Protection strategies for direct access to virtualized I/O devices

摘要: Commodity virtual machine monitors forbid direct access to I/O devices by untrusted guest operating systems in order provide protection and sharing. However, both memory management units (IOMMUs) recently proposed software-based methods can be used reduce the overhead of virtualization providing with safe, devices. This paper explores performance safety tradeoffs strategies for using these mechanisms. The presented this equivalent inter-guest among system instances. they varying levels intra-guest from driver software incur overhead. A simple direct-map strategy incurs least overhead, native-level but offering no enhanced misbehaving device drivers within system. Additional against achieved limiting IOMMU page-table mappings buffers that are actually transfers. Furthermore, cost incurred limitation minimized aggressively reusing mappings. Surprisingly, a software-only does not use an at all performs competitively, sometimes better than, hardware-based while maintaining strict isolation.