Re: [Qemu-devel] [PULL 25/26] block: Remove deprecated -drive option serial

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Jun 22, 2018 at 04:25:13PM +0200, Kevin Wolf wrote:
> Am 22.06.2018 um 15:36 hat Christian Borntraeger geschrieben:
> > 
> > 
> > On 06/22/2018 02:55 PM, Kevin Wolf wrote:
> > > Am 22.06.2018 um 13:38 hat Christian Borntraeger geschrieben:
> > >>
> > >> On 06/15/2018 04:21 PM, Kevin Wolf wrote:
> > >>> The -drive option serial was deprecated in QEMU 2.10. It's time to
> > >>> remove it.
> > >>>
> > >>> Tests need to be updated to set the serial number with -global instead
> > >>> of using the -drive option.
> > >>
> > >> libvirt 4.5 still creates those (at least on s390x)
> > >>
> > >>     <disk type='file' device='disk'>
> > >>       <driver name='qemu' type='qcow2' cache='none' io='native' iothread='1'/>
> > >>       <source file='/var/lib/libvirt/qemu/image.zhyp137'/>
> > >>       <target dev='hda' bus='virtio'/>
> > >>       <serial>skel</serial>
> > >>       <boot order='1'/>
> > >>       <address type='ccw' cssid='0xfe' ssid='0x0' devno='0x0000'/>
> > >>     </disk>
> > >>
> > >>
> > >> -> 
> > >> [...]
> > >> -drive file=/var/lib/libvirt/qemu/image.zhyp137,format=qcow2,if=none,id=drive-virtio-disk0,serial=skel,cache=none,aio=native -device virtio-blk-ccw,iothread=iothread1,scsi=off,devno=fe.0.0000,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,write-cache=on 
> > >> [...]
> > >>
> > >> 2018-06-22T11:25:20.946024Z qemu-system-s390x: -drive file=/var/lib/libvirt/qemu/image.zhyp137,format=qcow2,if=none,id=drive-virtio-disk0,serial=skel,cache=none,aio=native: Block format 'qcow2' does not support the option 'serial'
> > >> 2018-06-22 11:25:21.098+0000: shutting down, reason=failed
> > >>
> > >> So it seems that this breaks s390x.
> > 
> > To me it seems that this is also broken on x86.
> > > 
> > > Thanks for bringing this up. libvirt should fix this before QEMU 3.0 is
> > > released.
> > 
> > I think this is definitely too short notice. We should not break existing
> > setups just by insisting that users have to update libvirt when they update
> > QEMU. Yes, this might be our policy, but doing so "just because we can"
> > is certainly a very bad attitude. I see no fundamental technical reason why
> > we should not revert this change.
> 
> This was in fact one release longer than our deprecation policy says.
> Are we serious about the deprecation policy or aren't we?
> 
> I might consider reverting a change if it turned out that this requires
> some massive work in libvirt. But I think this one should be rather easy
> to fix in libvirt until 3.0 is released.

I've got a patch mostly ready that converts libvirt to setting these things
on the frontend device, however, I've got some queries...

 - usb-storage  - doesn't appear to support geometry or werror/rerror

   Will we loose functionality by stopping use of -drive for werror

   Loosing geometry feels relevant too, unless it was already ignored
   when set opf -drive ?

 - SD card - requires -drive with if=sd, no -device support AFAICT

   Will we loose functionality be stopping use of -drive for if=sd, or
   is this stuff ignored anyway ?

 - ide-cd/scsi-id - doesn't support geometry

   Presumably becuase its irrelevant for CDs


Regards,
Daniel
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