RE: [RFC] tmem ABI change... backwards compatibility unnecessary?

[Dan Magenheimer <dan.magenheimer@oracle.com>]

> > Thank goodness ABI versioning was built into tmem from
> > the beginning!
> 
> Hm, I'm not really a big fan of having a single "ABI version".  It
> always seems better to have individual calls which can be
> augmented/replaced by new calls, and/or have capability flags to extend
> the ABI.  Versions mean you end up being stuck doing updates in a very
> coarse-grained way, and the long-term support gets very onerous.
> (Microsoft ABIs are a good antipattern to avoid, especially DirectX.)

While I agree in general, and tmem can cleanly handle other forms
of minor updates as well, this ABI version change was very nice
for this case where the ops data structure (passed to the hypercall
in memory) changed in size, thus changing the interface for most of
the critical tmem operations.