Live Migration with Pass-through Device for Linux VM

Open source Linux virtualization, such as Xen and KVM, has made great progress recently, and has been a hot topic in Linux world for years. With virtualization support, the hypervisor de-privileges operating systems as guest operating systems and shares physical resources among guests, such as memory and the network device. For device virtualization, some mechanisms are introduced for improving performance. Paravirtualized (PV) drivers are implemented to avoid excessive guest and hypervisor switching and thus achieve better performance, for example Xen’s split virtual network interface driver (VNIF). Unlike software optimization in PV driver, IOMMU, such as Intel R © Virtualization Technology for Directed I/O, AKA VT-d, enables direct passing through of physical devices to guests to take advantage of hardware DMA remapping, thus reducing hypervisor intervention and achieving high bandwidth. Physically assigned devices impose challenges to live migration, which is one of the most important virtualization features in server consolidation. This paper shows how we solve this issue using virtual hot plug technology, in addition with the Linux bonding driver, and is organized as follows: We start from device virtualization and live migration challenges, followed by the design and implementation of the virtual hotplug based solution. The network connectivity issue is also addressed using the bonding driver for live migration with a direct assigned NIC device. Finally, we present the current status, future work, and other alternative solutions.