Description of problem:

I'm trying to convert the following XM configuration, which works fine with Xen 3.2.1:

kernel      = '/boot/vmlinuz-2.6.26-2-xen-amd64'
ramdisk     = '/boot/initrd.img-2.6.26-2-xen-amd64'
memory      = '128'
root        = '/dev/xvda2 ro'
disk        = [
                  'file:/opt/xen/domains/domU/swap.img,xvda1,w',
                  'file:/opt/xen/domains/domU/disk.img,xvda2,w',
              ]
name        = 'domU'
dhcp        = 'dhcp'
vif = [ 'mac=00:16:3E:70:61:00,bridge=xenbr0' ]
on_poweroff = 'destroy'
on_reboot   = 'restart'
on_crash    = 'restart'

Version-Release number of selected component (if applicable):

0.8.0

How reproducible:

Steps to Reproduce:
1. Copy the above configuration to domU.cfg
2. Run: virsh domxml-from-native xen-xm domU.cfg
  
Actual results:

virsh prints:
error: Unknown failure

Expected results:

A libvirt domain XML 

Additional info:

By tracing the code I found that this can be avoided by adding a uuid field in the XM configuration file.
In this case, the XML produced is the following:

<domain type='xen'>
  <name>domU</name>
  <uuid>1e164e3e-880f-2b9f-4247-3d1f0ec6399a</uuid>
  <memory>131072</memory>
  <currentMemory>131072</currentMemory>
  <vcpu>1</vcpu>
  <os>
    <type arch='x86_64' machine='xenpv'>linux</type>
    <kernel>/boot/vmlinuz-2.6.26-2-xen-amd64</kernel>
    <initrd>/boot/initrd.img-2.6.26-2-xen-amd64</initrd>
  </os>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <disk type='file' device='disk'>
      <driver name='file'/>
      <source file='/opt/xen/domains/domU/swap.img'/>
      <target dev='xvda1' bus='xen'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='file'/>
      <source file='/opt/xen/domains/domU/disk.img'/>
      <target dev='xvda2' bus='xen'/>
    </disk>
    <interface type='bridge'>
      <mac address='00:16:3e:70:61:00'/>
      <source bridge='xenbr0'/>
    </interface>
    <console type='pty'>
      <target port='0'/>
    </console>
  </devices>
</domain>

However, this is still unusable since it is missing the "root" information from the XM file. I need to add the following for the VM to boot successfully:
<cmdline>root=/dev/xvda2 ro</cmdline>