CentOS virt - Jan 2016 - Disable ps2 mouse and keyboard in a kvm guest

Hi all,

  I have to do some tests with a kvm guest but I need to disable ps2 
mouse and ps2 keyboard and use only usb keyboard/mouse.

  When I try to remove them, virt-manager adds them automatically.

  How can I disable all ps2 devices? Any idea?

Thanks.