[libvirt] attach-device error: XML error: unknown device type

[Michal Privoznik]

On 03.07.2013 20:34, Chris Evich wrote:
> On 07/03/2013 09:46 AM, Daniel P. Berrange wrote:
>> On Wed, Jul 03, 2013 at 09:44:46AM -0400, Chris Evich wrote:
>>> Hi,
>>>
>>> On Fedora 18 (libvirt 0.10.2.6-1) I'm trying to add a new serial device
>>> to a KVM VM with:
>>>
>>> virsh attach-device foobar /tmp/serial.xml
>>>
>>> and I keep getting:
>>>
>>> error: Failed to attach device from /tmp/serial.xml
>>> error: XML error: unknown device type
>>>
>>> with serial.xml:
>>>
>>> <serial type='file'>
>>>   <source path='/tmp/serialfile'/>
>>>   <target port='1'/>
>>> </serial>
>>>
>>> Though I tried it w/o the <target> tag, with and without the --config
>>> flag, and with and without the guest running.  Assuming it's similar, I
>>> tried and was successful in adding this device via virt-manager, though
>>> it complains if the VM is running (which is fine).
>>>
>>> What am I doing wrong with the virsh attach-device command or XML?
>>
>> There is no support for hotplug of any character device (that
>> covers serial, parallel, console, channnel elements in the XML)
>>
>>
>> Daniel
>>
> 
> Oops, sorry, should have been more clear than "and with and without the
> guest running".
> 
> * I see the 'unknown device type' error when guest is running and I run
>   "virsh attach-device foobar /tmp/serial.xml --config".
> 
> * I also get 'unknown device type' error when guest is NOT running, and
>   I run "virsh attach...." both with or without '--config' flag.
> 
> * I see the 'unknown device type' error inside the "details" window
>   when the guest is running and I use virt-manager.
> 
> * I do NOT get any error, and the device is attached, when I use
>   virt-manager, and the guest is NOT running (or by clicking yes
>   after getting error in above bullet).
> 
> The main difference in using virt-manager, is that I'm selecting the
> file type and entering in the values manually instead of in an XML file.

This works as expected. Device attach implementation currently doesn't
know how to handle <serial/> or any other character device. It doesn't
matter if you're doing --live or --config hotplug. However, if you are
trying virt-manager on a not running guest, then I guess virt-manager is
just clever enough to redefine the domain and not call any hotplug API.
This is equivalent to:

# virsh destroy $guest
# virsh edit $guest (insert desired chardev XML snippet)
# virsh start $guest


Michal
> 
> A loosely-related problem is with serial-hot plug (which is expected to
> not work).  The error message reported under details is the same/similar
> 'device type error'.  Whereas I was expecting something more specific
> like a "Can't hotplug this" error (see screenshot).

Yes, the error message can be misleading.

Michal