To provide various intelligent services in Internet of Vehicles (IoVs), such as autonomous driving, data sharing technologies enable vehicles to overcome information barriers and provide a big data foundation. Federated Learning (FL), which shares models instead of raw data, has emerged as a popular solution to address privacy concerns. However, current approaches are limited scalability and security, which are not suitable for the dynamic network topology of IoV scenarios. In this letter, we propose a Multi-Region Asynchronous Swarm Learning (MASL) framework in IoVs, which is empowered by the hierarchical blockchain and executed parallel between multiple regions. The MASL integrates identity verification and asynchronous model training while ensuring secure aggregation as well as data privacy. Through intra-regional and cross-regional sharing, the security and efficiency during large-scale data sharing in IoVs are effectively improved while alleviating the Non-IID data problem. Finally, both the simulation and hardware testbed results demonstrate that the proposed MASL framework could achieve better performances in terms of efficiency and security compared with the existing algorithms.