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Date:   Wed, 30 Mar 2022 19:16:22 -0700 (PDT)
Subject:     Re: [PATCH 2/3] RISC-V: K210 defconfigs: Drop redundant MEMBARRIER=n
In-Reply-To: <d8a35bea-f4a0-b54d-9d2a-d1cc9b3d3e53@opensource.wdc.com>
CC:     linux-riscv@lists.infradead.org, Niklas.Cassel@wdc.com,
        Paul Walmsley <paul.walmsley@sifive.com>,
        aou@eecs.berkeley.edu, anup@brainfault.org,
        heinrich.schuchardt@canonical.com, atishp@atishpatra.org,
        mchitale@ventanamicro.com, alexandre.ghiti@canonical.com,
        axboe@kernel.dk, linux-kernel@vger.kernel.org
From:   Palmer Dabbelt <palmer@rivosinc.com>
To:     damien.lemoal@opensource.wdc.com
Message-ID: <mhng-5bb87384-f841-4793-8f1a-fabd5c13a181@palmer-ri-x1c9>
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On Wed, 30 Mar 2022 17:26:45 PDT (-0700), damien.lemoal@opensource.wdc.com wrote:
> On 3/31/22 08:47, Palmer Dabbelt wrote:
>> From: Palmer Dabbelt <palmer@rivosinc.com>
>>
>> As of 93917ad50972 ("RISC-V: Add support for restartable sequence") we
>> have support for restartable sequences, which default to enabled.  These
>> select MEMBARRIER, so disabling it is now redundant.
>>
>> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
>>
>> ---
>>
>> I'm not actually sure this is the right way to go: presumably the K210
>> defconfigs had MEMBARRIER=n for a reason (maybe just size?), so we might
>> actually want to move to RSEQ=n instead?  As usual: I don't test on the
>> K210, so I'm not exactly sure what the constraints are.
>
> Not sure either. It is like this now because I think this was the default
> at the time the config was created.
>
> Niklas,
>
> Can you test this please ?

Thanks.  I'm OK either way, I guess I'd learn towards turning on the 
features if they work/fit.  I'll hold off on merging this one for a bit, 
I don't see any rush (it's just a defconfig) and if what was there is 
broken then we can take it as a fix.  Otherwise it'll just get rolled up 
into the next round of these, which I'll hopefully remember to do 
earlier next time.

>
>> ---
>>  arch/riscv/configs/nommu_k210_defconfig        | 1 -
>>  arch/riscv/configs/nommu_k210_sdcard_defconfig | 1 -
>>  arch/riscv/configs/nommu_virt_defconfig        | 1 -
>>  3 files changed, 3 deletions(-)
>>
>> diff --git a/arch/riscv/configs/nommu_k210_defconfig b/arch/riscv/configs/nommu_k210_defconfig
>> index 3f42ed87dde8..2438fa39f8ae 100644
>> --- a/arch/riscv/configs/nommu_k210_defconfig
>> +++ b/arch/riscv/configs/nommu_k210_defconfig
>> @@ -21,7 +21,6 @@ CONFIG_CC_OPTIMIZE_FOR_SIZE=y
>>  # CONFIG_AIO is not set
>>  # CONFIG_IO_URING is not set
>>  # CONFIG_ADVISE_SYSCALLS is not set
>> -# CONFIG_MEMBARRIER is not set
>>  # CONFIG_KALLSYMS is not set
>>  CONFIG_EMBEDDED=y
>>  # CONFIG_VM_EVENT_COUNTERS is not set
>> diff --git a/arch/riscv/configs/nommu_k210_sdcard_defconfig b/arch/riscv/configs/nommu_k210_sdcard_defconfig
>> index af64b95e88cc..9a133e63ae5b 100644
>> --- a/arch/riscv/configs/nommu_k210_sdcard_defconfig
>> +++ b/arch/riscv/configs/nommu_k210_sdcard_defconfig
>> @@ -13,7 +13,6 @@ CONFIG_CC_OPTIMIZE_FOR_SIZE=y
>>  # CONFIG_AIO is not set
>>  # CONFIG_IO_URING is not set
>>  # CONFIG_ADVISE_SYSCALLS is not set
>> -# CONFIG_MEMBARRIER is not set
>>  # CONFIG_KALLSYMS is not set
>>  CONFIG_EMBEDDED=y
>>  # CONFIG_VM_EVENT_COUNTERS is not set
>> diff --git a/arch/riscv/configs/nommu_virt_defconfig b/arch/riscv/configs/nommu_virt_defconfig
>> index e1c9864b6237..5269fbb6b4fc 100644
>> --- a/arch/riscv/configs/nommu_virt_defconfig
>> +++ b/arch/riscv/configs/nommu_virt_defconfig
>> @@ -19,7 +19,6 @@ CONFIG_EXPERT=y
>>  # CONFIG_AIO is not set
>>  # CONFIG_IO_URING is not set
>>  # CONFIG_ADVISE_SYSCALLS is not set
>> -# CONFIG_MEMBARRIER is not set
>>  # CONFIG_KALLSYMS is not set
>>  # CONFIG_VM_EVENT_COUNTERS is not set
>>  # CONFIG_COMPAT_BRK is not set