Re: [Qemu-devel] [PATCH v6 2/7] hw/misc: add vmcoreinfo device

[Michael S. Tsirkin]

On Mon, Oct 09, 2017 at 02:02:18PM +0100, Daniel P. Berrange wrote:
> On Mon, Oct 09, 2017 at 02:43:44PM +0200, Igor Mammedov wrote:
> > On Mon, 9 Oct 2017 12:03:36 +0100
> > "Daniel P. Berrange" <address@hidden> wrote:
> > 
> > > On Mon, Sep 11, 2017 at 06:59:24PM +0200, Marc-André Lureau wrote:
> > > > See docs/specs/vmcoreinfo.txt for details.
> > > > 
> > > > "etc/vmcoreinfo" fw_cfg entry is added when using "-device vmcoreinfo". 
> > > >  
> > > 
> > > I'm wondering if you considered just adding the entry to fw_cfg by
> > > default, without requiring any -device arg ? Unless I'm misunderstanding,
> > > this doesn't feel like a device to me - its just a well known bucket
> > > in fw_cfg IIUC ?  Obviously its existance would need to be tied to
> > > the latest machine type for ABI reasons though. The benefit of this
> > > is that it would "just work" without us having to plumb it through to
> > > all the downstream applications that use QEMU for mgmt guest (OpenStack,
> > > oVirt, GNOME Boxes, virt-manager, and countless other mgmt apps).
> > it follows model set by pvpanic device, it's easier to manage from migration
> > POV, one could use it even for old machine types with new qemu (just by 
> > adding
> > device, it makes instance not backwards migratable to old qemu but should 
> > work
> > for forward migration) and if user doesn't need it, device could be just 
> > omitted
> > from CLI.
> 
> Sure but it means that in effect no one will have this functionality enabled
> for several years. pvpanic has been around a long time and I rarely see it
> present in configured guests :-(
> 
> 
> Regards,
> Daniel

libvirt runs with -nodefaults, right? I'd argue pretty strongly -nodefaults
shouldn't add optional devices anyway.

So it's up to you guys, you can add it to VMs by default if you want to.


> -- 
> |: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
> |: https://libvirt.org         -o-            https://fstop138.berrange.com :|
> |: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|