Comment 36 for bug 604335

from qemu git:

commit 2930b313dd602d67a568815b0b031b824916cec9
Author: john cooper
Date: Fri Jul 2 13:44:25 2010 -0400

    Add virtio disk identification support

    This patch adds the final missing bits for support of
    passing a serial/id string to a virtio-blk guest driver.

    The guest-side component already exists in the virtio
    driver, and has recently been reworked by Ryan to export
    a /sys interface for retrieval of the id from guest userland.

    Signed-off-by: john cooper
    Signed-off-by: Kevin Wolf