On Thu, Nov 29, 2007 at 01:48:56PM +0100, Christoph Egger wrote:
> On Wednesday 28 November 2007 15:58:10 Manuel Bouyer wrote:
> > Hi,
> >
> > On Wed, Nov 28, 2007 at 02:49:17PM +0100, Christoph Egger wrote:
> > > Hi Manuel!
> > >
> > > I just noticed your xenkernel3 package update:
> > >
> > > RCS file: /cvsroot/pkgsrc/sysutils/xenkernel3/patches/patch-ba,v
> > > Working file: patch-ba
> > > head: 1.2
> > > branch:
> > > locks: strict
> > > access list:
> > > symbolic names:
> > >         pkgsrc-2007Q3: 1.1.0.2
> > >         pkgsrc-2007Q3-base: 1.1
> > > keyword substitution: kv
> > > total revisions: 2;     selected revisions: 2
> > > description:
> > > ----------------------------
> > > revision 1.2
> > > date: 2007/11/26 19:35:25;  author: bouyer;  state: Exp;  lines: +12 -3
> > > Properly initialize physaddr_bitsize for native 64bit dom0. Makes
> > > NetBSD/xenamd64 boot on systems with more than 4Gb RAM.
> > > Bump pkgrevision.
> > >
> > >
> > > Looking at the diff, you unconditionally initialize
> > > d->arch.physaddr_bitsize. Are you sure this is correct for 32bit / 32bit
> > > pae Dom0 ?
> > >
> > > Further, for 64bit xen-kernels this is already initialized some lines
> > > further below and overrides your hardcoded value. So I don't understand
> > > in which way your patch fixes the boot problem with more than 4GB RAM.
> > >
> > > Can you explain this, please?
> 
> Thank you for the explanation.
> 
> > I tracked down my problem with more than 4GB RAM to
> > d->arch.physaddr_bitsize being 0 in domain_clamp_alloc_bitsize(). This
> > cause all attemps to XENMEM_increase_reservation with bits > 0 to fail
> 
> More precisely, __alloc_domheap_pages() returns NULL. This impacts
> Xen heap allocation in general and on featurewise this impacts ballooning and 
> NUMA support in Xen.
> 
> It makes no difference if the Linux Dom0 has 1GB or 7GB.
> I don't understand how this can show no effect on Linux Dom0.

I don't know how linux deals with devices that can't acces memory above
4GB. This is where NetBSD failed, when allocating DMA-safe memory.

> > So, if I got it right, my patch should cause physaddr_bitsize to be 64 by
> > default, and set to some other value later if needed; and if "not needed"
> > 64 is the right value. If the hypervisor is not 64bits, physaddr_bitsize
> > isn't used at all anyway.
> 
> That's right.
> I submitted the patch.
> 

Thanks !

-- 
Manuel Bouyer, LIP6, Universite Paris VI.           Manuel.Bouyer@lip6.fr
     NetBSD: 26 ans d'experience feront toujours la difference
--