drm/i915: Handle i915_ppgtt_put correctly

Unfortunately, the gem_obj/vma relationship is not symmetrical; a gem_obj
can look up for the same vma more than once (where the ppgtt refcount is
incremented), but will free the vma only once (i915_gem_free_object).

This difference in refcount get/put means that the ppgtt is not removed
after the context and vma are destroyed, because sometimes the refcount
will never go back to zero.

v2: Just move the ppgtt refcount into vma_create.

OTC-Jira: VIZ-3719
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -2141,8 +2141,10 @@ static struct i915_vma *__i915_gem_vma_create(struct drm_i915_gem_object *obj,
 	/* Keep GGTT vmas first to make debug easier */
 	if (i915_is_ggtt(vm))
 		list_add(&vma->vma_link, &obj->vma_list);
-	else
+	else {
 		list_add_tail(&vma->vma_link, &obj->vma_list);
+		i915_ppgtt_get(i915_vm_to_ppgtt(vm));
+	}
 
 	return vma;
 }
@@ -2157,8 +2159,5 @@ i915_gem_obj_lookup_or_create_vma(struct drm_i915_gem_object *obj,
 	if (!vma)
 		vma = __i915_gem_vma_create(obj, vm);
 
-	if (!i915_is_ggtt(vm))
-		i915_ppgtt_get(i915_vm_to_ppgtt(vm));
-
 	return vma;
 }