Some files under /sys/bus/usb/devices/ have the format 'usbX', where
X is the USB bus number. Libvirt doesn't properly parse these files when trying to resolve produce/vendor to bus/device info. When it can't parse, the guest won't start. See also Fedora bug https://bugzilla.redhat.com/show_bug.cgi?id=598272
Fixed upstream here, should be a simple backport:
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release. Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release. This request is not yet committed for
Created attachment 426927 [details]
Backport of upstream fix
libvirt-0_8_1-11_el6 has been built in RHEL-6-candidate with the fix.
Verified PASSED with libvirt-0.8.1-13.el6.
VM start successfully with the following line in xml.
# virsh dumpxml demo
<hostdev mode='subsystem' type='usb' managed='yes'>
<address bus='1' device='1'/>
Red Hat Enterprise Linux 6.0 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.