linux-kernel - [PATCH bpf-next v2] bpf: Allow to use kfunc XDP hints and frags together

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Date:   Fri, 15 Sep 2023 10:39:10 +0200
From:   Larysa Zaremba <larysa.zaremba@...el.com>
To:     bpf@...r.kernel.org
Cc:     Larysa Zaremba <larysa.zaremba@...el.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        linux-kernel@...r.kernel.org,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Subject: [PATCH bpf-next v2] bpf: Allow to use kfunc XDP hints and frags together

There is no fundamental reason, why multi-buffer XDP and XDP kfunc RX hints
cannot coexist in a single program.

Allow those features to be used together by modifying the flags condition
for dev-bound-only programs, segments are still prohibited for fully
offloaded programs, hence additional check.

Suggested-by: Stanislav Fomichev <sdf@...gle.com>
Link: https://lore.kernel.org/bpf/CAKH8qBuzgtJj=OKMdsxEkyML36VsAuZpcrsXcyqjdKXSJCBq=Q@mail.gmail.com/
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Signed-off-by: Larysa Zaremba <larysa.zaremba@...el.com>
---
 kernel/bpf/offload.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index ee35f33a96d1..9d8e508c9b86 100644
--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -232,7 +232,14 @@ int bpf_prog_dev_bound_init(struct bpf_prog *prog, union bpf_attr *attr)
 	    attr->prog_type != BPF_PROG_TYPE_XDP)
 		return -EINVAL;
 
-	if (attr->prog_flags & ~BPF_F_XDP_DEV_BOUND_ONLY)
+	if (attr->prog_flags & ~(BPF_F_XDP_DEV_BOUND_ONLY | BPF_F_XDP_HAS_FRAGS))
+		return -EINVAL;
+
+	/* Frags are allowed only if program is dev-bound-only, but not
+	 * if it is requesting bpf offload.
+	 */
+	if (attr->prog_flags & BPF_F_XDP_HAS_FRAGS &&
+	    !(attr->prog_flags & BPF_F_XDP_DEV_BOUND_ONLY))
 		return -EINVAL;
 
 	if (attr->prog_type == BPF_PROG_TYPE_SCHED_CLS &&
-- 
2.41.0