[RFC PATCH 4/6] powerpc/64s: Make hash MMU code build configurable

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of August 28, 2021 7:59 pm:
> 
> 
> Le 27/08/2021 à 18:34, Nicholas Piggin a écrit :
>> Introduce a new option CONFIG_PPC_64S_HASH_MMU which allows the 64s hash
>> MMU code to be compiled out if radix is selected and the minimum
>> supported CPU type is POWER9 or higher, and KVM is not selected.
>> 
>> This saves 128kB kernel image size (90kB text) on powernv_defconfig
>> minus KVM, 350kB on pseries_defconfig minus KVM, 40kB on a tiny config.
>> 
>> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
>> ---
>>   arch/powerpc/Kconfig                          |  1 +
>>   arch/powerpc/include/asm/book3s/64/mmu.h      | 22 +++++-
>>   .../include/asm/book3s/64/tlbflush-hash.h     |  7 ++
>>   arch/powerpc/include/asm/book3s/pgtable.h     |  4 ++
>>   arch/powerpc/include/asm/mmu.h                | 38 +++++++++--
>>   arch/powerpc/include/asm/mmu_context.h        |  2 +
>>   arch/powerpc/include/asm/paca.h               |  8 +++
>>   arch/powerpc/kernel/asm-offsets.c             |  2 +
>>   arch/powerpc/kernel/dt_cpu_ftrs.c             | 10 ++-
>>   arch/powerpc/kernel/entry_64.S                |  4 +-
>>   arch/powerpc/kernel/exceptions-64s.S          | 16 +++++
>>   arch/powerpc/kernel/mce.c                     |  2 +-
>>   arch/powerpc/kernel/mce_power.c               | 10 ++-
>>   arch/powerpc/kernel/paca.c                    | 18 ++---
>>   arch/powerpc/kernel/process.c                 | 13 ++--
>>   arch/powerpc/kernel/prom.c                    |  2 +
>>   arch/powerpc/kernel/setup_64.c                |  4 ++
>>   arch/powerpc/kexec/core_64.c                  |  4 +-
>>   arch/powerpc/kexec/ranges.c                   |  4 ++
>>   arch/powerpc/kvm/Kconfig                      |  1 +
>>   arch/powerpc/mm/book3s64/Makefile             | 17 +++--
>>   arch/powerpc/mm/book3s64/hash_pgtable.c       |  1 -
>>   arch/powerpc/mm/book3s64/hash_utils.c         | 10 ---
>>   .../{hash_hugetlbpage.c => hugetlbpage.c}     |  6 ++
>>   arch/powerpc/mm/book3s64/mmu_context.c        | 16 +++++
>>   arch/powerpc/mm/book3s64/pgtable.c            | 22 +++++-
>>   arch/powerpc/mm/book3s64/radix_pgtable.c      |  4 ++
>>   arch/powerpc/mm/book3s64/slb.c                | 16 -----
>>   arch/powerpc/mm/copro_fault.c                 |  2 +
>>   arch/powerpc/mm/fault.c                       | 17 +++++
>>   arch/powerpc/mm/pgtable.c                     | 10 ++-
>>   arch/powerpc/platforms/Kconfig.cputype        | 20 +++++-
>>   arch/powerpc/platforms/cell/Kconfig           |  1 +
>>   arch/powerpc/platforms/maple/Kconfig          |  1 +
>>   arch/powerpc/platforms/microwatt/Kconfig      |  2 +-
>>   arch/powerpc/platforms/pasemi/Kconfig         |  1 +
>>   arch/powerpc/platforms/powermac/Kconfig       |  1 +
>>   arch/powerpc/platforms/powernv/Kconfig        |  2 +-
>>   arch/powerpc/platforms/powernv/idle.c         |  2 +
>>   arch/powerpc/platforms/powernv/setup.c        |  2 +
>>   arch/powerpc/platforms/pseries/lpar.c         | 68 ++++++++++---------
>>   arch/powerpc/platforms/pseries/lparcfg.c      |  2 +-
>>   arch/powerpc/platforms/pseries/mobility.c     |  6 ++
>>   arch/powerpc/platforms/pseries/ras.c          |  4 ++
>>   arch/powerpc/platforms/pseries/reconfig.c     |  2 +
>>   arch/powerpc/platforms/pseries/setup.c        |  6 +-
>>   arch/powerpc/xmon/xmon.c                      |  8 ++-
>>   47 files changed, 310 insertions(+), 111 deletions(-)
>>   rename arch/powerpc/mm/book3s64/{hash_hugetlbpage.c => hugetlbpage.c} (95%)
> 
> Whaou ! Huge patch.
> 
> Several places you should be able to use IS_ENABLED() or simply radix_enabled() instead of #ifdefs 
> and rely on GCC to opt out stuff when radix_enabled() folds into 'true'.

A lot of it couldn't be done because of data structures but I'm sure I 
missed a lot. I will go over it again.

> I may do more detailed comments later when I have time.

Very much appreciated, but let me send out another version before you
get the fine toothed comb out so I don't waste too much of your time.
If there are no objections to the idea from a high level.

Thanks,
Nick