Open Source Summit + Embedded Linux Conference Europe 2020

Direct assignment of I/O devices requires the host to statically pin the entire guest memory, thus hindering the efficiency of memory management. Presenting a vIOMMU can fix this but suffers from non-negligible cost of emulating the guest DMA remapping operations. Yu proposes a new vIOMMU architecture with a cooperative DMA buffer tracking mechanism, which is dedicated to achieving fine-grained pinning and is orthogonal to the costly DMA remapping interface. The new mechanism minimizes the VM-exits when enabling host/guest to coordinate the mapping/pinning requirement of active DMA buffers. It is designed in a vendor-agnostic way, thus can be applied to either emulated or para-virtualized vIOMMUs, Paper of this idea was accepted by USENIX ATC’20. In this talk, Yu'd like to talk more about the design/implementation challenges in KVM/Qemu, current status and upstreaming plan.