Re: [PATCH bpf-next v2 0/3] riscv, bpf: Fix signed operations and add 32 bit atomics - Kuan-Wei Chiu

From: Kuan-Wei Chiu <visitorckw@gmail.com>
To: Pu Lehui <pulehui@huawei.com>
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
	eddyz87@gmail.com, memxor@gmail.com, luke.r.nels@gmail.com,
	xi.wang@gmail.com, pjw@kernel.org, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, martin.lau@linux.dev, song@kernel.org,
	yonghong.song@linux.dev, jolsa@kernel.org, alex@ghiti.fr,
	jserv@ccns.ncku.edu.tw, eleanor15x@gmail.com,
	marscheng@google.com, bpf@vger.kernel.org,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf-next v2 0/3] riscv, bpf: Fix signed operations and add 32 bit atomics
Date: Tue, 16 Jun 2026 10:21:02 +0800	[thread overview]
Message-ID: <ajCzDo7bnUqE0DiW@google.com> (raw)
In-Reply-To: <216ee1df-2945-4266-9c70-ebcd36faeb7f@huawei.com>

Hi Lehui,

On Tue, Jun 16, 2026 at 09:41:21AM +0800, Pu Lehui wrote:
> 
> 
> On 2026/6/16 0:18, Kuan-Wei Chiu wrote:
> > Hi,
> > 
> > On Mon, May 11, 2026 at 10:16:45PM +0000, Kuan-Wei Chiu wrote:
> > > Fix miscompiled signed operations and expands 32 bit atomic support in
> > > the RV32 BPF JIT.
> > > 
> > > The current implementation ignores the instruction offset field used by
> > > the bpf instruction set to specify BPF_SDIV/BPF_SMOD and BPF_MOVSX.
> > > This causes these operations to be treated as unsigned or
> > > zero-extended, leading to test_bpf failures. Fix this by checking the
> > > offset and emitting the correct instructions.
> > > 
> > > Additionally, we leverage the mandatory A extension to natively support
> > > 32 bit bpf atomics (and, or, xor, xchg) by mapping them directly to
> > > amo*.w instructions. BPF_CMPXCHG continues to fall back to the
> > > interpreter.
> > > 
> > > As a result, test_bpf.ko now runs with 0 failures, and the total number
> > > of successfully JIT'ed test cases increases from 843 to 902.
> > 
> > Is there anything else I need to do for this patchset to land?
> 
> Hi Kuan-wei, it seems Luke and Xi haven't been as active in the community
> for a while, I'll make time to cover the review and testing for this.

Thank you for stepping in to help with the review and testing.
I really appreciate it.

Since Luke and Xi haven't been active for a while, I was wondering if
we should consider updating the MAINTAINERS file to reflect the current
status?

Also, if you need extra hands, I'd be glad to help review and test
future RV32 BPF patches.

Regards,
Kuan-Wei

> 
> Regards,
> Lehui
> 
> > 
> > Regards,
> > Kuan-wei
> > 
> > > ---
> > > - Add missing Fixes tags.
> > > - Fix memory ordering by emitting aq=1, rl=1
> > > 
> > > Kuan-Wei Chiu (3):
> > >    riscv, bpf: Fix support for BPF_SDIV and BPF_SMOD in RV32 JIT
> > >    riscv, bpf: Fix support for BPF_MOVSX in RV32 JIT
> > >    riscv, bpf: Add 32 bit atomic operations to RV32 JIT
> > > 
> > >   arch/riscv/net/bpf_jit_comp32.c | 101 +++++++++++++++++++++++++++-----
> > >   1 file changed, 85 insertions(+), 16 deletions(-)
> > > 
> > > -- 
> > > 2.54.0.563.g4f69b47b94-goog
> > > 
> > 
> > _______________________________________________
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