On Tue, Aug 16, 2011 at 03:46:23PM -0700, Daniel P. Berrange wrote: > On Tue, Aug 16, 2011 at 05:46:43PM -0400, Dave Allan wrote: > > On Tue, Aug 16, 2011 at 10:55:32PM +0200, Jiri Denemark wrote: > > > On Mon, Aug 08, 2011 at 13:48:59 +0200, Jiri Denemark wrote: > > > > 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. > > > > > > There have been no comments on this so far. Perhaps the topic is not so > > > controversial as I thought it was. But more likely it's just that people > > > are > > > busy with other things. IIRC, Daniel used to have a strong opinion on this > > > matter, is that right? > > > > I'm thinking that this boils down essentially to syntactic sugar. > > > > Would it not be possible to create a <cpu>host</cpu> that simply > > automates the process of copying the host capabilities into the > > running guest XML? That would allow libvirt to do pre-migration > > validation that the destination host was suitable, but also permit > > users to specify one value of <cpu> that should in theory run with the > > maximum capabilities of the particular host where the domain was > > started and not have to go through the work of copying the host > > capabilities every time before booting the guest. > > The goal of the XML is that it should always reflect the canonical > configuration of the guest. So when the guest is running it should > not show 'host' as the CPU model, but rather the real CPU model that > the guest is using. Although libvirt has the info internally, we want > that to be equally visible via the XML description to the app.
Agreed. Dave > Regards, > 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 :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
