newbus IO ordering semantics - moving forward

[John-Mark Gurney]

Adrian Chadd wrote this message on Fri, Oct 28, 2011 at 04:28 +0800:
> So what I'm proposing is:
> 
> * Make the bus default to use ordered semantics, much like what Linux
> does - ie, all IO read/writes (io or memory) are in-order and flushed
> with a barrier;
> * Add an option which allows the driver to request a region with
> loose-running/lazy semantics, what we're supposed to have now, and
> then leave barriers up to the driver;
> * Print out something nice and loud if a driver decides to use the
> lazy/loose semantics, which may result in unpredictable behaviour on
> non-{i386,amd64}.
> 
> I'd appreciate some feedback/comments before I go off and code all of this up.

I think we should complain about the drivers that are NOT using the
lazy/loose semantics as those are the drivers that are slower than
they should be, and/or not written properly.  Complaining about properly
written drivers that use the lazy/loose semantics when they get updated
to be correct is wrong...

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."