[libvirt] Channel with virtio problem

I have configured the kvm and edit the xml as below, however there are an error when I want to run the guest.  The error as follows: virsh create libvirt.xml error: Failed to create domain from libvirt-test.xml error: XML description for unknown target type for character device: virtio is not well formed or invalid Please help me to solve this problem. ############################################################ <domain type='kvm'>     <name>i-5E36098H</name>     <os>     <type>hvm</type>           <kernel>/opt/eucalyptus-data/suria/i-5E36098H/kernel</kernel>         <initrd>/opt/eucalyptus-data/suria/i-5E36098H/ramdisk</initrd>  <cmdline>root=LABEL=root console=ttyS0</cmdline>     </os>     <features>         <acpi/>     </features>     <memory>13107200</memory>     <vcpu>1</vcpu>     <devices>         <emulator>/usr/bin/kvm</emulator>         <disk type='file'>             <source file='/opt/eucalyptus-data/suria/i-5E36098H/disk'/>             <target dev='vda' bus='virtio'/>         </disk>         <interface type='network'>             <source network='default'/>             <mac address='d0:0d:45:D2:08:01'/>             <model type='virtio'/>         </interface>         <controller type='ide' index='0'/>                 <controller type='virtio-serial' index='0' ports='16' vectors='4'/>                 <controller type='virtio-serial' index='1'>                 <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/>         </controller>         <parallel type='pty'>                 <source path='/dev/pts/2'/>                 <target port='0'/>         </parallel>         <serial type='pty'>                 <source path='/dev/pts/3'/>                 <!-- <source mode='bind' path='/var/lib/libvirt/qemu/va-i-5E36098H-isa.sock'/>-->                 <target type='virtio' port='0'/>         </serial>         <console type='pty'>                 <source path='/dev/pts/4'/>                 <target type='virtio' port='0'/>         </console>         <channel type='pty'>                 <source mode='bind' path='/var/lib/libvirt/qemu/va-i5E36098H-virtio.sock'/>                 <target type='virtio' name='org.qemu.guest_agent.0'/>                 <address type='virtio-serial' controller='0' bus='0' port='0'/>         </channel>          <graphics type='vnc' port='-1' autoport='yes' keymap='en-us'/>     </devices> ########################################################################