drm/i915/bdw: Don't muck with gtt_size on Gen8 when PPGTT setup fails

v2: Resolve rebase conflicts and switch to gen < 8 color for GenX
checking.

v3: Rebase on top of the address space refactoring.
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (v1)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -1182,7 +1182,8 @@ void i915_gem_init_global_gtt(struct drm_device *dev)
 
 		DRM_ERROR("Aliased PPGTT setup failed %d\n", ret);
 		drm_mm_takedown(&dev_priv->gtt.base.mm);
-		gtt_size += GEN6_PPGTT_PD_ENTRIES * PAGE_SIZE;
+		if (INTEL_INFO(dev)->gen < 8)
+			gtt_size += GEN6_PPGTT_PD_ENTRIES*PAGE_SIZE;
 	}
 	i915_gem_setup_global_gtt(dev, 0, mappable_size, gtt_size);
 }