drm/i915/gem: Single page objects are naturally contiguous

Small objects that only occupy a single page are naturally contiguous,
so mark them as such and allow them the special abilities that come with
it.

A more thorough treatment would extend i915_gem_object_pin_map() to
support discontiguous lmem objects, following the example of
ioremap_prot() and use get_vm_area() + remap_io_sg().
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200101220736.1073007-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gem/i915_gem_region.c

@@ -107,7 +107,10 @@ void i915_gem_object_init_memory_region(struct drm_i915_gem_object *obj,
 {
 	INIT_LIST_HEAD(&obj->mm.blocks);
 	obj->mm.region = intel_memory_region_get(mem);
+
 	obj->flags |= flags;
+	if (obj->base.size <= mem->min_page_size)
+		obj->flags |= I915_BO_ALLOC_CONTIGUOUS;
 
 	mutex_lock(&mem->objects.lock);