[PATCH v2] powerpc/64s: introduce CONFIG_MAXSMP to test very large SMP

[Nicholas Piggin]

Excerpts from Nicholas Piggin's message of November 23, 2021 3:14 pm:
> Excerpts from Michael Ellerman's message of November 23, 2021 11:01 am:
>> Michael Ellerman <mpe at ellerman.id.au> writes:
>>> Christophe Leroy <christophe.leroy at csgroup.eu> writes:
>>>> Le 09/11/2021 à 07:51, Nicholas Piggin a écrit :
>>> ...
>>>>> diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
>>>>> index a208997ade88..14c275e0ff93 100644
>>>>> --- a/arch/powerpc/platforms/Kconfig.cputype
>>>>> +++ b/arch/powerpc/platforms/Kconfig.cputype
>>>>> @@ -475,9 +475,14 @@ config SMP
>>>>>   
>>>>>   	  If you don't know what to do here, say N.
>>>>>   
>>>>> +# MAXSMP sets 8192 if COMPILE_TEST because that's what x86 has flushed out.
>>>>> +# Exceeding that will cause a lot of compile errors. Have to deal with those
>>>>> +# first.
>>>>>   config NR_CPUS
>>>>> -	int "Maximum number of CPUs (2-8192)" if SMP
>>>>> -	range 2 8192 if SMP
>>>>> +	int "Maximum number of CPUs (2-8192)" if SMP && !MAXSMP
>>>>> +	range 2 16384 if SMP
>>>>> +	default 16384 if MAXSMP && !COMPILE_TEST
>>>>> +	default 8192 if MAXSMP && COMPILE_TEST
>>>>
>>>> You can do less complex. First hit becomes the default, so you can do:
>>>>
>>>> 	default 8192 if MAXSMP && COMPILE_TEST
>>>> 	default 16384 if MAXSMP
>>>
>>> I did that when applying.
>> 
>> But I'll have to drop it, it breaks the allyesconfig build:
> 
> Ah, you still need patch 1/2 sorry I confused things by only re-sending 
> this one.
> 
> https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20211105035042.1398309-1-npiggin@gmail.com/

Actually KVM will also be broken, I sent a patch for it but there is 
some discussion of fixing it a different way. So maybe leave out the
maxsmp patch for now (or make it depend on BROKEN?). I can re-send
maybe next merge window if the other pieces are in place.

If you could still take that ^^ patch for now would be good though.

Thanks,
Nick