Re: [Xen-devel] [Hackathon] libvirt session notes

[George Dunlap <dunlapg@xxxxxxxxx>]

On Tue, Jun 3, 2014 at 11:41 AM, Fabio Fantoni <fabio.fantoni@xxxxxxx> wrote:
> Il 03/06/2014 11:41, Lars Kurth ha scritto:
>
>> Thank you to Anil for taking notes.
>> Lars
>>
>> == Attendees ==
>> daniel berrange (redhat)
>> george dunlap (citrix)
>> ian jackson (citrix)
>> dario (citrix)
>> dave scott (citrix)
>> olivier lambert (Vates)
>> julien fontanet  (Vates)
>> dan keningsberg (ovirt lead)
>> john garbutt (rackspace)
>> ?? (rackspace)
>>
>> == what is it overview? ==
>>
>> JonL describes the xapi project and how it fits together with the
>> toolstacks.  xend being deprecated for xen 4.5 (planned), and replaced by
>> libxl.  libxl is a C interface that's designed to be backwards compatible.
>> libxl in xen 4.4 has forward API compatibility, but not backwards (but this
>> is not as important).
>>
>> Some features such as cancellation are discussed.  libxl has no support
>> for task cancellation. Daniel says that libvirt has some support for job
>> cancellation, but not all operations (only the ones designated as
>> asynchronous ones).
>>
>> Live migration: multiple apis in libvirt for migration, none are supported
>> xl. Dario suggests that we'll have some migration soon in libxl.  libvirt
>> doesnt require that all hypervisor drivers support the same features, but
>> enumerates things like device models.
>>
>> GeorgeD points that out that implementation details from one hypervisor
>> can leak through (e.g. USB models).  DanielB notes that much of the Xen
>> basics are already in libvirt due to the xend support.
>>
>> libvirt's approach is to be quite explicit when talking to underlying
>> layers, to ensure that it doesn't depend on defaults change downstream in
>> the future.  Discussion of machine types in libvirt and how this interacts
>> with various drivers.   Some hypervisor-specific features like qemu monitor
>> support are put into a separate libvirt-qemu library, that can be deprecated
>> more easily than if they were integrated directly.
>>
>> How do these tools all interact if you use them at the same time? Overall,
>> libxl is stateless and so tries to deal with other things working on the
>> host.
>>
>> IanJ asks about consoles.  There's a notification mechanism in libvirt
>> that can be wired up for this, and libvirt has a more extensible design to
>> make it easier to hook this stuff in.
>>
>> Who is using libvirt?  There are now automated libvirt tests as part of
>> osstest (IanJ/GeorgeD/IanC).  So new versions of libvirt are tested to see
>> if they break Xen, and vice versa.  Does not include live migration yet.
>>
>> Is there a libxl to libvirt xml -- feed it an xm config file and some
>> fixing up.  Not fully ported to xl yet, but all agree this would be useful
>> to have on the wiki.  IanJ suggests it'll be useful to take the libxl config
>> parser and expose the struct directly.
>>
>> == What's not supported in libvirt?  ==
>>
>> Migration is known.  DaveS notes that networking also had problems since
>> default networking type isn't supported.  There's a list of APIs support and
>> which work under Xen. virt-manager is a good one to test, but it exposes too
>> many options (e.g. Spice on qemu) which wont work on Xen.
>
>
> I use spice on xen since the end of 2011.
> What is your problem with spice on xen exactly? Lack of domUs pv support? Is
> it some spice option supported in libvirt (with kvm) but not supported in
> libxl yet?

libxl supports spice, and the libvirt driver for KVM knows how to
enable spice, but I don't think the libvirt driver for libxl knows how
to enable it in libxl yet.

 -George

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