linux-kernel - Re: [PATCH bpf V7 1/7] selftests/bpf: xdp_hw_metadata default disable bpf

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Message-ID: <402a3c73-d26d-3619-d69a-c90eb3f0e9ee@redhat.com>
Date:   Wed, 12 Apr 2023 12:54:45 +0200
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     brouer@...hat.com, bpf@...r.kernel.org,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        martin.lau@...nel.org, ast@...nel.org, daniel@...earbox.net,
        alexandr.lobakin@...el.com, larysa.zaremba@...el.com,
        xdp-hints@...-project.net, anthony.l.nguyen@...el.com,
        yoong.siang.song@...el.com, boon.leong.ong@...el.com,
        intel-wired-lan@...ts.osuosl.org, pabeni@...hat.com,
        jesse.brandeburg@...el.com, kuba@...nel.org, edumazet@...gle.com,
        john.fastabend@...il.com, hawk@...nel.org, davem@...emloft.net,
        tariqt@...dia.com, saeedm@...dia.com, leon@...nel.org,
        linux-rdma@...r.kernel.org
Subject: Re: [PATCH bpf V7 1/7] selftests/bpf: xdp_hw_metadata default disable
 bpf_printk


On 12/04/2023 00.42, Stanislav Fomichev wrote:
> On Sat, Apr 8, 2023 at 12:24 PM Jesper Dangaard Brouer
> <brouer@...hat.com> wrote:
>>
>> The tool xdp_hw_metadata can be used by driver developers
>> implementing XDP-hints kfuncs.  The tool transfers the
>> XDP-hints via metadata information to an AF_XDP userspace
>> process. When everything works the bpf_printk calls are
>> unncesssary.  Thus, disable bpf_printk by default, but
>> make it easy to reenable for driver developers to use
>> when debugging their driver implementation.
>>
>> This also converts bpf_printk "forwarding UDP:9091 to AF_XDP"
>> into a code comment.  The bpf_printk's that are important
>> to the driver developers is when bpf_xdp_adjust_meta fails.
>> The likely mistake from driver developers is expected to
>> be that they didn't implement XDP metadata adjust support.
>>
>> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
>> ---
>>   .../testing/selftests/bpf/progs/xdp_hw_metadata.c  |   16 ++++++++++++++--
>>   1 file changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c b/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
>> index 4c55b4d79d3d..980eb60d8e5b 100644
>> --- a/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
>> +++ b/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
>> @@ -5,6 +5,19 @@
>>   #include <bpf/bpf_helpers.h>
>>   #include <bpf/bpf_endian.h>
>>
>> +/* Per default below bpf_printk() calls are disabled.  Can be
>> + * reenabled manually for convenience by XDP-hints driver developer,
>> + * when troublshooting the drivers kfuncs implementation details.
>> + *
>> + * Remember BPF-prog bpf_printk info output can be access via:
>> + *  /sys/kernel/debug/tracing/trace_pipe
>> + */
>> +//#define DEBUG        1
>> +#ifndef DEBUG
>> +#undef  bpf_printk
>> +#define bpf_printk(fmt, ...) ({})
>> +#endif
> 
> Are you planning to eventually do somethike similar to what I've
> mentioned in [0]? If not, should I try to send a patch?

See next patch:
  - [PATCH bpf V7 2/7] selftests/bpf: Add counters to xdp_hw_metadata

where I add these counters :-)

> 
> 0: https://lore.kernel.org/netdev/CAKH8qBupRYEg+SPMTMb4h532GESG7P1QdaFJ-+zrbARVN9xrdA@mail.gmail.com/
>