linux-kernel - Re: [PATCH v1] riscv: Using TOOLCHAIN_HAS_ZIHINTPAUSE marco replace zihintpause

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Message-ID: <20230802-seismic-gallstone-fca0f4b17076@wendy>
Date:   Wed, 2 Aug 2023 08:48:36 +0100
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Minda Chen <minda.chen@...rfivetech.com>
CC:     Conor Dooley <conor@...nel.org>,
        Jisheng Zhang <jszhang@...nel.org>,
        Samuel Holland <samuel@...lland.org>,
        Dao Lu <daolu@...osinc.com>, Heiko Stuebner <heiko@...ech.de>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        <linux-kernel@...r.kernel.org>, <linux-riscv@...ts.infradead.org>,
        Mason Huo <mason.huo@...rfivetech.com>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH v1] riscv: Using TOOLCHAIN_HAS_ZIHINTPAUSE marco replace
 zihintpause

On Wed, Aug 02, 2023 at 03:32:15PM +0800, Minda Chen wrote:
> 
> 
> On 2023/8/2 14:54, Conor Dooley wrote:
> > Hey Minda,
> > 
> > On Wed, Aug 02, 2023 at 02:42:15PM +0800, Minda Chen wrote:
> >> Actually it is a part of Conor's
> >> commit aae538cd03bc ("riscv: fix detection of toolchain
> >> Zihintpause support").
> >> It is looks like a merge issue.
> > 
> > Yup, spot on.
> > 
> >> Samuel's
> >> commit 0b1d60d6dd9e ("riscv: Fix build with
> >> CONFIG_CC_OPTIMIZE_FOR_SIZE=y") do not base on Conor's commit and
> >> revert to __riscv_zihintpause. So this patch can fix it.
> >> 
> >> Signed-off-by: Minda Chen <minda.chen@...rfivetech.com>
> > 
> > Did you actually manage to trigger this, or was this by inspection?
> > clang-15 + binutils 2.35 was, IIRC, how we spotted this because that's
> > what the clang-built-linux CI uses to test the LTS kernels from before
> > LLVM's IAS was supported for RISC-V. Seemingly all that needs to be
> > satisfied there is that zihintpause doesn't appear in -march so this has
> > gone unnoticed.
> > 
> > Fixes: 3c349eacc559 ("Merge patch "riscv: Fix build with CONFIG_CC_OPTIMIZE_FOR_SIZE=y"")
> > Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>
> > 
> > Thanks,
> > Conor.
> > 
> Thanks, Conor. I found this just by inspection. I found a issue that vdso.so call cpu_relax
> cause application core dump in kernel 6.1.31. I need Samuel'patch to fix this. And I search the log
> of processor.h found this issue.

That doesn't look like it is fixed in later stable kernels (we are at
6.1.42-rcN right now I think). It sounds we should ask Greg to backport
0b1d60d6dd9e ("riscv: Fix build with CONFIG_CC_OPTIMIZE_FOR_SIZE=y")
to 6.1. Does that make sense to you?

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