netdev - Re: [PATCH bpf-next v2] bpf: Allow XDP dev-bound programs to perform XDP

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Message-ID: <aAqevLQfeOoL9ikV@lore-rh-laptop>
Date: Thu, 24 Apr 2025 22:27:40 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	John Fastabend <john.fastabend@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Eduard Zingerman <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>,
	"David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
	bpf@...r.kernel.org, netdev@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v2] bpf: Allow XDP dev-bound programs to perform
 XDP_REDIRECT into maps

On Apr 23, Martin KaFai Lau wrote:
> On 4/23/25 10:44 AM, Lorenzo Bianconi wrote:
> > In the current implementation if the program is dev-bound to a specific
> > device, it will not be possible to perform XDP_REDIRECT into a DEVMAP
> > or CPUMAP even if the program is running in the driver NAPI context and
> > it is not attached to any map entry. This seems in contrast with the
> > explanation available in bpf_prog_map_compatible routine.
> > Fix the issue introducing __bpf_prog_map_compatible utility routine in
> > order to avoid bpf_prog_is_dev_bound() check running bpf_check_tail_call()
> > at program load time (bpf_prog_select_runtime()).
> > Continue forbidding to attach a dev-bound program to XDP maps
> > (BPF_MAP_TYPE_PROG_ARRAY, BPF_MAP_TYPE_DEVMAP and BPF_MAP_TYPE_CPUMAP).
> > 
> > Fixes: 3d76a4d3d4e59 ("bpf: XDP metadata RX kfuncs")
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> > Changes in v2:
> > - Introduce __bpf_prog_map_compatible() utility routine in order to skip
> >    bpf_prog_is_dev_bound check in bpf_check_tail_call()
> > - Extend xdp_metadata selftest
> > - Link to v1: https://lore.kernel.org/r/20250422-xdp-prog-bound-fix-v1-1-0b581fa186fe@kernel.org
> > ---
> >   kernel/bpf/core.c                                  | 27 +++++++++++++---------
> >   .../selftests/bpf/prog_tests/xdp_metadata.c        | 22 +++++++++++++++++-
> >   tools/testing/selftests/bpf/progs/xdp_metadata.c   | 13 +++++++++++
> 
> The change lgtm. Please separate the selftest changes to patch 2. Thanks.

ack, I will do in v3.

Regards,
Lorenzo

> 
> pw-bot: cr
> 

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