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

[Paul Mackerras]

Mel Gorman writes:

> On some ppc64 machines, NVRAM is being corrupted very early in boot (before
> console is initialised). The machine reboots and then fails to find yaboot
> printing the error "PReP-BOOT: Unable to load PRep image".  It's nowhere near
> as serious as the ftrace+e1000 problem as the machine is not bricked but it's
> fairly scary looking, the machine cannot boot and the fix is non-obvious. To
> "fix" the machine;
> 
> 1. Go to OpenFirmware prompt
> 2. type dev nvram
> 3. type wipe-nvram
> 
> The machine will reboot, reconstruct the NVRAM using some magic and yaboot
> work again allowing an older kernel to be used. I bisected the problem down
> to this commit.

Eek!

Which ppc64 machines has this been seen on, and how were they being
booted (netboot, yaboot, etc.)?

Is it just the Powerstations with their SLOF-based firmware, or is it
IBM pSeries machines as well?

Paul.