drm/i915/bdw: Free PPGTT struct

GEN8 never freed the PPGTT struct. As GEN8 doesn't use full PPGTT, the
leak is small and only found on a module reload. ie. I don't think this
needs to go to stable.

v2: The very naive, kfree in gen8 ppgtt cleanup, is subject to a double
free on PPGTT initialization failure. (Spotted by Imre). Instead this
patch pulls the ppgtt struct freeing out of the cleanup and leaves it to
the allocators/callers or the one doing the last kref_put as in standard
convention

Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_context.c

@@ -99,9 +99,8 @@
 static int do_switch(struct intel_ring_buffer *ring,
 		     struct i915_hw_context *to);
 
-static void ppgtt_release(struct kref *kref)
+static void do_ppgtt_cleanup(struct i915_hw_ppgtt *ppgtt)
 {
-	struct i915_hw_ppgtt *ppgtt = container_of(kref, struct i915_hw_ppgtt, ref);
 	struct drm_device *dev = ppgtt->base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct i915_address_space *vm = &ppgtt->base;
@@ -135,6 +134,15 @@ static void ppgtt_release(struct kref *kref)
 	ppgtt->base.cleanup(&ppgtt->base);
 }
 
+static void ppgtt_release(struct kref *kref)
+{
+	struct i915_hw_ppgtt *ppgtt =
+		container_of(kref, struct i915_hw_ppgtt, ref);
+
+	do_ppgtt_cleanup(ppgtt);
+	kfree(ppgtt);
+}
+
 static size_t get_context_alignment(struct drm_device *dev)
 {
 	if (IS_GEN6(dev))

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -859,7 +859,6 @@ static void gen6_ppgtt_cleanup(struct i915_address_space *vm)
 	for (i = 0; i < ppgtt->num_pd_entries; i++)
 		__free_page(ppgtt->pt_pages[i]);
 	kfree(ppgtt->pt_pages);
-	kfree(ppgtt);
 }
 
 static int gen6_ppgtt_init(struct i915_hw_ppgtt *ppgtt)