[libvirt] New libvirt-tck failure with libvirt 5.2.0

[Daniel Henrique Barboza]

On 4/10/19 3:33 PM, Jim Fehlig wrote:
> On 4/10/19 12:25 PM, Daniel Henrique Barboza wrote:
>>
>>
>> On 4/10/19 3:08 PM, Jim Fehlig wrote:
>>> I noticed libvirt-tck test domain/207-disk-media-change.t started 
>>> failing after updating to libvirt 5.2.0. A bisection fingered commit 
>>> f1d65853
>>>
>>> commit f1d6585300001c7b23b8796a0faa4411c3531996
>>> Author: Daniel Henrique Barboza <danielhb413 at gmail.com>
>>> Date:   Fri Mar 15 18:06:45 2019 -0300
>>>
>>>     domain_conf: check device address before attach
>>>
>>> This commit prevents a media change on CDROM devices.
>>
>> Thanks for letting us know. I'll run libvirt-tck (any pointers are 
>> appreciated -
>> first time I've heard about this test suite) and see if I can get a 
>> fix going.
>
> It's easy to reproduce outside of libvirt-tck. Simply start a VM with 
> a cdrom device and then try to update the <source> element with 'virsh 
> attach-device ...'. E.g. with the VM running try to "eject" the cdrom
>
> # cat update-empty-cdrom.xml
> <disk type='file' device='cdrom'>
>   <target dev='hdc'/>
> </disk>
>
> # virsh attach-device test update-empty-cdrom.xml
> error: Failed to attach device from update-empty-cdrom.xml
> error: Requested operation is not valid: Domain already contains a 
> device with the same address


To give a background on this patch, this was intended to avoid a situation
where a hotplug of a device with the same ID would fall back to a cleanup
code that ended up unplugging the previous existing device in the guest.
This was happening when using the QEMU driver.

What I didn't expect is for a CD-ROM media to be changed using a
attach-device command. I think that the CD-ROM type has specific rules 
of not
hot-unplugging itself (i.e. the driver) in the situation I described 
above. What
I was expecting for CDROM change media was a VIR_DOMAIN_DEVICE_ACTION_UPDATE
action instead, so this usage completely went under the radar for that
patch.

In fact, there are "update-device" and "change-media" commands that,
according to the man page, are meant for the purpose of media change.
However, the same man page doesn't prohibit the use of attach-device
for media change either. I am not sure why have a change-media command
if attach-device is supposed to handle media change as well, but for
now let's fix the usage of attach-device with CDROM.


Thanks,


DHB



>
> Regards,
> Jim