I tried to create a qemu-kvm virtual machine on a remote libvirt server, and
selected to customize the system before starting the installation. There I
selected to copy the host processor features to the guest.

When creating the VM, it failed with this error:

Unable to complete install: 'unsupported configuration: host doesn't support
invariant TSC'

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 91, in
cb_wrapper
    callback(asyncjob, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/create.py", line 1787, in
do_install
    guest.start_install(meter=meter)
  File "/usr/share/virt-manager/virtinst/guest.py", line 403, in start_install
    noboot)
  File "/usr/share/virt-manager/virtinst/guest.py", line 467, in _create_guest
    dom = self.conn.createLinux(start_xml or final_xml, 0)
  File "/usr/lib/python2.7/dist-packages/libvirt.py", line 3440, in createLinux
    if ret is None:raise libvirtError('virDomainCreateLinux() failed',
conn=self)
libvirtError: unsupported configuration: host doesn't support invariant TSC

I found these bug reports with patches. If I understand this correctly, both
libvirt-bin, virt-daemon and virt-install need a patch to fix this:

https://bugzilla.redhat.com/show_bug.cgi?id=1133155
https://bugzilla.redhat.com/show_bug.cgi?id=1138221