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

[Daniel P. Berrange]

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
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