drm/i915: Move GEM activity tracking into a common struct reservation_object

In preparation to support many distinct timelines, we need to expand the
activity tracking on the GEM object to handle more than just a request
per engine. We already use the struct reservation_object on the dma-buf
to handle many fence contexts, so integrating that into the GEM object
itself is the preferred solution. (For example, we can now share the same
reservation_object between every consumer/producer using this buffer and
skip the manual import/export via dma-buf.)

v2: Reimplement busy-ioctl (by walking the reservation object), postpone
the ABI change for another day. Similarly use the reservation object to
find the last_write request (if active and from i915) for choosing
display CS flips.

Caveats:

 * busy-ioctl: busy-ioctl only reports on the native fences, it will not
warn of stalls (in set-domain-ioctl, pread/pwrite etc) if the object is
being rendered to by external fences. It also will not report the same
busy state as wait-ioctl (or polling on the dma-buf) in the same
circumstances. On the plus side, it does retain reporting of which
*i915* engines are engaged with this object.

 * non-blocking atomic modesets take a step backwards as the wait for
render completion blocks the ioctl. This is fixed in a subsequent
patch to use a fence instead for awaiting on the rendering, see
"drm/i915: Restore nonblocking awaits for modesetting"

 * dynamic array manipulation for shared-fences in reservation is slower
than the previous lockless static assignment (e.g. gem_exec_lut_handle
runtime on ivb goes from 42s to 66s), mainly due to atomic operations
(maintaining the fence refcounts).

 * loss of object-level retirement callbacks, emulated by VMA retirement
tracking.

 * minor loss of object-level last activity information from debugfs,
could be replaced with per-vma information if desired

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161028125858.23563-21-chris@chris-wilson.co.uk

1 files changed, 3 insertions, 50 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
index 4d45f20d11ed..5e38299b5df6 100644
--- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
@@ -211,60 +211,17 @@ static const struct dma_buf_ops i915_dmabuf_ops =  {
 	.end_cpu_access = i915_gem_end_cpu_access,
 };
 
-static void export_fences(struct drm_i915_gem_object *obj,
-			  struct dma_buf *dma_buf)
-{
-	struct reservation_object *resv = dma_buf->resv;
-	struct drm_i915_gem_request *req;
-	unsigned long active;
-	int idx;
-
-	active = __I915_BO_ACTIVE(obj);
-	if (!active)
-		return;
-
-	/* Serialise with execbuf to prevent concurrent fence-loops */
-	mutex_lock(&obj->base.dev->struct_mutex);
-
-	/* Mark the object for future fences before racily adding old fences */
-	obj->base.dma_buf = dma_buf;
-
-	ww_mutex_lock(&resv->lock, NULL);
-
-	for_each_active(active, idx) {
-		req = i915_gem_active_get(&obj->last_read[idx],
-					  &obj->base.dev->struct_mutex);
-		if (!req)
-			continue;
-
-		if (reservation_object_reserve_shared(resv) == 0)
-			reservation_object_add_shared_fence(resv, &req->fence);
-
-		i915_gem_request_put(req);
-	}
-
-	req = i915_gem_active_get(&obj->last_write,
-				  &obj->base.dev->struct_mutex);
-	if (req) {
-		reservation_object_add_excl_fence(resv, &req->fence);
-		i915_gem_request_put(req);
-	}
-
-	ww_mutex_unlock(&resv->lock);
-	mutex_unlock(&obj->base.dev->struct_mutex);
-}
-
 struct dma_buf *i915_gem_prime_export(struct drm_device *dev,
 				      struct drm_gem_object *gem_obj, int flags)
 {
 	struct drm_i915_gem_object *obj = to_intel_bo(gem_obj);
 	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
-	struct dma_buf *dma_buf;
 
 	exp_info.ops = &i915_dmabuf_ops;
 	exp_info.size = gem_obj->size;
 	exp_info.flags = flags;
 	exp_info.priv = gem_obj;
+	exp_info.resv = obj->resv;
 
 	if (obj->ops->dmabuf_export) {
 		int ret = obj->ops->dmabuf_export(obj);
@@ -272,12 +229,7 @@ struct dma_buf *i915_gem_prime_export(struct drm_device *dev,
 			return ERR_PTR(ret);
 	}
 
-	dma_buf = drm_gem_dmabuf_export(dev, &exp_info);
-	if (IS_ERR(dma_buf))
-		return dma_buf;
-
-	export_fences(obj, dma_buf);
-	return dma_buf;
+	return drm_gem_dmabuf_export(dev, &exp_info);
 }
 
 static struct sg_table *
@@ -335,6 +287,7 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
 	drm_gem_private_object_init(dev, &obj->base, dma_buf->size);
 	i915_gem_object_init(obj, &i915_gem_object_dmabuf_ops);
 	obj->base.import_attach = attach;
+	obj->resv = dma_buf->resv;
 
 	/* We use GTT as shorthand for a coherent domain, one that is
 	 * neither in the GPU cache nor in the CPU cache, where all