As we now mark the reserved hole (drm_mm.head_node) with the special
UNEVICTABLE color, we can use the page coloring to avoid prefetching of
the CS beyond the end of the GTT.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_evict.c | 10 ++++++++--
drivers/gpu/drm/i915/i915_gem_gtt.c | 19 ++++++++++++-------
2 files changed, 20 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c
index c181b1bb3d2c..776c508cb9ae 100644
--- a/drivers/gpu/drm/i915/i915_gem_evict.c
+++ b/drivers/gpu/drm/i915/i915_gem_evict.c
@@ -258,6 +258,9 @@ int i915_gem_evict_for_node(struct i915_address_space *vm,
int ret = 0;
lockdep_assert_held(&vm->i915->drm.struct_mutex);
+ GEM_BUG_ON(!IS_ALIGNED(start, I915_GTT_PAGE_SIZE));
+ GEM_BUG_ON(!IS_ALIGNED(end, I915_GTT_PAGE_SIZE));
+
trace_i915_gem_evict_node(vm, target, flags);
/* Retire before we search the active list. Although we have
@@ -273,9 +276,11 @@ int i915_gem_evict_for_node(struct i915_address_space *vm,
/* Expand search to cover neighbouring guard pages (or lack!) */
if (start > vm->start)
start -= I915_GTT_PAGE_SIZE;
- if (end < vm->start + vm->total)
- end += I915_GTT_PAGE_SIZE;
+
+ /* Always look at the page afterwards to avoid the end-of-GTT */
+ end += I915_GTT_PAGE_SIZE;
}
+ GEM_BUG_ON(start >= end);
drm_mm_for_each_node_in_range(node, &vm->mm, start, end) {
/* If we find any non-objects (!vma), we cannot evict them */
@@ -284,6 +289,7 @@ int i915_gem_evict_for_node(struct i915_address_space *vm,
break;
}
+ GEM_BUG_ON(!node->allocated);
vma = container_of(node, typeof(*vma), node);
/* If we are using coloring to insert guard pages between
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 75cd2a56b8b4..959764394718 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -2718,11 +2718,16 @@ static void i915_gtt_color_adjust(const struct drm_mm_node *node,
u64 *start,
u64 *end)
{
- if (node->color != color)
+ if (node->allocated && node->color != color)
*start += I915_GTT_PAGE_SIZE;
+ /* Also leave a space between the unallocated reserved node after the
+ * GTT and any objects within the GTT, i.e. we use the color adjustment
+ * to insert a guard page to prevent prefetches crossing over the
+ * GTT boundary.
+ */
node = list_next_entry(node, node_list);
- if (node->allocated && node->color != color)
+ if (node->color != color)
*end -= I915_GTT_PAGE_SIZE;
}
@@ -3241,14 +3246,14 @@ int i915_ggtt_init_hw(struct drm_i915_private *dev_priv)
INIT_LIST_HEAD(&dev_priv->vm_list);
- /* Subtract the guard page before address space initialization to
- * shrink the range used by drm_mm.
+ /* Note that we use page colouring to enforce a guard page at the
+ * end of the address space. This is required as the CS may prefetch
+ * beyond the end of the batch buffer, across the page boundary,
+ * and beyond the end of the GTT if we do provide a guard.
*/
mutex_lock(&dev_priv->drm.struct_mutex);
- ggtt->base.total -= I915_GTT_PAGE_SIZE;
i915_address_space_init(&ggtt->base, dev_priv, "[global]");
- ggtt->base.total += I915_GTT_PAGE_SIZE;
- if (!HAS_LLC(dev_priv))
+ if (!HAS_LLC(dev_priv) && !USES_PPGTT(dev_priv))
ggtt->base.mm.color_adjust = i915_gtt_color_adjust;
mutex_unlock(&dev_priv->drm.struct_mutex);
--
2.11.0
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