In the vehicular mixed reality (MR) Metaverse, the distance between physical
and virtual entities can be overcome by fusing the physical and virtual
environments with multi-dimensional communications in autonomous driving
systems. Assisted by digital twin (DT) technologies, connected autonomous
vehicles (AVs), roadside units (RSU), and virtual simulators can maintain the
vehicular MR Metaverse via digital simulations for sharing data and making
driving decisions collaboratively. However, large-scale traffic and driving
simulation via realistic data collection and fusion from the physical world for
online prediction and offline training in autonomous driving systems are
difficult and costly. In this paper, we propose an autonomous driving
architecture, where generative AI is leveraged to synthesize unlimited
conditioned traffic and driving data in simulations for improving driving
safety and traffic efficiency. First, we propose a multi-task DT offloading
model for the reliable execution of heterogeneous DT tasks with different
requirements at RSUs. Then, based on the preferences of AV's DTs and collected
realistic data, virtual simulators can synthesize unlimited conditioned driving
and traffic datasets to further improve robustness. Finally, we propose a
multi-task enhanced auction-based mechanism to provide fine-grained incentives
for RSUs in providing resources for autonomous driving. The property analysis
and experimental results demonstrate that the proposed mechanism and
architecture are strategy-proof and effective, respectively