From 2Q09 QSR on 6/30/09:
We have made significant progress on Xen sensor virtualization. Our recently submitted work demonstrates the
virtualization and slivering of a pan-tilt-zoom video camera within the Xen device driver framework. In this case,
slivering involves interleaving camera actuations at a fine-grain between multiple VMs. This quarter we began to
look at virtualizing ViSE radars in the same way. One difficulty that arose is that unlike the pan-tilt-zoom camera,
the device driver for the Analog-to-Digital card that connects to the radar does not work by default in domain-0
of Xen (i.e., the host VM). The reason is that the Analog-to-Digital card makes heavy use of DMA (since it transfers
substantial amounts of data), which domain-0 does not directly support. We are currently porting the driver
to work with Xen, but this requires significants changes to the driver and, potentially, to Xen itself. Others in the
Xen community are also looking similar problems related to DMA and PCI devices.
As a result, to meet this Spiral 1 milestone we are transitioning to using VServers, while we work through these
problems. VServers are a less powerful, but more robust, virtualization technology in wide use. For instance, PlanetLab
uses them exclusively. ViSE users, which primarily use the sensor’s on each node, should not be affected by
the change. We have chosen to use VServers while we work through the ADC issues with Xen because VServers
allow direct access to device files from VMs, while also allowing dynamic allocation and revocation of (sensing)
devices. These are pre-requisites for integrating a device with GENI. Since VServers virtualize at the OS-level,
the standard device drivers for the radar’s analog-to-digital card work out-of-the-box. One side-benefit of using
VServers while we work through the issues with Xen is that we will develop VServer resource handlers for Orca
that other groups will be able to use (if they desire). With the use of VServers we are on-track to complete this
milestone by August 1st, 2009, as scheduled. Once Xen support becomes available we should be able to switch
back to using Xen easily.
