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From: Markus Armbruster <armbru@redhat.com>
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Date: Fri, 22 Jun 2018 16:19:29 +0200
In-Reply-To: <20180622125502.GF4366@localhost.localdomain> (Kevin Wolf's
	message of "Fri, 22 Jun 2018 14:55:02 +0200")
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Subject: Re: [Qemu-devel] [PULL 25/26] block: Remove deprecated -drive
 option serial
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To: Kevin Wolf <kwolf@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>, Boris Fiuczynski <fiuczy@linux.ibm.com>, qemu-block@nongnu.org, libvir-list@redhat.com, qemu-devel@nongnu.org, pkrempa@redhat.com

Kevin Wolf <kwolf@redhat.com> writes:

> 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.
>
> Thanks for bringing this up. libvirt should fix this before QEMU 3.0 is
> released.
>
> Sadly, it also shows that deprecation warnings in log files go
> unnoticed.

Nobody reads log files until things have gone belly up, and even then
unrelated log entries get ignored.

The way to get deprecation warnings noticed it to have the management
application fail its "make check".

Perhaps we could use a more structured notification, to make detecting
use of deprecated features programmatically trivial.  A QMP event might
do.