Re: [libvirt] domain XML for tracking libosinfo ID

On 09/06/2018 09:04 AM, Martin Kletzander wrote: > 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. > Yeah I'm a bit confused by this as well, it's not exactly clear to me how we would use or set XML like that for virt-manager, and how other apps would be expected to consume it. I'll start with the <os id=X/> bit and we can revisit the <device id=X/> later