Comment 19 for bug 929545

This doesn't change what the VM boots from - we still require that the system boot from an IDE disk. What this does enable is our hv_storvsc driver to control the root device, which uses hv_vmbus to communicate with dom0. hv_storvsc and hv_blkvsc were merged upstream a while back, and hv_storvsc is a generic block device that handles both IDE and SCSI traffic.