drm/i915: Don't unconditionally try to deref aliasing ppgtt

Since the beginning, the functions which try to properly reference the
aliasing PPGTT have deferences a potentially null aliasing_ppgtt member.
Since the accessors are meant to be global, this will not do.

Introduced originally in:
commit a70a3148b0c61cb7c588ea650db785b261b378a3
Author: Ben Widawsky <ben@bwidawsk.net>
Date:   Wed Jul 31 16:59:56 2013 -0700

    drm/i915: Make proper functions for VMs

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 92149bcabe9839c6825407d69534dd6a581c076d..1f89a076e4f53ee72c362a6e556889e150794569 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4975,7 +4975,8 @@ unsigned long i915_gem_obj_offset(struct drm_i915_gem_object *o,
        struct drm_i915_private *dev_priv = o->base.dev->dev_private;
        struct i915_vma *vma;
 
-       if (vm == &dev_priv->mm.aliasing_ppgtt->base)
+       if (!dev_priv->mm.aliasing_ppgtt ||
+           vm == &dev_priv->mm.aliasing_ppgtt->base)
                vm = &dev_priv->gtt.base;
 
        BUG_ON(list_empty(&o->vma_list));
@@ -5016,7 +5017,8 @@ unsigned long i915_gem_obj_size(struct drm_i915_gem_object *o,
        struct drm_i915_private *dev_priv = o->base.dev->dev_private;
        struct i915_vma *vma;
 
-       if (vm == &dev_priv->mm.aliasing_ppgtt->base)
+       if (!dev_priv->mm.aliasing_ppgtt ||
+           vm == &dev_priv->mm.aliasing_ppgtt->base)
                vm = &dev_priv->gtt.base;
 
        BUG_ON(list_empty(&o->vma_list));