Comment 6 for bug 741706

Confirmed on 12.04. Enabled IOMMU, now virt-manager complains:

Error starting domain: internal error Process exited while reading console log output: char device redirected to /dev/pts/2
Failed to assign device "hostdev0" : Operation not permitted
kvm: -device pci-assign,host=02:00.0,id=hostdev0,configfd=20,bus=pci.0,addr=0x6: Device 'pci-assign' could not be initialized

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 45, in cb_wrapper
    callback(asyncjob, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 66, in tmpcb
    callback(*args, **kwargs)
  File "/usr/share/virt-manager/virtManager/domain.py", line 1120, in startup
    self._backend.create()
  File "/usr/lib/python2.7/dist-packages/libvirt.py", line 551, in create
    if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirtError: internal error Process exited while reading console log output: char device redirected to /dev/pts/2
Failed to assign device "hostdev0" : Operation not permitted
kvm: -device pci-assign,host=02:00.0,id=hostdev0,configfd=20,bus=pci.0,addr=0x6: Device 'pci-assign' could not be initialized

On a side node, virt-manager should most likely be modified to disable/grey out certain features if IOMMU is disabled.