Re: [libvirt] [PATCH] qemu: match controller index for LIVE+CONFIG when doing hotplug
On Sat, Jun 25, 2016 at 03:42:38PM +0200, Tomasz Flendrich wrote:
> On 24 Jun 2016, at 13:25, Martin Kletzander <mkletzan(a)redhat.com> wrote:
>> And what about the current bad behavior when you do this?
>>
>> virsh attach interface f24 --type network --source default --live
>> virsh attach interface f24 --type network --source default --live
>> --config
>>
>
> This can be separated into two different issues. If you do
> attach-interface, we generate an XML without address, so you should be
> able to do the above and have 2 more interfaces live, the second one
> would be identical to the only one added to config.
What if we guaranteed that adding a device with both “—live —config” options
at once would always generate the same address? It could even leave some
holes (unassigned addresses) in one of {config, live}, but it doesn’t bother us,
does it? It would make the ABI stable.
If finding such address would be impossible, the user would be informed that
he/she can try adding the device separately using two calls without ABI stability.
This solution means that there are less surprises for the user.
Is there any reason it can’t be done, apart from complicating the code?
That's what we were talking about and that's what we need to do =)
There is no reason it can't be done.
Besides, how often do people run —live without —config? Perhaps we
should
figure out what the most common use case is, make it work flawlessly
and have some undesired behavior in other cases as a compromise.
It's hard to guess. However when concentrating on the guarantee of ABI
stability, it's pretty clear how it should behave from the user's POV.
- when both live and config are used, the devices plugged there must be
identical, i.e. anything generated must be the same, all addresses, etc.
- when you can't plug identical devices to both config and live
definitions, just error out. Of course the more descriptive error
message there is, the better.
Have a nice day,
U2
Tomasz
Martin
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