Nova's libvirt driver now allows the specification of granular CPU feature flags when configuring CPU models.
One benefit of this change is the alleviation of a performance degradation that has been experienced on guests running with certain Intel-based virtual CPU models after application of the "Meltdown" CVE fixes. This guest performance impact is reduced by exposing the CPU feature flag 'PCID' ("Process-Context ID") to the *guest* CPU, assuming that the PCID flag is available in the physical hardware itself.
For more details, refer to the documentation of ``[libvirt]/cpu_model_extra_flags`` in the ``nova.conf`` file for usage details.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.