drm/i915: Individualize fences before adding to dma_resv obj

_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
Fixes: 544460c33821 ("drm/i915: Multi-BB execbuf")
Cc: <stable@vger.kernel.org> # v5.16+
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220525095955.15371-1-nirmoy.das@intel.com

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index c326bd2..30fe847 100644 (file)
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -999,7 +999,8 @@ 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 4f6db53..0bffb70 100644 (file)
--- 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)