Re: [libvirt] [PATCH] qemu conf: Use host-model for cpu mode by default

On Wed, Nov 14, 2012 at 03:10:48AM +0000, Ichikawa, Ken wrote: > Now, qemu guest's default cpu model is qemu32/64 and it can be > configured per domain. In some case, host-model mode is suitable for > getting enough performance in the guest because of features from cpu > spec. > > This patch adds a config option to qemu.conf to use 'host-model' > mode as default and allow users to use host-model mode in domains on a host. > This is useful because > - Guest owners don't need to touch their domain's config. > - An administrator can reduce an item in their checklist for VM > performance and guarantee all guests should run in the best performance. While I understand the benefits, I'm afraid I have to NACK this at this time because using host-model doesn't really work when trying to use nested-KVM. Until we have a solution for that, we neeed to stick with a CPU model that works everywhere, since users like OpenStack do actually use nested-KVM for testing work and already complained about this when I made OpenStack set the host-model by default.