Re: Regression in 5.1.0-rc2: PowerBook G4 Aluminum fails to boot - bisected to commit 0df977eafc792

[Larry Finger]

On 3/25/19 3:46 AM, Christophe Leroy wrote:
> Le 25/03/2019 Ã 01:49, Larry Finger a ÃcritÂ:
> > 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@xxxxxx>
> > Date:ÂÂ Thu Feb 21 10:37:54 2019 +0000
> >
> > ÂÂÂÂ powerpc/6xx: Don't use SPRN_SPRG2 for storing stack pointer while in RTAS
> >
> > ÂÂÂÂ When calling RTAS, the stack pointer is stored in SPRN_SPRG2
> > ÂÂÂÂ in order to be able to restore it in case of machine check in RTAS.
> >
> > ÂÂÂÂ As machine check is not a perfomance critical path, this patch
> > ÂÂÂÂ frees SPRN_SPRG2 by using a field in thread struct instead.
> >
> > ÂÂÂÂ Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> > ÂÂÂÂ Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> >
> > 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. That patch fixes the issue.

Larry