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

From: Greg KH <gregkh@linuxfoundation.org>
To: Conor Dooley <conor.dooley@microchip.com>
Cc: Minda Chen <minda.chen@starfivetech.com>,
	Conor Dooley <conor@kernel.org>,
	Jisheng Zhang <jszhang@kernel.org>,
	Samuel Holland <samuel@sholland.org>, Dao Lu <daolu@rivosinc.com>,
	Heiko Stuebner <heiko@sntech.de>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
	Mason Huo <mason.huo@starfivetech.com>,
	stable@vger.kernel.org
Subject: Re: [PATCH v1] riscv: Using TOOLCHAIN_HAS_ZIHINTPAUSE marco replace zihintpause
Date: Wed, 2 Aug 2023 11:42:59 +0200	[thread overview]
Message-ID: <2023080255-stomp-smell-43ae@gregkh> (raw)
In-Reply-To: <20230802-decibel-unshaved-fde1cfba2d20@wendy>

On Wed, Aug 02, 2023 at 09:52:45AM +0100, Conor Dooley wrote:
> 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@starfivetech.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@microchip.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?

Yes.

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