From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Puranjay Mohan" <puranjay@kernel.org>, <bpf@vger.kernel.org>
Cc: "Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Martin KaFai Lau" <martin.lau@linux.dev>,
"Eduard Zingerman" <eddyz87@gmail.com>,
"Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
"Song Liu" <song@kernel.org>,
"Yonghong Song" <yonghong.song@linux.dev>
Subject: Re: [PATCH bpf-next 1/2] bpf, x86: Support fetching AND/OR/XOR atomics in arena
Date: Wed, 23 Sep 2026 22:10:02 +0000 [thread overview]
Message-ID: <DLN1FMQGC8YJ.J9N5XFXJYJM8@gmail.com> (raw)
In-Reply-To: <20260923165301.3463007-2-puranjay@kernel.org>
On Wed, Sep 23, 2026 at 09:52 AM Puranjay Mohan <puranjay@kernel.org> wrote:
> + branch_target = prog;
> +
> + /* Load old value */
> + fault[0] = prog;
> + if (index_reg < 0)
> + emit_ldx(&prog, BPF_SIZE(insn->code), BPF_REG_0, dst_reg, insn->off);
> + else
> + emit_ldx_index(&prog, BPF_SIZE(insn->code), BPF_REG_0, dst_reg,
> + index_reg, insn->off);
can we drop the load in the arena case ?
lock cmpxchg puts the current value into rax when it fails,
so the loop can start with whatever R0 has in rax.
Then cmpxchg is the only insn that can fault and there is
no need for the 2nd extable entry and num_exentries++
in bpf_int_jit_compile().
next prev parent reply other threads:[~2026-09-23 22:10 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-23 16:52 [PATCH bpf-next 0/2] bpf, x86: Support fetching AND/OR/XOR atomics in arena Puranjay Mohan
2026-09-23 16:52 ` [PATCH bpf-next 1/2] " Puranjay Mohan
2026-09-23 18:03 ` bot+bpf-ci
2026-09-23 22:10 ` Alexei Starovoitov [this message]
2026-09-23 16:53 ` [PATCH bpf-next 2/2] selftests/bpf: Test " Puranjay Mohan
2026-09-23 22:11 ` Alexei Starovoitov
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