LA-vIOMMU: An Efficient Hardware-Software Co-design of IOMMU Virtualization

I/O Memory Management Unit (IOMMU) is important hardware support for I/O virtualization, and it is widely used in device passthrough. However, IOMMU sacrifices memory utilization due to the static mapping requirement. Moreover, it lacks DMA security guarantees inside the guest. IOMMU virtualization is a decent solution among existing studies to address these problems. Nevertheless, pure software IOMMU virtualization suffers from high overhead, while hardware-assisted IOMMU virtualization needs complex hardware redesign. Therefore, enabling efficient design with low hardware overhead remains challenging. In this paper, we propose an efficient hardware-software co-design of IOMMU virtualization, named LA-vIOMMU, to achieve high I/O performance with low hardware overhead. LA-vIOMMU is designed based on the existing vIOMMU mode and can be adapted to other platforms. We describe the design and implementation of LA-vIOMMU. The LA-vIOMMU combines hardware expansion and software optimization to minimize the performance cost. Furthermore, we evaluate the effectiveness and security of LA-vIOMMU and analyze the advantages compared with the existing design in x86. The experiment results show that LA-vIOMMU can get superior throughput than existing software approaches and achieve throughput pretty close to hardware-assisted virtualization with fewer hardware design changes and less verification overhead.