[libvirt] [PATCH 3/3] scsi-disk: Deprecate device_id fallback to BlockBackend name

[Daniel P. Berrangé]

On Mon, Feb 04, 2019 at 10:56:28AM +0100, Kevin Wolf wrote:
> Am 29.01.2019 um 16:58 hat Daniel P. Berrangé geschrieben:
> > On Fri, Jan 25, 2019 at 06:46:53PM +0100, Kevin Wolf wrote:
> > > We should never have exposed BlockBackend names to the guest, it's a
> > > host detail. Deprecate this behaviour. Users who need to maintain the
> > > guest ABI can explicitly set the value with the device_id property.
> > 
> > I don't think we've deprecated things in the past which would cause
> > a guest ABI change when finally deleted.
> > 
> > Shouldn't we be instead setting using machine type versioning here,
> > so that existing machine types keep using the blk_name() fallback
> > forever, while QEMU 4.0+ machine types avoid blk_name() fallback
> > immediately.
> 
> I was going to implement this, but then I wondered if that's actually
> worthwhile. With -blockdev, you don't get the bad behaviour anyway, and
> tools that would select new machine types will hopefully also use new
> backend options.
> 
> So if we need to keep the bad behaviour around anyway instead of
> completely removing it as I intended originally, maybe -drive vs.
> -blockdev is enough to make the difference and we shouldn't change
> anything at the device model level at all.

Yeah, that rationale sounds ok to me.

Regards,
Daniel
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