Re: [Qemu-devel] [RFC PATCH 0/4] per-object libraries

[Stefan Hajnoczi <stefanha@gmail.com>]

On Sun, Jun 30, 2013 at 08:49:28PM +0400, Michael Tokarev wrote:
> 30.06.2013 19:51, Peter Maydell wrote:
> > On 30 June 2013 16:36, Michael Tokarev <mjt@tls.msk.ru> wrote:
> >> I don't understand.  I for one like to see a plugins system used in qemu,
> >> and except of the build system everything else is easy (and even nice,
> >> there's even no need to load all plugins at startup as was initially
> >> suggested).  But for this to work, we really need to separate libs
> >> used only by plugins from the main lot, -- or else there's just no
> >> reason to build plugins in the first place.
> > 
> > So, why do we want to build things as plugins? Neither of the
> > cover letters to your two patch series nor Anthony's wiki page
> > on modules actually give the rationale.
> 
> I just updated the wiki page a bit (which is at
> http://wiki.qemu.org/Features/Modules btw).
> 
> The main rationale so far is to allow separate packaging of separate
> features for downstreams, to reduce the need to install all dependent
> libraries/packages.

This is more than just a small packaging clean-up.  It makes the
difference between shipping and not shipping niche features.

For features like Ceph, Sheepdog, etc the majority of downstream users
may be against the dependency.  So the QEMU package gets built without
these features!

Modules allow downstreams to cleanly package QEMU features and users can
decide which features/dependencies they wish to bring in.

For anyone jumping into the thread here: modules are not a stable ABI
and out-of-tree modules will not be supported in any way.

Stefan