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SubjectRe: Regression in 5.1.0-rc2: PowerBook G4 Aluminum fails to boot - bisected to commit 0df977eafc792
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Le 25/03/2019 à 01:49, Larry Finger a écrit :
> A build of kernel 5.1.0-rc2 resulted in a failure to boot on my
> PowerBook G4 Aluminum. The bootstrap loads the initial kernel and issues
> the appropriate start, but the machine hangs at that point.
>
> The problem does not depend on the choice of PPC32 processor type. This
> machine has a 7447A according to /proc/cpuinfo.
>
> The problem was bisected to the following:
>
> commit 0df977eafc792a5365a7f81d8d5920132e03afad
> Author: Christophe Leroy <christophe.leroy@c-s.fr>
> Date:   Thu Feb 21 10:37:54 2019 +0000
>
>     powerpc/6xx: Don't use SPRN_SPRG2 for storing stack pointer while
> in RTAS
>
>     When calling RTAS, the stack pointer is stored in SPRN_SPRG2
>     in order to be able to restore it in case of machine check in RTAS.
>
>     As machine check is not a perfomance critical path, this patch
>     frees SPRN_SPRG2 by using a field in thread struct instead.
>
>     Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
>
> I reverted this patch and found that the system began execution, and
> then failed, likely due to the reassignment of SPRN_SPRG2.
>
> I had found this problem with 5.1.0-rc1, but -rc2 was out by the time I
> finished the bisection. Unfortunately, none of the changes in -rc2 fixed
> the problem.

I think I identified the issue, see
https://patchwork.ozlabs.org/patch/1063962/

It is now booting properly under QEMU with your .config

Could you please test it on your target ?

Thanks
Christophe

>
> Attached is the .config that I used.
>
> Thanks,
>
> Larry

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