linux-kernel - Re: [PATCH 2/3] RISC-V: K210 defconfigs: Drop redundant MEMBARRIER=n

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Message-ID: <YkeSLG3OdeknqJUR@x1-carbon>
Date:   Sat, 2 Apr 2022 00:00:46 +0000
From:   Niklas Cassel <Niklas.Cassel@....com>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
CC:     Palmer Dabbelt <palmer@...osinc.com>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        "aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
        "anup@...infault.org" <anup@...infault.org>,
        "heinrich.schuchardt@...onical.com" 
        <heinrich.schuchardt@...onical.com>,
        "atishp@...shpatra.org" <atishp@...shpatra.org>,
        "mchitale@...tanamicro.com" <mchitale@...tanamicro.com>,
        "alexandre.ghiti@...onical.com" <alexandre.ghiti@...onical.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] RISC-V: K210 defconfigs: Drop redundant MEMBARRIER=n

On Thu, Mar 31, 2022 at 09:26:45AM +0900, Damien Le Moal wrote:
> On 3/31/22 08:47, Palmer Dabbelt wrote:
> > From: Palmer Dabbelt <palmer@...osinc.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@...osinc.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 ?

Apologies for not being able to get back sooner.

I can see that this has already landed in Linus's tree:
a3dfc532b873 ("Merge tag 'riscv-for-linus-5.18-mw1' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux")

I smoke tested the above SHA1 on a k210 board, and on QEMU no-MMU
(since that defconfig was updated as well), and saw no issues.


Kind regards,
Niklas


> 
> > ---
> >  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
> 
> 
> -- 
> Damien Le Moal
> Western Digital Research