Virtualbricks e Virtual Machine Manager bugados no Debian 9

ão foi possível completar a instalação: "unsupported configuration: CPU mode 'custom' for x86_64 kvm domain on x86_64 host is not supported by hypervisor"

Traceback (most recent call last):
File "/usr/share/virt-manager/virtManager/asyncjob.py", line 88, in cb_wrapper
callback(asyncjob, *args, **kwargs)
File "/usr/share/virt-manager/virtManager/create.py", line 2288, in _do_async_install
guest.start_install(meter=meter)
File "/usr/share/virt-manager/virtinst/guest.py", line 461, in start_install
doboot, transient)
File "/usr/share/virt-manager/virtinst/guest.py", line 396, in _create_guest
self.domain = self.conn.createXML(install_xml or final_xml, 0)
File "/usr/lib/python2.7/dist-packages/libvirt.py", line 3523, in createXML
if ret is None:raise libvirtError('virDomainCreateXML() failed', conn=self)
libvirtError: unsupported configuration: CPU mode 'custom' for x86_64 kvm domain on x86_64 host is not supported by hypervisor