Re: ABI coupling to hypervisors via CONFIG_PARAVIRT

[Ingo Molnar <mingo@elte.hu>]

* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> Now it may be that you've got a change that's absolutely great for 
> everyone, and the only blocker is that the FoobieVisor can't deal with 
> it.  OK, great, then you'd have a point.

yep. That's precisely my worry. And it doesnt have to be a 'great' thing 
- just any random small change in the kernel that makes sense: what is 
the likelyhood that it cannot be implemented, no matter what amount of 
insight, paravirt_ops + hyper-ABI emulation hackery, for FoobieVisor, 
because FoobieVisor messed up its ABI.

that likelyhood is a pure function of how FoobieVisor's hypercall ABI is 
shaped. Wow! So can you guess where my fixation about not having too 
many ABIs could possibly originate from? ;-)

Until today everyone on the hypervisor side of the argument pretended 
that paravirt_ops solves all problems and acted stupid when i said an 
ABI is an ABI is an ABI, and that "backwards compatibility" does have 
some technological consequences. _Now_ at least i've got this minimal 
admission that FoobieVisor _might_ break. Quite a breakthrough =B-)

	Ingo