[Intel-gfx] [PATCH 23/25] drm/i915: Update I915_GEM_BUSY IOCTL to understand composite fences

Matthew Brost
2021-10-14T17:47:48Z

Parallel submission create composite fences (dma_fence_array) for excl /
shared slots in objects. The I915_GEM_BUSY IOCTL checks these slots to
determine the busyness of the object. Prior to patch it only check if
the fence in the slot was a i915_request. Update the check to understand
composite fences and correctly report the busyness.

v2:
(Tvrtko)
- Remove duplicate BUILD_BUG_ON

Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
drivers/gpu/drm/i915/gem/i915_gem_busy.c | 57 +++++++++++++++----
.../gpu/drm/i915/gem/i915_gem_execbuffer.c | 5 +-
drivers/gpu/drm/i915/i915_request.h | 6 ++
3 files changed, 55 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
index 6234e17259c1..7358bebef15c 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
@@ -4,6 +4,8 @@
* Copyright © 2014-2016 Intel Corporation
*/

+#include <linux/dma-fence-array.h>
+
#include "gt/intel_engine.h"

#include "i915_gem_ioctls.h"
@@ -36,7 +38,7 @@ static __always_inline u32 __busy_write_id(u16 id)
}

static __always_inline unsigned int
-__busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u16 id))
+__busy_set_if_active(struct dma_fence *fence, u32 (*flag)(u16 id))
{
const struct i915_request *rq;

@@ -46,29 +48,60 @@ __busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u16 id))
* to eventually flush us, but to minimise latency just ask the
* hardware.
*
- * Note we only report on the status of native fences.
+ * Note we only report on the status of native fences and we currently
+ * have two native fences:
+ *
+ * 1. A composite fence (dma_fence_array) constructed of i915 requests
+ * created during a parallel submission. In this case we deconstruct the
+ * composite fence into individual i915 requests and check the status of
+ * each request.
+ *
+ * 2. A single i915 request.
*/
- if (!dma_fence_is_i915(fence))
+ if (dma_fence_is_array(fence)) {
+ struct dma_fence_array *array = to_dma_fence_array(fence);
+ struct dma_fence **child = array->fences;
+ unsigned int nchild = array->num_fences;
+
+ do {
+ struct dma_fence *current_fence = *child++;
+
+ /* Not an i915 fence, can't be busy per above */
+ if (!dma_fence_is_i915(current_fence) ||
+ !test_bit(I915_FENCE_FLAG_COMPOSITE,
+ &current_fence->flags)) {
+ return 0;
+ }
+
+ rq = to_request(current_fence);
+ if (!i915_request_completed(rq))
+ return flag(rq->engine->uabi_class);
+ } while (--nchild);
+
+ /* All requests in array complete, not busy */
return 0;
+ } else {
+ 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;
+ rq = to_request(fence);
+ if (i915_request_completed(rq))
+ return 0;

- /* Beware type-expansion follies! */
- BUILD_BUG_ON(!typecheck(u16, rq->engine->uabi_class));
- return flag(rq->engine->uabi_class);
+ /* Beware type-expansion follies! */
+ BUILD_BUG_ON(!typecheck(u16, rq->engine->uabi_class));
+ return flag(rq->engine->uabi_class);
+ }
}

static __always_inline unsigned int
-busy_check_reader(const struct dma_fence *fence)
+busy_check_reader(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)
+busy_check_writer(struct dma_fence *fence)
{
if (!fence)
return 0;
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index fc30856e81fa..1231224728e4 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -3008,8 +3008,11 @@ eb_composite_fence_create(struct i915_execbuffer *eb, int out_fence_fd)
if (!fences)
return ERR_PTR(-ENOMEM);

- for_each_batch_create_order(eb, i)
+ for_each_batch_create_order(eb, i) {
fences[i] = &eb->requests[i]->fence;
+ __set_bit(I915_FENCE_FLAG_COMPOSITE,
+ &eb->requests[i]->fence.flags);
+ }

fence_array = dma_fence_array_create(eb->num_batches,
fences,
diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
index 24db8459376b..dc359242d1ae 100644
--- a/drivers/gpu/drm/i915/i915_request.h
+++ b/drivers/gpu/drm/i915/i915_request.h
@@ -156,6 +156,12 @@ enum {
* submission / relationship encoutered an error.
*/
I915_FENCE_FLAG_SKIP_PARALLEL,
+
+ /*
+ * I915_FENCE_FLAG_COMPOSITE - Indicates fence is part of a composite
+ * fence (dma_fence_array) and i915 generated for parallel submission.
+ */
+ I915_FENCE_FLAG_COMPOSITE,
};

/**
--
2.32.0