On Tue, Jan 22, 2008 at 09:36:27PM +0100, Pavel Cahyna wrote:
> On Tue, Jan 22, 2008 at 02:29:12PM +0100, Joerg Sonnenberger wrote:
> > On Mon, Jan 21, 2008 at 10:12:38PM +0100, Manuel Bouyer wrote:
> > > I think setting it to a smaller value should work. Setting it to something
> > > larger than 0xc0000000 will be a real pain to support for PAE.
> > > Linux also has the kernel loaded at 0xc0000000, and the PAE support in
> > > Xen was really designed for this case.
> > 
> > Not changing it makes it also a lot easier to enable PAE by default.
> > That's desirable to be able to use syscall for example.
> 
> Changing KERNBASE (downwards) is the official workaround for buffer cache
> issues on machines with large RAM (that is machines which could benefit
> from PAE).

in the Xen case, you've got another workaround: decrease the size of
your ram size in the domain (and so you can get more domains :) 
Note that changing KERNBASE in a native PAE kernel that would use this pmap
wouldn't be an issue.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--