Re: [PATCH] riscv: enable HAVE_CMPXCHG_{DOUBLE,LOCAL}

[Miquel Sabaté Solà]

Miquel Sabaté Solà @ 2026-03-11 09:17 +01:

> Miquel Sabaté Solà @ 2026-02-20 08:44 +01:
>
>> Support for atomic Compare-And-Swap instructions has been in the RISC-V
>> port of the Linux kernel for a long time. That being said, we apparently
>> never bothered to set HAVE_CMPXCHG_DOUBLE and HAVE_CMPXCHG_LOCAL in the
>> Kconfig, despite having all the framework to support them.
>>
>> Signed-off-by: Miquel Sabaté Solà <mssola@xxxxxxxxxx>
>> ---
>> I have built this patch with multiple configurations and ran it with KVM
>> (the VisionFive2 board that I have lacks the needed extensions). All seems
>> to work, but I do wonder if we did not enable these for a reason or this
>> just slipped through. So far in the code I believe everything is in place,
>> and I haven't seen any commit in the git log stating otherwise.
>>
>>  Documentation/features/locking/cmpxchg-local/arch-support.txt | 2 +-
>>  arch/riscv/Kconfig                                            | 2 ++
>>  2 files changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/features/locking/cmpxchg-local/arch-support.txt b/Documentation/features/locking/cmpxchg-local/arch-support.txt
>> index 2c3a4b91f16d..28d5fa8c3b4f 100644
>> --- a/Documentation/features/locking/cmpxchg-local/arch-support.txt
>> +++ b/Documentation/features/locking/cmpxchg-local/arch-support.txt
>> @@ -20,7 +20,7 @@
>>      |    openrisc: | TODO |
>>      |      parisc: | TODO |
>>      |     powerpc: | TODO |
>> -    |       riscv: | TODO |
>> +    |       riscv: |  ok  |
>>      |        s390: |  ok  |
>>      |          sh: | TODO |
>>      |       sparc: | TODO |
>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> index 7e76b6316425..7c6726a8d738 100644
>> --- a/arch/riscv/Kconfig
>> +++ b/arch/riscv/Kconfig
>> @@ -151,6 +151,8 @@ config RISCV
>>  	select HAVE_ARCH_USERFAULTFD_WP if 64BIT && MMU && USERFAULTFD && RISCV_ISA_SVRSW60T59B
>>  	select HAVE_ARCH_VMAP_STACK if MMU && 64BIT
>>  	select HAVE_ASM_MODVERSIONS
>> +	select HAVE_CMPXCHG_DOUBLE if RISCV_ISA_ZACAS && RISCV_ISA_ZABHA
>> +	select HAVE_CMPXCHG_LOCAL if RISCV_ISA_ZACAS && RISCV_ISA_ZABHA
>>  	select HAVE_CONTEXT_TRACKING_USER
>>  	select HAVE_DEBUG_KMEMLEAK
>>  	select HAVE_DMA_CONTIGUOUS if MMU
>
> Gentle ping :)

Another gentle ping :)

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