Re: 2.6.28-rc1: NVRAM being corrupted on ppc64 preventing boot (bisected)

From: Mel Gorman
Date: Fri Oct 31 2008 - 14:37:17 EST


On Fri, Oct 31, 2008 at 10:10:55PM +1100, Paul Mackerras wrote:
> Mel Gorman writes:
>
> > Yaboot in my case and I've heard it affected a DVD installation. I don't
> > know for sure if it affects netboot but as I think it's something the
> > kernel is doing, it probably doesn't matter how it gets loaded?
>
> What changed in that commit was the contents of a couple of structures
> that the firmware looks at to see what the kernel wants from
> firmware. Specifically the change was to say that the kernel (or
> really the zImage wrapper) would like the firmware to be based at the
> 32MB point (which is what AIX uses) rather than 12MB (which was the
> default on older machines).
>
> So, as I understand it, it's not anything the kernel is actively
> doing, it's how the firmware is reacting to what the kernel says it
> wants. And since we are requesting the same value as AIX (as far as I
> know) I'm really surprised it caused problems.
>
> We can revert that commit, but I still need to solve the problem that
> the distros are facing, namely that their installer kernel + initramfs
> images are now bigger than 12MB and can't be loaded if the firmware is
> based at 12MB. That's why I really want to understand the problem in
> more detail.
>
> > It's been pointed out that it can be "fixed" by upgrading the firmware but
> > surely we can avoid breaking the machine in the first place?
>
> Have you upgraded the firmware on the machine you saw this problem on?
> If not, would you be willing to run some tests for me?
>

As per an off-line suggestion, I was able to get past the NVRAM problem
using the following patch. The machine still fails to fully boot but it's
due to some modules problem and unrelated to this issue.