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

-----Original Message----- From: Daniel P. Berrange [mailto:berrange@redhat.com] Sent: Wednesday, November 14, 2012 6:45 PM To: Ichikawa, Ken/市川 顕 Cc: libvir-list(a)redhat.com; eblake(a)redhat.com; gaofeng(a)cn.fujitsu.com; Kaneshige, Kenji/金重 憲治 Subject: Re: [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.

Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|