vIOMMU: efficient IOMMU emulation

摘要: Direct device assignment, where a guest virtual machine directly interacts with an I/O without host intervention, is appealing, because it allows unmodified (non-hypervisor-aware) to achieve near-native performance. But assignment for guests suffers from two serious deficiencies: (1) requires pinning all of the guest's pages, thereby disallowing memory overcommitment, and (2) exposes buggy drivers. We solve these problems by designing, implementing, exposing emulated IOMMU (vIOMMU) guest. We employ novel optimizations make vIOMMU perform well: waiting few milliseconds before tearing down mapping in hope will be immediately reused ("optimistic teardown"), running on sidecore, enabling first time use sidecore guests. Both are highly effective isolation. The former bare-metal 100% 10Gbps line rate. combination do same.