Re: [Xen-devel] [libvirt] [PATCH] libxl: allow an <emulator> to be selected in the domain config XML

[Marek Marczykowski <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On 31.05.2013 10:25, Ian Campbell wrote:
> On Thu, 2013-05-30 at 11:53 -0600, Jim Fehlig wrote:
>> Marek Marczykowski wrote:
>>> On 01.05.2013 16:11, Daniel P. Berrange wrote:
>>>   
>>>> On Wed, May 01, 2013 at 02:44:11PM +0100, David Scott wrote:
>>>>     
>>>>> On 01/05/13 09:46, Ian Campbell wrote:
>>>>>       
>>>>>> I would suggest that libvirt+libxl expose the version as the "emulator"
>>>>>> option and not the path. Just leave the path as the default in the
>>>>>> normal case. You may also want to provide an extra
>>>>>> emulator-path-override tag/attribute/XML for advanced users, but that's
>>>>>> up to you.
>>>>>>
>>>>>> If you need to support upgrade from xend then you could perhaps treat
>>>>>> <emulator> values not in the set of valid LIBXL_DEVICE_MODEL_VERSION
>>>>>> string (currently "qemu-xen" and "qemu-xen-traditional") as a path to a
>>>>>> qemu-xen-traditional device model -- no xend user can possibly have been
>>>>>> using the new device model with xend. Or you could take the approach
>>>>>> that xl does and just warn.
>>>>>>         
>>>>> This would work for me: it doesn't seem too bad to consider
>>>>> "qemu-xen" and "qemu-xen-traditional" as special virtual paths. It's
>>>>> a useful observation that xend never supported the new device model.
>>>>> Jim: should I cook up patch v3? :-)
>>>>>       
>>>> No, that really doesn't fly. The <emlator> element must always point
>>>> to a qualfied binary path.
>>>>
>>>> IMHO, libvirt should just default to the new QEMU binary and if people
>>>> want to use the old one, they can configure the emulator path for it.
>>>>     
>>>
>>> What about stubdom? Any idea how to do it better than special paths? Even if
>>> given path will point to stubdom binary, I don't know how libvirt shoud
>>> distinguish it from standalone qemu and set b_info->device_model_stubdomain
>>> accordingly.
>>>   
>>
>> As mentioned in my reply to your stubdom patch, this should be handled
>> in libxl IMO.
> 
> The default is handled in libxl, so you don't need to do anything if you
> don't want to. It's up to you if you want to provide an override
> facility in libvirt. Personally I'd do it with a specific XML
> property/key/whatever rather than magic emulator paths...

Optional attribute for <emulator> tag? Maybe sth like:
<emulator type="stubdom">/usr/lib/xen/boot/ioemu-stubdom.gz</emulator>
?

-- 
Best Regards,
Marek Marczykowski
Invisible Things Lab

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