Notes about guest memory pinning when direct assignment of I/O devices

当pass-thru device时，Hypervisor会建立dma remapping，但是存在一个问题就是:it requires the hypervisor to statically pin the entire guest memory. 原因如下:

[ATC’11 vIOMMU: Efficient IOMMU Emulation]

http://awilliam.github.io/presentations/KVM-Forum-2016/#/2/19

优化的工作有:

1. ATC’11 vIOMMU: Efficient IOMMU Emulation
2. ATC’20 coIOMMU: A Virtual IOMMU with Cooperative DMA Buffer Tracking for Efficient Memory Management in Direct I/O