[libvirt-users] Help!

Buddy, I am a noob in libvirt develop. When I want to create a domain by using virDomainDefineXML and displays a window on the host desktop. But when I add the line " <graphics type='sdl' display=':0.0'/>" into the config xml file, the error as below will happen. libvir: QEMU error : internal error process exited while connecting to monitor: Could not initialize SDL(No available video device) - exiting when I delete " <graphics type='sdl' display=':0.0'/>",I can create the domain normally. Who can help me?! The config xml file is as below: <domain type='qemu'> <name>qemu_ubuntu_01</name> <memory>219200</memory> <currentMemory>219200</currentMemory> <vcpu>2</vcpu> <os> <type arch='x86_64' machine='pc'>hvm</type> <boot dev='hd'/> <boot dev='cdrom'/> </os> <devices> <emulator>/usr/bin/qemu</emulator> <disk type='file' device='cdrom'> <source file='/root/Downloads/ubuntu-11.04-desktop-amd64.iso'/> <target dev='hdc' bus='ide'/> <readonly/> </disk> <disk type='file' device='disk'> <source file='/var/lib/libvirt/images/winXP.img'/> <driver name='qemu' type='raw'/> <target dev='hda'/> </disk> <video> <model type='cirrus' vram='9216' heads='1'> <acceleration accel3d='yes'/> </model> </video> <interface type='bridge'> <mac address='52:54:00:d8:65:c9'/> <source bridge='virbr0'/> </interface> <input type='mouse' bus='ps2'/> <graphics type='vnc' port='10' listen='127.0.0.1'/> <graphics type='sdl' display=':0.0'/> </devices> </domain>