linux-kernel - Re: [RFC PATCH bpf-next 6/8] sched_ext: Add filter for scx_kfunc_ids

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Message-ID: <CAADnVQJZnNj3KGcy-MKz_F2KEiKWGpXchxVx1zuGA-5g3SO=HQ@mail.gmail.com>
Date: Fri, 7 Feb 2025 19:37:51 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Juntong Deng <juntong.deng@...look.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	John Fastabend <john.fastabend@...il.com>, Andrii Nakryiko <andrii@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Eddy Z <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Kumar Kartikeya Dwivedi <memxor@...il.com>, Tejun Heo <tj@...nel.org>, David Vernet <void@...ifault.com>, 
	Andrea Righi <arighi@...dia.com>, changwoo@...lia.com, bpf <bpf@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH bpf-next 6/8] sched_ext: Add filter for scx_kfunc_ids_unlocked

On Wed, Feb 5, 2025 at 11:35 AM Juntong Deng <juntong.deng@...look.com> wrote:
>
> This patch adds filter for scx_kfunc_ids_unlocked.
>
> The kfuncs in the scx_kfunc_ids_unlocked set can be used in init, exit,
> cpu_online, cpu_offline, init_task, dump, cgroup_init, cgroup_exit,
> cgroup_prep_move, cgroup_cancel_move, cgroup_move, cgroup_set_weight
> operations.
>
> Signed-off-by: Juntong Deng <juntong.deng@...look.com>
> ---
>  kernel/sched/ext.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
>
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index 7f039a32f137..955fb0f5fc5e 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -7079,9 +7079,39 @@ BTF_ID_FLAGS(func, scx_bpf_dispatch_from_dsq, KF_RCU)
>  BTF_ID_FLAGS(func, scx_bpf_dispatch_vtime_from_dsq, KF_RCU)
>  BTF_KFUNCS_END(scx_kfunc_ids_unlocked)
>
> +static int scx_kfunc_ids_unlocked_filter(const struct bpf_prog *prog, u32 kfunc_id)
> +{
> +       u32 moff;
> +
> +       if (!btf_id_set8_contains(&scx_kfunc_ids_unlocked, kfunc_id) ||
> +           prog->aux->st_ops != &bpf_sched_ext_ops)
> +               return 0;
> +
> +       moff = prog->aux->attach_st_ops_member_off;
> +       if (moff == offsetof(struct sched_ext_ops, init) ||
> +           moff == offsetof(struct sched_ext_ops, exit) ||
> +           moff == offsetof(struct sched_ext_ops, cpu_online) ||
> +           moff == offsetof(struct sched_ext_ops, cpu_offline) ||
> +           moff == offsetof(struct sched_ext_ops, init_task) ||
> +           moff == offsetof(struct sched_ext_ops, dump))
> +               return 0;
> +
> +#ifdef CONFIG_EXT_GROUP_SCHED
> +       if (moff == offsetof(struct sched_ext_ops, cgroup_init) ||
> +           moff == offsetof(struct sched_ext_ops, cgroup_exit) ||
> +           moff == offsetof(struct sched_ext_ops, cgroup_prep_move) ||
> +           moff == offsetof(struct sched_ext_ops, cgroup_cancel_move) ||
> +           moff == offsetof(struct sched_ext_ops, cgroup_move) ||
> +           moff == offsetof(struct sched_ext_ops, cgroup_set_weight))
> +               return 0;
> +#endif
> +       return -EACCES;
> +}
> +
>  static const struct btf_kfunc_id_set scx_kfunc_set_unlocked = {
>         .owner                  = THIS_MODULE,
>         .set                    = &scx_kfunc_ids_unlocked,
> +       .filter                 = scx_kfunc_ids_unlocked_filter,
>  };

why does sched-ext use so many id_set-s ?

        if ((ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS,
                                             &scx_kfunc_set_select_cpu)) ||
            (ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS,

&scx_kfunc_set_enqueue_dispatch)) ||
            (ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS,
                                             &scx_kfunc_set_dispatch)) ||
            (ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS,
                                             &scx_kfunc_set_cpu_release)) ||
            (ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS,
                                             &scx_kfunc_set_unlocked)) ||

Can they all be rolled into one id_set then
the patches 2-6 will be collapsed into one patch and
one filter callback that will describe allowed hook/kfunc combinations?