drm/i915/ttm: disallow CPU fallback mode for ccs pages

Falling back to memcpy/memset shouldn't be allowed if we know we have
CCS state to manage using the blitter. Otherwise we are potentially
leaving the aux CCS state in an unknown state, which smells like an info
leak.

Fixes: 48760ffe ("drm/i915/gt: Clear compress metadata for Flat-ccs objects")
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Kenneth Graunke <kenneth@whitecape.org>
Cc: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220629174350.384910-12-matthew.auld@intel.com

drivers/gpu/drm/i915/gem/i915_gem_object.c

@@ -717,6 +717,32 @@ bool i915_gem_object_placement_possible(struct drm_i915_gem_object *obj,
 	return false;
 }
 
+/**
+ * i915_gem_object_needs_ccs_pages - Check whether the object requires extra
+ * pages when placed in system-memory, in order to save and later restore the
+ * flat-CCS aux state when the object is moved between local-memory and
+ * system-memory
+ * @obj: Pointer to the object
+ *
+ * Return: True if the object needs extra ccs pages. False otherwise.
+ */
+bool i915_gem_object_needs_ccs_pages(struct drm_i915_gem_object *obj)
+{
+	bool lmem_placement = false;
+	int i;
+
+	for (i = 0; i < obj->mm.n_placements; i++) {
+		/* Compression is not allowed for the objects with smem placement */
+		if (obj->mm.placements[i]->type == INTEL_MEMORY_SYSTEM)
+			return false;
+		if (!lmem_placement &&
+		    obj->mm.placements[i]->type == INTEL_MEMORY_LOCAL)
+			lmem_placement = true;
+	}
+
+	return lmem_placement;
+}
+
 void i915_gem_init__objects(struct drm_i915_private *i915)
 {
 	INIT_DELAYED_WORK(&i915->mm.free_work, __i915_gem_free_work);

drivers/gpu/drm/i915/gem/i915_gem_object.h

@@ -618,6 +618,8 @@ int i915_gem_object_wait_migration(struct drm_i915_gem_object *obj,
 bool i915_gem_object_placement_possible(struct drm_i915_gem_object *obj,
 					enum intel_memory_type type);
 
+bool i915_gem_object_needs_ccs_pages(struct drm_i915_gem_object *obj);
+
 int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st,
 			 size_t size, struct intel_memory_region *mr,
 			 struct address_space *mapping,

drivers/gpu/drm/i915/gem/i915_gem_ttm.c

@@ -266,24 +266,6 @@ static const struct i915_refct_sgt_ops tt_rsgt_ops = {
 	.release = i915_ttm_tt_release
 };
 
-static inline bool
-i915_gem_object_needs_ccs_pages(struct drm_i915_gem_object *obj)
-{
-	bool lmem_placement = false;
-	int i;
-
-	for (i = 0; i < obj->mm.n_placements; i++) {
-		/* Compression is not allowed for the objects with smem placement */
-		if (obj->mm.placements[i]->type == INTEL_MEMORY_SYSTEM)
-			return false;
-		if (!lmem_placement &&
-		    obj->mm.placements[i]->type == INTEL_MEMORY_LOCAL)
-			lmem_placement = true;
-	}
-
-	return lmem_placement;
-}
-
 static struct ttm_tt *i915_ttm_tt_create(struct ttm_buffer_object *bo,
 					 uint32_t page_flags)
 {

drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c

@@ -435,6 +435,9 @@ i915_ttm_memcpy_work_arm(struct i915_ttm_memcpy_work *work,
 static bool i915_ttm_memcpy_allowed(struct ttm_buffer_object *bo,
 				    struct ttm_resource *dst_mem)
 {
+	if (i915_gem_object_needs_ccs_pages(i915_ttm_to_gem(bo)))
+		return false;
+
 	if (!(i915_ttm_resource_mappable(bo->resource) &&
 	      i915_ttm_resource_mappable(dst_mem)))
 		return false;