Re: [Xen-devel] [RFC] Enabling live-migrate on HVM on qemu-xen device model

[Alex Bligh <alex@xxxxxxxxxxx>]

Ian,

--On 17 December 2012 12:01:52 +0000 Ian Campbell <Ian.Campbell@xxxxxxxxxx> 
wrote:

> It's definitely at least a bug in the documentation -- this isn't a
> feature which was forgotten about, it was explicitly decided hadn't met
> the 4.2 deadline and wasn't going to be ready in time to wait for. This
> should have been documented and in the release notes etc, sorry.
>
> We did at least manage to tag it tech preview in
> http://wiki.xen.org/wiki/Xen_Release_Features which implies that it is
> not yet fully formed.
It is indeed tagged as 'tech preview'.

But given that:
a) HVM is hardly uncommon
b) live-migrate is pretty essential
c) qemu-xen device model is the default next time around and the /only/
  way you can achieve certain things (e.g. rebaseable snapshots)
d) the code is already written (at least for -unstable) and the patch is
  smallish (particularly if the JSON stuff is ignored)

... I'd suggest a backport to 4.2.x is a reasonable request. I've had a
first go at the libxl part and Stefano got their first and volunteered
to do the qemu bit (if he doesn't have time I can have a go at that too).

If necessary we can guard the code either with a compile time switch or
(as the wiki page suggested to me) a hypervisor command line switch like
TMEM and AVX, which if it's not enabled would just error the call in the
same way libxl does at the moment.

--
Alex Bligh

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