Re: The virtuailization patches break Voyager.

[Andi Kleen <ak@suse.de>]

On Saturday 28 April 2007 09:52:30 Jeremy Fitzhardinge wrote:
> Eric W. Biederman wrote:
> > Next time I'm in a really tormenting mood I will fire up my 
> > my ibm ps2 with it's 16Mhz 386 and 6MB and verify that all is working
> > well there.
> >   
> 
> Well, that would be interesting. From a subarch perspective, it would
> just be the normal default, and in theory it should work fine. But I
> suspect the fpu emulator is probably broken, and non-WP is likely to
> have rotted, 

AFAIK it's been tested occasionally on some embedded 386 systems
(e.g. by Thomas Gleixner). Probably not with the recent changes though. 

> and lots of other things. Is that an MCA machine? 

Yes should be.
 
> > I really don't think it is ok to be cavalier about anything
> > that we actually support.  Usually if we can handle the general
> > case it makes for better more maintainable code.
> >
> > So far the paravirt class of machines seems every bit as much a subarch
> > as voyager and every bit as interesting.
> >   
> Well, not really. The problem with the subarch mechanism is that it
> promotes a lot of copied code with small modifications, and so making
> changes is the inherently non-general activity of trying to find all the
> various copies, work out what subtle differences they have, and try to
> make the appropriate changes in each case. This was one of the major
> objections to the original Xen-as-subarch patches, and it is the problem
> with Voyager. The mass of preprocessor tricks doesn't help either.

Yes I agree. Current i386 subarch is a mess and I hope to slowly phase
it out. mach-{es7000,summit} should just be folded into mach-generic
always (like x86-64) and I'm somewhat hoping that mach-voyager and 
perhaps mach-visws too will just go away at some point.

The future direction are focussed pluggable interfaces like genapic, smp_ops etc.

-Andi