Re: [PATCH 3/3] m68k: allow kexec on all MMU enabled CPUs

[Greg Ungerer <gerg@linux-m68k.org>]

Hi Geert,

On 26/8/22 17:44, Geert Uytterhoeven wrote:
> On Fri, Aug 26, 2022 at 6:08 AM Greg Ungerer <gerg@linux-m68k.org> wrote:
>> The configuration setting for 68k kexec support limits it to only
>> the classic 68k CPU types (so no ColdFire). However the underlying
>> support can handle any 68k CPU that is MMU enabled - and that includes
>> ColdFire. (Of course that support is only as good as mentioned in
>> the current configuration help).
>>
>> None of the no-MMU CPU types (classic or ColdFire) have support for
>> kexec yet, so the configuration as it stands is not quite right, and
>> it will fail to compile on them.
>>
>> Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
> 
> Thanks for your patch!
> 
>> --- a/arch/m68k/Kconfig
>> +++ b/arch/m68k/Kconfig
>> @@ -87,7 +87,7 @@ config MMU_SUN3
>>
>>   config KEXEC
>>          bool "kexec system call"
>> -       depends on M68KCLASSIC
>> +       depends on MMU
>>          select KEXEC_CORE
>>          help
>>            kexec is a system call that implements the ability to shutdown your
> 
> Don't you need changes to arch/m68k/kernel/relocate_kernel.S,
> which supports 68020+ only?

I suspect so looking at that now. It compiles ok, but without a
check for MMU type specific to ColdFire it will likely fail.
I didn't dig into it too deeply, my primary goal with to fix compilation
for the non-MMU targets.

I started out testing it with this:

     depends on M68KCLASSIC && MMU

And that works and fixes the problem I was most interested in.
But then I figured that perhaps it is better to allow if for ColdFire with MMU enabled.

I didn't want to go down the rabbit hole of trying to get it working
on non-MMU platforms (and ColdFire with MMU enabled either really).

So I would be just as happy to limit it to M68KCLASSIC and MMU for now?

Regards
Greg



> Gr{oetje,eeting}s,
> 
>                          Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                  -- Linus Torvalds