1 files changed, 139 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
new file mode 100644
index 000000000000..6ad93a09968c
--- /dev/null
+++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
@@ -0,0 +1,139 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2014-2016 Intel Corporation
+ */
+
+#include "gt/intel_engine.h"
+
+#include "i915_gem_ioctls.h"
+#include "i915_gem_object.h"
+
+static __always_inline u32 __busy_read_flag(u8 id)
+{
+	if (id == (u8)I915_ENGINE_CLASS_INVALID)
+		return 0xffff0000u;
+
+	GEM_BUG_ON(id >= 16);
+	return 0x10000u << id;
+}
+
+static __always_inline u32 __busy_write_id(u8 id)
+{
+	/*
+	 * The uABI guarantees an active writer is also amongst the read
+	 * engines. This would be true if we accessed the activity tracking
+	 * under the lock, but as we perform the lookup of the object and
+	 * its activity locklessly we can not guarantee that the last_write
+	 * being active implies that we have set the same engine flag from
+	 * last_read - hence we always set both read and write busy for
+	 * last_write.
+	 */
+	if (id == (u8)I915_ENGINE_CLASS_INVALID)
+		return 0xffffffffu;
+
+	return (id + 1) | __busy_read_flag(id);
+}
+
+static __always_inline unsigned int
+__busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u8 id))
+{
+	const struct i915_request *rq;
+
+	/*
+	 * We have to check the current hw status of the fence as the uABI
+	 * guarantees forward progress. We could rely on the idle worker
+	 * to eventually flush us, but to minimise latency just ask the
+	 * hardware.
+	 *
+	 * Note we only report on the status of native fences.
+	 */
+	if (!dma_fence_is_i915(fence))
+		return 0;
+
+	/* opencode to_request() in order to avoid const warnings */
+	rq = container_of(fence, const struct i915_request, fence);
+	if (i915_request_completed(rq))
+		return 0;
+
+	/* Beware type-expansion follies! */
+	BUILD_BUG_ON(!typecheck(u8, rq->engine->uabi_class));
+	return flag(rq->engine->uabi_class);
+}
+
+static __always_inline unsigned int
+busy_check_reader(const struct dma_fence *fence)
+{
+	return __busy_set_if_active(fence, __busy_read_flag);
+}
+
+static __always_inline unsigned int
+busy_check_writer(const struct dma_fence *fence)
+{
+	if (!fence)
+		return 0;
+
+	return __busy_set_if_active(fence, __busy_write_id);
+}
+
+int
+i915_gem_busy_ioctl(struct drm_device *dev, void *data,
+		    struct drm_file *file)
+{
+	struct drm_i915_gem_busy *args = data;
+	struct drm_i915_gem_object *obj;
+	struct reservation_object_list *list;
+	unsigned int seq;
+	int err;
+
+	err = -ENOENT;
+	rcu_read_lock();
+	obj = i915_gem_object_lookup_rcu(file, args->handle);
+	if (!obj)
+		goto out;
+
+	/*
+	 * A discrepancy here is that we do not report the status of
+	 * non-i915 fences, i.e. even though we may report the object as idle,
+	 * a call to set-domain may still stall waiting for foreign rendering.
+	 * This also means that wait-ioctl may report an object as busy,
+	 * where busy-ioctl considers it idle.
+	 *
+	 * We trade the ability to warn of foreign fences to report on which
+	 * i915 engines are active for the object.
+	 *
+	 * Alternatively, we can trade that extra information on read/write
+	 * activity with
+	 *	args->busy =
+	 *		!reservation_object_test_signaled_rcu(obj->resv, true);
+	 * to report the overall busyness. This is what the wait-ioctl does.
+	 *
+	 */
+retry:
+	seq = raw_read_seqcount(&obj->base.resv->seq);
+
+	/* Translate the exclusive fence to the READ *and* WRITE engine */
+	args->busy =
+		busy_check_writer(rcu_dereference(obj->base.resv->fence_excl));
+
+	/* Translate shared fences to READ set of engines */
+	list = rcu_dereference(obj->base.resv->fence);
+	if (list) {
+		unsigned int shared_count = list->shared_count, i;
+
+		for (i = 0; i < shared_count; ++i) {
+			struct dma_fence *fence =
+				rcu_dereference(list->shared[i]);
+
+			args->busy |= busy_check_reader(fence);
+		}
+	}
+
+	if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq))
+		goto retry;
+
+	err = 0;
+out:
+	rcu_read_unlock();
+	return err;
+}