[libvirt-users] hello, I 've deployed libvirt, and it is OK to use kvm.But when I use virtualbox, I can not attach a device to a domain

hello,I 've deployed libvirt, and it is OK to use kvm.But when I use virtualbox,I can not attach a device to a domain. It reports the error that can't get device from device.xml here is my xml file for device(device.xml): <disk type='block'> <driver name='phy'/> <source dev="/home/lb/iscsitest/vdisk.img"/> <target dev='sdb' bus='usb'/> </disk> and the xml file for the vm: <domain type='vbox'> <name>winxp_3D</name> <uuid>d2542bf2-3d56-41fa-a048-4f9a7ed3cf4a</uuid> <memory>787456</memory> <currentMemory>787456</currentMemory> <vcpu>1</vcpu> <os> <type arch='x86_64'>hvm</type> <boot dev='fd'/> <boot dev='cdrom'/> <boot dev='hd'/> </os> <features> <acpi/> </features> <clock offset='localtime'/> <on_poweroff>destroy</on_poweroff> <on_reboot>destroy</on_reboot> <on_crash>destroy</on_crash> <devices> <disk type='file' device='disk'> <source file='/root/VirtualBox VMs/winxp_3D/winxp_3D.vdi'/> <target dev='hda' bus='ide'/> </disk> <interface type='bridge'> <mac address='08:00:27:6f:c6:4f'/> <source bridge='tap0'/> <model type='Am79C973'/> </interface> <input type='mouse' bus='ps2'/> <graphics type='desktop' display=':0.0'/> <sound model='ac97'/> <video> <model type='vbox' vram='32768' heads='1'> <acceleration accel3d='yes' accel2d='yes'/> </model> </video> </devices> </domain>