drm/i915: Do not allow buffers at offset 0

This is primarily a band aid for an unexplainable error in
gem_reloc_vs_gpu/forked-faulting-reloc-thrashing. Essentially as soon as
a relocated buffer (which had a non-zero presumed offset) moved to
offset 0, something goes bad. Since I have been unable to solve this,
and potentially this is a good thing to do anyway, since many things can
accidentally write to offset 0, why not?

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 99c05e3cf4190361273989ac23d5bbf0cbd79f01..0572257ac6f6b16c5a436ccdef46bfb8989d1475 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3280,9 +3280,11 @@ i915_gem_object_bind_to_vm(struct drm_i915_gem_object *obj,
        WARN_ON(!list_is_singular(&obj->vma_list));
 
 search_free:
+       /* FIXME: Some tests are failing when they receive a reloc of 0. To
+        * prevent this, we simply don't allow the 0th offset. */
        ret = drm_mm_insert_node_in_range_generic(&vm->mm, &vma->node,
                                                  size, alignment,
-                                                 obj->cache_level, 0, gtt_max,
+                                                 obj->cache_level, 1, gtt_max,
                                                  DRM_MM_SEARCH_DEFAULT);
        if (ret) {
                ret = i915_gem_evict_something(dev, vm, size, alignment,