Re: 2.6.23 boot failures on x86-64.

[Andi Kleen <ak@suse.de>]

On Monday 29 October 2007 19:47:47 Dave Jones wrote:
> On Mon, Oct 29, 2007 at 07:18:43PM +0100, Andi Kleen wrote:
>  > On Monday 29 October 2007 18:50:14 Dave Jones wrote:
>  > > We've had a number of people reporting that their x86-64s stopped booting
>  > > when they moved to 2.6.23.  It rebooted just after discovering the AGP bridge
>  > > as a result of the IOMMU init.
>  > 
>  > It's probably the usual "nobody tests sparsemem at all" issue.
> 
> We've been using SPARSEMEM in Fedora for a *long* time.
> So long in fact, I forget why we moved away from DISCONTIGMEM, so there's
> a significant number of users using that configuration for some time.

Supposedly you wanted a slower kernel that needs more memory? 

Ok I wasn't aware of that. I tended to get sparsemem reports usually
at least 1-2 releases after the fact, so it looked like it was undertested.

> 
>  > But if allocating bootmem >4G doesn't work on these systems
>  > most likely they have more problems anyways. It might be better
>  > to find out what goes wrong exactly.
> 
> Any ideas on what to instrument ?

See what address the bootmem_alloc_high returns; check if it overlaps
with something etc.

Fill the memory on the system and see if it can access all of its memory.

-Andi