2.6.28-rc1: NVRAM being corrupted on ppc64 preventing boot (bisected)
Mel Gorman
mel at csn.ul.ie
Fri Oct 31 22:31:16 EST 2008
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.
>
Same here, it sounds like an innocent change. While it is possible that AIX
could not work on this machine, it seems a bit unlikely.
> 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?
No. Luckily for us, it was scheduled to be upgraded but it got delayed
:). I've asked the guy to go somewhere else for a while so I should be able
to keep the machine in the state it's currently in.
> If not, would you be willing to run some tests for me?
>
Of course.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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