linux-kernel - Re: [PATCH bpf-next v12 0/7] bpf: Introduce BPF_F_CPU and BPF_F_ALL

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Message-ID: <CAADnVQLisw1HFdDKWvSyWGdpVE1wSUdUBB=5aE7srHjsLNELPg@mail.gmail.com>
Date: Tue, 6 Jan 2026 10:25:33 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Leon Hwang <leon.hwang@...ux.dev>
Cc: bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, 
	Andrii Nakryiko <andrii@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Jiri Olsa <jolsa@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, Song Liu <song@...nel.org>, Eduard <eddyz87@...il.com>, 
	Daniel Xu <dxu@...uu.xyz>, Daniel Müller <deso@...teo.net>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Shuah Khan <shuah@...nel.org>, Jason Xing <kerneljasonxing@...il.com>, 
	Tao Chen <chen.dylane@...ux.dev>, Willem de Bruijn <willemb@...gle.com>, 
	Paul Chaignon <paul.chaignon@...il.com>, Anton Protopopov <a.s.protopopov@...il.com>, 
	Kumar Kartikeya Dwivedi <memxor@...il.com>, Mykyta Yatsenko <yatsenko@...a.com>, 
	Tobias Klauser <tklauser@...tanz.ch>, kernel-patches-bot@...com, 
	LKML <linux-kernel@...r.kernel.org>, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH bpf-next v12 0/7] bpf: Introduce BPF_F_CPU and
 BPF_F_ALL_CPUS flags for percpu maps

On Wed, Nov 26, 2025 at 6:51 AM Leon Hwang <leon.hwang@...ux.dev> wrote:
>
> This patch set introduces the BPF_F_CPU and BPF_F_ALL_CPUS flags for
> percpu maps, as the requirement of BPF_F_ALL_CPUS flag for percpu_array
> maps was discussed in the thread of
> "[PATCH bpf-next v3 0/4] bpf: Introduce global percpu data"[1].
>
> The goal of BPF_F_ALL_CPUS flag is to reduce data caching overhead in light
> skeletons by allowing a single value to be reused to update values across all
> CPUs. This avoids the M:N problem where M cached values are used to update a
> map on N CPUs kernel.
>
> The BPF_F_CPU flag is accompanied by *flags*-embedded cpu info, which
> specifies the target CPU for the operation:
>
> * For lookup operations: the flag field alongside cpu info enable querying
>   a value on the specified CPU.
> * For update operations: the flag field alongside cpu info enable
>   updating value for specified CPU.
>
> Links:
> [1] https://lore.kernel.org/bpf/20250526162146.24429-1-leon.hwang@linux.dev/
>
> Changes:
> v11 -> v12:
> * Dropped the v11 changes.
> * Stabilized the lru_percpu_hash map test by keeping an extra spare entry,
>   which can be used temporarily during updates to avoid unintended LRU
>   evictions.

Please rebase and resend.
This set got lost during holidays.