Device iotlb

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: End user should have no obvious felling performance degradation when using dpdk like program 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 io virtual address to userspace address through ioctl.
• The above translation result could be cached in vhost 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.