i want add sound card to domain xml when guest start,after google,i found libvirt provide hook function.

i follow the instruction to make a python,and boot a guest,but after use "virsh edit" its still dont have sound card config

/etc/libvirt/hooks/qemu:

#!/usr/bin/python

import sys

import re

import os

hooklog = '/tmp/hook.log'

log = open(hooklog, 'w')

stdinxml = sys.stdin.readlines()

if sys.argv[2] == 'start':

  log.write("hook start,domain name: %s \n" % sys.argv[1])

  maxslot=-1

  for line in stdinxml:

    slotm = re.search("slot='(?P<slotnum>0x[0-9a-fA-F]{2})'", line)

    if slotm:

      slotnum = int(slotm.group('slotnum'),0)

      if slotnum > maxslot:

        maxslot = slotnum

    if '</devices>' in line:

      log.write("insert sound card config \n")

      slotnum = maxslot + 1

      line = "    <sound model='ich6'>\n"

      line = line + "      <address type='pci' domain='0x0000' bus='0x00' slot='0x%0.2X' function='0x0'/>\n" % slotnum

      line = line + "    </sound>\n"

      line = line + "  </devices>\n"

    stdoutxml = ''.join(line)

    sys.stdout.write(stdoutxml)

tail -f /tmp/hook.log:

hook start,domain name: instance-00000222                              

insert sound card config                              

tail /var/log/libvirt/libvirtd.log:

2014-04-16 07:13:39.159+0000: 52199: warning : qemuDomainObjTaint:1377 : Domain id=81 name='instance-00000222' uuid=974d62b7-f316-4f20-a91c-d11cb85980fe is tainted: high-privileges                                                                       

in these log,hook script seems to executed,but not effective.

can anyone tell me where is wrong?