The xf86-video-qxl 0.0.13 driver begins hooking in UXA acceleration, the EXA-derived GEM-based acceleration architecture conceived by Intel for their driver. This QXL driver update also has a faster memory allocation (malloc) implementation, better debugging support code, and a number of bug fixes.
As UXA, the UMA Acceleration Architecture, isn't integrated into the mainline X.Org Server, the xf86-video-qxl driver adds its own copy of the UXA files to the driver, which tacks on around 6,400 lines of replicated code. This acceleration architecture was originally introduced by Intel in mid-2008 after they abandoned plans to advance EXA so they kept the EXA API while gutting it internally to hook into their Graphics Execution Manager API for pixmap memory management, etc. The Radeon and Nouveau drivers continue to use EXA for their 2D acceleration architecture.
The xf86-video-qxl 0.0.13 driver release announcement with a full list of changes can be found on the mailing list.