Hi, With the meltdown patches, now it is specially beneficial to have the pcid feature in the virtual CPUs. See: https://groups.google.com/forum/#!topic/mechanical-sympathy/L9mHTbeQLNU The PCID feature is available in physical "Westmere" (Release date circa 2010) or newer CPUs. However, in libvirt the pcid feature is only avalilable for virtual CPUs Haswell (Release date circa 2013) or newer. The recomendation is using Haswell, Broadwell or Skylake based model or host passthrough. Now, I think "host passthrough" is not an option for oVirt for good reason so this leaves Haswell, Broadwell or Skylake as options. Is it possible to edit /usr/share/libvirt/cpu_map.xml on the compute nodes to add the pcid feature to the virtual CPU models between Westmere and Haswell (that would be Westmere and SandyBridge)? Is anyone aware if something like this is being considered by the libvirt developers? Actually understanding the implications or doing so is way beyond my skill level. By now you may have guessed that my oVirt clusters use physical Westmere and SandyBridge CPUs :-/ Thanks in advance for your help! -- Eduardo Mayoral Jimeno (emayoral@arsys.es) Administrador de sistemas. Departamento de Plataformas. Arsys internet. +34 941 620 145 ext. 5153