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

[Michael Ellerman]

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:

  In file included from /home/michael/linux/arch/powerpc/include/asm/paravirt.h:15,
                   from /home/michael/linux/arch/powerpc/include/asm/qspinlock.h:6,
                   from /home/michael/linux/arch/powerpc/include/asm/spinlock.h:7,
                   from /home/michael/linux/include/linux/spinlock.h:93,
                   from /home/michael/linux/include/linux/mmzone.h:8,
                   from /home/michael/linux/include/linux/gfp.h:6,
                   from /home/michael/linux/include/linux/mm.h:10,
                   from /home/michael/linux/arch/powerpc/platforms/powernv/idle.c:9:
  /home/michael/linux/arch/powerpc/include/asm/cputhreads.h: In function ‘cpu_thread_mask_to_cores.constprop’:
  /home/michael/linux/arch/powerpc/include/asm/cputhreads.h:61:1: error: the frame size of 2064 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]
     61 | }
        | ^
  /home/michael/linux/arch/powerpc/platforms/powernv/idle.c: In function ‘store_fastsleep_workaround_applyonce’:
  /home/michael/linux/arch/powerpc/platforms/powernv/idle.c:220:1: error: the frame size of 2080 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]
    220 | }
        | ^
  cc1: all warnings being treated as errors
  make[4]: *** [/home/michael/linux/scripts/Makefile.build:287: arch/powerpc/platforms/powernv/idle.o] Error 1
  make[4]: *** Waiting for unfinished jobs....
  make[3]: *** [/home/michael/linux/scripts/Makefile.build:549: arch/powerpc/platforms/powernv] Error 2
  make[3]: *** Waiting for unfinished jobs....
  /home/michael/linux/arch/powerpc/kvm/book3s_hv_interrupts.S: Assembler messages:
  /home/michael/linux/arch/powerpc/kvm/book3s_hv_interrupts.S:66: Error: operand out of range (0x0000000000010440 is not between 0xffffffffffff8000 and 0x0000000000007ffc)
  make[3]: *** [/home/michael/linux/scripts/Makefile.build:388: arch/powerpc/kvm/book3s_hv_interrupts.o] Error 1
  make[3]: *** Waiting for unfinished jobs....
  make[2]: *** [/home/michael/linux/scripts/Makefile.build:549: arch/powerpc/platforms] Error 2
  make[2]: *** Waiting for unfinished jobs....
  make[2]: *** [/home/michael/linux/scripts/Makefile.build:549: arch/powerpc/kvm] Error 2
  make[1]: *** [/home/michael/linux/Makefile:1846: arch/powerpc] Error 2
  make[1]: *** Waiting for unfinished jobs....
  make: *** [Makefile:219: __sub-make] Error 2

cheers