[Intel-gfx] [PATCH] drm/i915: Skip unbinding large unmappable global buffers

[Chris Wilson]

If the user requests a mappable binding to the global GTT, we will first
unbind an existing mapping if it doesn't match. We will unbind even if
there is no possibility that the object can fit in the mappable
aperture. This may lead to a ping-pong migration of the object, for
example igt/gem_exec_big.

Testcase: igt/gem_exec_big
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 2f939f90984b..f33aa9bb95c0 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3144,6 +3144,9 @@ search_free:
 
 			goto err_unpin;
 		}
+
+		GEM_BUG_ON(vma->node.start < start);
+		GEM_BUG_ON(vma->node.start + vma->node.size > end);
 	}
 	GEM_BUG_ON(!i915_gem_valid_gtt_space(vma, obj->cache_level));
 
@@ -3843,7 +3846,8 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
 			 u64 alignment,
 			 u64 flags)
 {
-	struct i915_address_space *vm = &to_i915(obj->base.dev)->ggtt.base;
+	struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
+	struct i915_address_space *vm = &dev_priv->ggtt.base;
 	struct i915_vma *vma;
 	int ret;
 
@@ -3858,6 +3862,19 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
 		    (i915_vma_is_pinned(vma) || i915_vma_is_active(vma)))
 			return ERR_PTR(-ENOSPC);
 
+		if (flags & PIN_MAPPABLE) {
+			u32 fence_size;
+
+			fence_size = i915_gem_get_ggtt_size(dev_priv, vma->size,
+							    i915_gem_object_get_tiling(obj));
+			if (fence_size > dev_priv->ggtt.mappable_end)
+				return ERR_PTR(-E2BIG);
+
+			if (flags & PIN_NONBLOCK &&
+			    fence_size > dev_priv->ggtt.mappable_end / 2)
+				return ERR_PTR(-ENOSPC);
+		}
+
 		WARN(i915_vma_is_pinned(vma),
 		     "bo is already pinned in ggtt with incorrect alignment:"
 		     " offset=%08x, req.alignment=%llx,"
-- 
2.9.3