Live migration of direct-access devices

  • Authors:

  • Asim Kadav;Michael M. Swift

  • Affiliations:

  • Computer Sciences Department, University of Wisconsin-Madison;Computer Sciences Department, University of Wisconsin-Madison

  • Venue:
  • WIOV'08 Proceedings of the First conference on I/O virtualization
  • Year:
  • 2008

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Abstract

Virtual machine migration greatly aids management by allowing flexible provisioning of resources and decommissioning of hardware for maintenance. However, efforts to improve network performance by granting virtual machines direct access to hardware currently prevent migration. This occurs because (1) the VMM cannot migrate the state of the device, and (2) the source and destination machines may have different network devices, requiring different drivers to run in the migrated virtual machine. In this paper, we describe a lightweight software mechanism for migrating virtual machines with direct hardware access. We base our solution on shadow drivers, which efficiently capture and reset the state of a device driver. On the source hardware, the shadow driver continuously monitors the state of the driver and device. After migration, the shadow driver uses this information to configure a driver for the corresponding device on the destination. We implement our solution for Linux network drivers running on the Xen hypervisor. We show that the performance overhead, compared to direct hard-ware access, is negligible and is much better than using a virtual NIC.