Re: [Qemu-devel] TCG plugins and the GPL (was: [PATCH v4 00/54] plugins for TCG)

[Peter Maydell <peter.maydell@linaro.org>]

On Thu, 12 Sep 2019 at 11:07, Alex Bennée <alex.bennee@linaro.org> wrote:
> Peter Maydell <peter.maydell@linaro.org> writes:
> > Wait, what? From my perspective the whole point of the plugin
> > interface is that it should be stable, in that at least there's
> > a good chance that a plugin you built will work against multiple
> > versions of QEMU, and if it doesn't then it should fail with
> > a reasonable error message telling you to update. I'm not
> > sure we should be landing the plugins infrastructure if we
> > don't have that much stability.
>
> There is a big fat blurry line between "set in stone" and "not requiring
> you to re-engineer the plugin every QEMU release". I'm saying we should
> reserve the right to extend and change the plugin API as required but
> the expectation would be the plugins will continue to work the same way
> but maybe with tweaks to the API hooks to support additional features.
>
> It's also a pretty young interface so I would expect some evolution once
> it is released into the field.

Sure. But I think we should document that we at least intend to
have some approximation to a compatability/deprecation policy
here, and some mechanisms for versioning so you get a helpful
error rather than weird misbehaviour if your plugin is too old.

> One problem with the anti-license circumvention measures being suggested
> is it will mean having to recompile plugins for any given release.

Why should we do this? I think this is making life hard for our
users for no good reason. We *do* have this check for modules,
because a module is just a random .so that can do anything in
QEMU. I thought we had the TCG-plugin interface much more locked
down than that?

thanks
-- PMM