Re: [PATCH v6] drm/i915: Individualize fences before adding to dma_resv obj

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On 27/05/2022 10:46, Das, Nirmoy wrote:

On 5/26/2022 11:27 AM, Matthew Auld wrote:
On 25/05/2022 10:59, Nirmoy Das wrote:
_i915_vma_move_to_active() can receive > 1 fences for
multiple batch buffers submission. Because dma_resv_add_fence()
can only accept one fence at a time, change _i915_vma_move_to_active()
to be aware of multiple fences so that it can add individual
fences to the dma resv object.

v6: fix multi-line comment.
v5: remove double fence reservation for batch VMAs.
v4: Reserve fences for composite_fence on multi-batch contexts and
     also reserve fence slots to composite_fence for each VMAs.
v3: dma_resv_reserve_fences is not cumulative so pass num_fences.
v2: make sure to reserve enough fence slots before adding.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5614
Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx>

Do we need Fixes: ?


We can add:

Fixes: 544460c33821 ("drm/i915: Multi-BB execbuf")

Ok, so needs:

Fixes: 544460c33821 ("drm/i915: Multi-BB execbuf")
Cc: <stable@xxxxxxxxxxxxxxx> # v5.16+

Should I go ahead and push this to gt-next?



Regards,

Nirmoy



---
  .../gpu/drm/i915/gem/i915_gem_execbuffer.c    |  3 +-
  drivers/gpu/drm/i915/i915_vma.c               | 48 +++++++++++--------
  2 files changed, 30 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index b279588c0672..8880d38d36b6 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -1010,7 +1010,8 @@ static int eb_validate_vmas(struct i915_execbuffer *eb)
              }
          }
  -        err = dma_resv_reserve_fences(vma->obj->base.resv, 1);
+        /* Reserve enough slots to accommodate composite fences */
+        err = dma_resv_reserve_fences(vma->obj->base.resv, eb->num_batches);
          if (err)
              return err;
  diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 4f6db539571a..0bffb70b3c5f 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -23,6 +23,7 @@
   */
    #include <linux/sched/mm.h>
+#include <linux/dma-fence-array.h>
  #include <drm/drm_gem.h>
    #include "display/intel_frontbuffer.h"
@@ -1823,6 +1824,21 @@ int _i915_vma_move_to_active(struct i915_vma *vma,
      if (unlikely(err))
          return err;
  +    /*
+     * Reserve fences slot early to prevent an allocation after preparing
+     * the workload and associating fences with dma_resv.
+     */
+    if (fence && !(flags & __EXEC_OBJECT_NO_RESERVE)) {
+        struct dma_fence *curr;
+        int idx;
+
+        dma_fence_array_for_each(curr, idx, fence)
+            ;
+        err = dma_resv_reserve_fences(vma->obj->base.resv, idx);
+        if (unlikely(err))
+            return err;
+    }
+
      if (flags & EXEC_OBJECT_WRITE) {
          struct intel_frontbuffer *front;
  @@ -1832,31 +1848,23 @@ int _i915_vma_move_to_active(struct i915_vma *vma,
                  i915_active_add_request(&front->write, rq);
              intel_frontbuffer_put(front);
          }
+    }
  -        if (!(flags & __EXEC_OBJECT_NO_RESERVE)) {
-            err = dma_resv_reserve_fences(vma->obj->base.resv, 1);
-            if (unlikely(err))
-                return err;
-        }
+    if (fence) {
+        struct dma_fence *curr;
+        enum dma_resv_usage usage;
+        int idx;
  -        if (fence) {
-            dma_resv_add_fence(vma->obj->base.resv, fence,
-                       DMA_RESV_USAGE_WRITE);
+        obj->read_domains = 0;
+        if (flags & EXEC_OBJECT_WRITE) {
+            usage = DMA_RESV_USAGE_WRITE;
              obj->write_domain = I915_GEM_DOMAIN_RENDER;
-            obj->read_domains = 0;
-        }
-    } else {
-        if (!(flags & __EXEC_OBJECT_NO_RESERVE)) {
-            err = dma_resv_reserve_fences(vma->obj->base.resv, 1);
-            if (unlikely(err))
-                return err;
+        } else {
+            usage = DMA_RESV_USAGE_READ;
          }
  -        if (fence) {
-            dma_resv_add_fence(vma->obj->base.resv, fence,
-                       DMA_RESV_USAGE_READ);
-            obj->write_domain = 0;
-        }
+        dma_fence_array_for_each(curr, idx, fence)
+            dma_resv_add_fence(vma->obj->base.resv, curr, usage);
      }
        if (flags & EXEC_OBJECT_NEEDS_FENCE && vma->fence)



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