[libvirt] [RFC] libxenlight driver

[Jim Fehlig]

I'm looking into creating a driver for the new Xen xl/libxl toolstack
(aka libxenlight [1]), set to become the default in upcoming Xen 4.1.0
release.

My first hurdle is deciding whether this should be a new driver or
integrated with existing xen-unified driver.  Initially I thought a new
driver would be a better approach - a clean break from the old code,
similar to the xenapi driver.  libxenlight is also stateless (no managed
domains), which seems like another good argument for a new driver.  But
libxenlight is really just another interface into the same hypervisor,
so in that regard it should be a xen-unified subdriver.

There are certainly benefits to the xen-unified subdriver approach, e.g.
the existing hypervisor and xenstore subdrivers can be leveraged, the
former providing all the capabilities code.  But AFAIK, libxenlight and
xend should not be used together, so I don't think we would want the
xend subdriver activated if libxenlight is detected.  Supposedly xl can
be used as a direct replacement for xm, allowing unconditional use of
that subdriver.

BTW, Ian Jackson responded [2] to some of my questions regarding
compatibility between old and new toolstack if you are interested.

I'd like to hear other's opinions on a new driver vs. a xen-unified
subdriver.

Regards,
Jim

[1] http://lists.xensource.com/archives/html/xen-devel/2009-11/msg00436.html
[2]
http://lists.xensource.com/archives/html/xen-devel/2010-11/msg00344.html