[Intel-gfx] [PATCH] drm/i915/gem: Poison stolen pages before use

[Chris Wilson]

When allocating objects from stolen, memset() the backing store to
POISON_INUSE (0x5a) to help identify any uninitialised use of a stolen
object.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gem/i915_gem_stolen.c | 33 ++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
index 0be5e8683337..4c2869c0a802 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
@@ -572,6 +572,38 @@ static const struct drm_i915_gem_object_ops i915_gem_object_stolen_ops = {
 	.release = i915_gem_object_release_stolen,
 };
 
+static void dbg_poison(struct drm_i915_gem_object *obj)
+{
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
+	struct drm_i915_private *i915 = to_i915(obj->base.dev);
+	struct i915_ggtt *ggtt = &i915->ggtt;
+	struct sgt_iter iter;
+	dma_addr_t addr;
+
+	if (!drm_mm_node_allocated(&ggtt->error_capture))
+		return;
+
+	mutex_lock(&ggtt->error_mutex);
+	for_each_sgt_daddr(addr, iter, obj->mm.pages) {
+		void __iomem *s;
+
+		ggtt->vm.insert_page(&ggtt->vm, addr,
+				     ggtt->error_capture.start,
+				     I915_CACHE_NONE, 0);
+		mb();
+
+		s = io_mapping_map_wc(&ggtt->iomap,
+				      ggtt->error_capture.start,
+				      PAGE_SIZE);
+		memset(s, POISON_INUSE, PAGE_SIZE);
+		io_mapping_unmap(s);
+	}
+	mb();
+	ggtt->vm.clear_range(&ggtt->vm, ggtt->error_capture.start, PAGE_SIZE);
+	mutex_unlock(&ggtt->error_mutex);
+#endif
+}
+
 static struct drm_i915_gem_object *
 __i915_gem_object_create_stolen(struct intel_memory_region *mem,
 				struct drm_mm_node *stolen)
@@ -598,6 +630,7 @@ __i915_gem_object_create_stolen(struct intel_memory_region *mem,
 		goto cleanup;
 
 	i915_gem_object_init_memory_region(obj, mem, 0);
+	dbg_poison(obj);
 
 	return obj;
 
-- 
2.20.1