Re: [libvirt] domain XML for tracking libosinfo ID

On Wed, Sep 05, 2018 at 03:37:22PM +0100, Daniel P. Berrangé wrote: > On Wed, Sep 05, 2018 at 02:01:42PM +0200, Martin Kletzander wrote: >> On Wed, Sep 05, 2018 at 09:28:52AM +0100, Daniel P. Berrangé wrote: >> > On Tue, Sep 04, 2018 at 03:44:12PM -0400, Cole Robinson wrote: >> > > Right now in virt-manager we only track a VM's OS name (win10, >> fedora28, >> > > etc.) during the VM install phase. This piece of data is important >> > > post-install though: if the user adds a new disk to the VM later, >> we want to >> > > be able to ask libosinfo about what devices the installed OS >> supports, so we >> > > can set optimal defaults, like enabling virtio. >> > > >> > > There isn't any standard libvirt XML field to track this kind of >> info >> > > though, so apps have to invent their own schema. nova and rhev do it >> > > indirectly AFAICT. gnome-boxes does it directly with XML like this: >> > > >> > >   <metadata> >> > >     <boxes:gnome-boxes >> xmlns:boxes="https://wiki.gnome.org/Apps/Boxes"> >> > >       <os-id>http://fedoraproject.org/fedora/28</os-id> >> > >       .... >> > >     </boxes:gnome-boxes> >> > >   </metadata> >> > > >> > > I want to add something similar to virt-manager but it seems a >> shame to >> > > invent our own private schema for something that most non-trivial >> virt apps >> > > will want to know about. I was thinking a schema we could >> document with >> > > libosinfo, something like >> > > >> > > <metadata> >> > >   <libosinfo >> > > xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0"... >> > >     <os-id>http://fedoraproject.org/fedora/28</os-id> >> > >   </libosinfo> >> > > </metadata> >> > >> > Yes, I would like to see this standardized under <matadata>. >> > >> >> Me too and what Cole suggested looks fine. > > It occurs to me that we actually need more than just the os-id value. > > When you query devices for a given OS, you'll often be told that multiple > devices are compatible, and the mgmt app can decide which of them to then > use. > > So if we want consistency when later hotplugging, we should make a record > of which devices we decided to use too, so if the mgmt app changes its > preference, we still know what we originally picked. > > eg to express that we use virtio-net and virtio-blk (even if virtio-scsi > was supported by the OS): > >   <metadata> >     <libosinfo > xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0"... >       <os id="http://fedoraproject.org/fedora/28"/> >       <device id="http://pcisig.com/pci/1af4/1000"/> >       <device id="http://pcisig.com/pci/1af4/1001"/> >     </libosinfo> >   </metadata> > > Note, I'm suggesting using an 'id' attribute, rather than naming the > element 'os-id', to be more closely aligned with osinfo schema. > I'm not against that <device id =''/> but it is going to take some effort to properly specify what is really meant by that.  The fact that some device model was chosen for a particular device does not necessarily mean that it is requested as the default.  It only means what is actually encoded in the XML already, that is a particular model for a particular device.