}
+
+	ww_acquire_fini(&acquire);
+
+	return err;
+}
+
 static bool reloc_can_use_engine(const struct intel_engine_cs *engine)
 {
 	return engine->class != VIDEO_DECODE_CLASS || !IS_GEN(engine->i915, 6);
@@ -1499,6 +1537,10 @@ static int reloc_gpu(struct i915_execbuffer *eb)
 		return err;
 	GEM_BUG_ON(!eb->reloc_cache.rq);
 
+	err = lock_relocs(eb);
+	if (err)
+		goto out;
+
 	err = reloc_gpu_emit(&eb->reloc_cache);
 	if (err)
 		goto out;
diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_execbuffer.c
index faed6480a792..4f10b51f9a7e 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_execbuffer.c
@@ -24,15 +24,15 @@ static int __igt_gpu_reloc(struct i915_execbuffer *eb,
 		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;
+	struct eb_vma ev;
 	int err;
 	int i;
 
-	vma = i915_vma_instance(obj, eb->context->vm, NULL);
-	if (IS_ERR(vma))
-		return PTR_ERR(vma);
+	ev.vma = i915_vma_instance(obj, eb->context->vm, NULL);
+	if (IS_ERR(ev.vma))
+		return PTR_ERR(ev.vma);
 
-	err = i915_vma_pin(vma, 0, 0, PIN_USER | PIN_HIGH);
+	err = i915_vma_pin(ev.vma, 0, 0, PIN_USER | PIN_HIGH);
 	if (err)
 		return err;
 
@@ -40,17 +40,22 @@ static int __igt_gpu_reloc(struct i915_execbuffer *eb,
 	if (err)
 		goto unpin_vma;
 
+	list_add(&ev.reloc_link, &eb->relocs);
+	err = lock_relocs(eb);
+	if (err)
+		goto unpin_vma;
+
 	err = reloc_gpu_emit(&eb->reloc_cache);
 	if (err)
 		goto unpin_vma;
 
 	/* 8-Byte aligned */
-	err = __reloc_entry_gpu(eb, vma, offsets[0] * sizeof(u32), 0);
+	err = __reloc_entry_gpu(eb, ev.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);
+	err = __reloc_entry_gpu(eb, ev.vma, offsets[1] * sizeof(u32), 1);
 	if (err)
 		goto unpin_vma;
 
@@ -62,7 +67,7 @@ static int __igt_gpu_reloc(struct i915_execbuffer *eb,
 	eb->reloc_cache.rq_size += i;
 
 	/* Force batch chaining */
-	err = __reloc_entry_gpu(eb, vma, offsets[2] * sizeof(u32), 2);
+	err = __reloc_entry_gpu(eb, ev.vma, offsets[2] * sizeof(u32), 2);
 	if (err)
 		goto unpin_vma;
 
@@ -97,7 +102,7 @@ static int __igt_gpu_reloc(struct i915_execbuffer *eb,
 put_rq:
 	i915_request_put(rq);
 unpin_vma:
-	i915_vma_unpin(vma);
+	i915_vma_unpin(ev.vma);
 	return err;
 }
 
@@ -121,6 +126,7 @@ static int igt_gpu_reloc(void *arg)
 	}
 
 	for_each_uabi_engine(eb.engine, eb.i915) {
+		INIT_LIST_HEAD(&eb.relocs);
 		reloc_cache_init(&eb.reloc_cache, eb.i915);
 		memset(map, POISON_INUSE, 4096);
 
-- 
2.20.1

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