Device iotlb
From KVM
Vhost-net Device IOTLB
Overview
This page provides information about the design of Device IOTLB for vhost-net to provides a secure and efficient environment for dpdk like program in guest.
Design Goals
- Architecture independent: The implementation should be compatible to current Qemu's IOMMU architecture, then it should be architecture independent and then be easy to be ported to various platform/IOMMU implementation.
- Efficient for dpdk like program: End user should have no obvious felling performance degradation when using dpdk like program in guest. The design was optimized for dpdk like programs which use fixed mappings in guest.
- Compatible: The implementation should be compatible to current vhost-net memory region API to support VM without DMAR enabled.
Design
- Vhost-net can query the address mappings from guest io virtual address to host virtual address through ioctl.
- The above translation result could be cached in a vhost device specific IOTLB for a while to speed up the future translation in the future.
- Qemu can invalidate one or more mappings that cached by vhost through ioctl.
- Qemu can start or stop the DMAR through ioctl.
Example
