From KVM
(Vhost-net Device IOTLB)
(Design Goals)
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*  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.
 
*  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.
+
* 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.
 
* Compatible: The implementation should be compatible to current vhost-net memory region API to support VM without DMAR enabled.
  

Revision as of 09:10, 4 February 2016

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

Iotlb.png