---
features:
  - |
    The libvirt driver now allows specifying individual CPU feature
    flags for guest, via a new configuration parameter
    ``[libvirt]/cpu_model_extra_flags`` -- this is valid in combination
    with all the three possible values for ``[libvirt]/cpu_mode``:
    ``custom``, ``host-model`` and ``host-passthrough``. The
    ``cpu_model_extra_flags`` allows specifying multiple CPU flags.
    The recent "Meltdown" CVE fixes have resulted in critical
    performance penalty which impacts every Nova guest within
    certain CPU models.

    More info is available in `nova release notes <https://docs.openstack.org/releasenotes/nova/queens.html#bug-fixes>`_.