drm/i915: Purge loose pages if we run out of DMA remap space

If the DMA remap fails, one cause can be that we have too many objects
pinned in a small remapping table, such as swiotlb. (DMA remapping does
not trigger the shrinker by itself on its normal failure paths.)  So try
purging all other objects (using i915_gem_shrink_all(), sparing our own
pages as we have yet to assign them to the obj->pages) and try again. If
there are no pages to reclaim (and consequently no pages to unmap), the
shrinker will report 0 and we fail with -ENOSPC as before.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170106152240.5793-2-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 00520f2..f698006 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -2361,10 +2361,24 @@ void i915_gem_suspend_gtt_mappings(struct drm_i915_private *dev_priv)
 int i915_gem_gtt_prepare_pages(struct drm_i915_gem_object *obj,
                               struct sg_table *pages)
 {
-       if (dma_map_sg(&obj->base.dev->pdev->dev,
-                      pages->sgl, pages->nents,
-                      PCI_DMA_BIDIRECTIONAL))
-               return 0;
+       do {
+               if (dma_map_sg(&obj->base.dev->pdev->dev,
+                              pages->sgl, pages->nents,
+                              PCI_DMA_BIDIRECTIONAL))
+                       return 0;
+
+               /* If the DMA remap fails, one cause can be that we have
+                * too many objects pinned in a small remapping table,
+                * such as swiotlb. Incrementally purge all other objects and
+                * try again - if there are no more pages to remove from
+                * the DMA remapper, i915_gem_shrink will return 0.
+                */
+               GEM_BUG_ON(obj->mm.pages == pages);
+       } while (i915_gem_shrink(to_i915(obj->base.dev),
+                                obj->base.size >> PAGE_SHIFT,
+                                I915_SHRINK_BOUND |
+                                I915_SHRINK_UNBOUND |
+                                I915_SHRINK_ACTIVE));
 
        return -ENOSPC;
 }