powerpc/rtas: fix early boot failure.

[Michael Ellerman]

On Mon, 2019-03-25 at 08:43:33 UTC, Christophe Leroy wrote:
> Commit 0df977eafc79 ("powerpc/6xx: Don't use SPRN_SPRG2 for storing
> stack pointer while in RTAS") changes the code to use a field in
> thread struct to store the stack pointer while in RTAS instead of
> using SPRN_SPRG2. It therefore converts all places which were
> manipulating SPRN_SPRG2 to use that field. During early startup,
> the zeroing of SPRN_SPRG2 has been replaced by a zeroing of that
> field in thread struct. But at least in start_here, that's done
> wrongly because it used the physical address of the fields while
> MMU is on at that time.
> 
> So the virtual address of the field should be used instead, but in
> the meantime, thread struct has already been zeroised and initialised
> so we can just drop this initialisation.
> 
> Reported-by: Larry Finger <Larry.Finger at lwfinger.net>
> Fixes: 0df977eafc79 ("powerpc/6xx: Don't use SPRN_SPRG2 for storing stack pointer while in RTAS")
> Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>
> Tested-by: Larry Finger <Larry.Finger at lwfinger.net>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/fd427103e8dfcb4b438269afd710b63e

cheers