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

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Message-ID: <20230802-decibel-unshaved-fde1cfba2d20@wendy>
Date:   Wed, 2 Aug 2023 09:52:45 +0100
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     Minda Chen <minda.chen@...rfivetech.com>,
        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 10:33:27AM +0200, Greg KH wrote:
> On Wed, Aug 02, 2023 at 04:17:51PM +0800, Minda Chen wrote:
> > 
> > 
> > On 2023/8/2 15:48, Conor Dooley wrote:
> > > 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?
> > Yes. 6.1 is lts kernel. Starfive will use this kernel for a long time. Thanks.
> 
> What is preventing you from moving to a newer kernel version?  All of
> your kernel changes are already properly merged into Linus's tree,
> right?

Regardless of their reasons, "vdso.so call cpu_relax cause application
core dump" is something that we should fix in stable kernels, no?

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