libvirt users - Nov 2012 - How to passthru a block device from host to the quest os in kvm?

Hi,

Is there any APIs or some XML scheme can passthru a local block device 
of the host, eg, /dev/sda1 to its running guest OS?
Specifically, say there is a block device /dev/sda1 in the host, mount 
it: mount /dev/sda1 /mnt; ls /mnt:
a.file, b.file

After passthru, the same /dev/sda1 can be used by the quest os(maybe the 
dev name is changed): mount /dev/sda1 /mnt; ls /mnt:
a.file, b.file.

BRs,
Dennis