Re: [libvirt] [RFC] Host CPU passthrough

Hi, AFAIK this topic is not new but I think we still do not have a good solution for it. Libvirt already supports specifying what CPU and its features a guest should see but imagine one wants to run a guest on the best possible CPU. The current way is to copy the <cpu> element from capabilities XML into domain XML. This approach is fine since it provides reproducible environment and such domain can even be migrated to a different host. But the CPU shown provided to a guest is not the same as the real host CPU. It's based on a model which doesn't reflect all aspects of real CPUs. Ideally, we would model everything but that's quite complicated and may need updating anytime a new CPU is introduced.