CentOS virt - Feb 2012 - virt-io drivers for 64 bit Win7 needed for USB passthrough?

Have been trying to get a 64-bit Win7 guest to access a usb thumbdrive
(and eventually an Apple iTouch).  Host is CentOS 6.2 and the guest is
running under qemu-kvm with SELinux enabled and sVirt separating guests
from each other and guests from the host.

Do I need to install the virt-io drivers in the Win7 guest, or are there
more permission and SELinux blocks in my path?

Dave