Re: [PATCH bpf V7 1/7] selftests/bpf: xdp_hw_metadata default disable bpf_printk

[Jesper Dangaard Brouer]

On 12/04/2023 00.42, Stanislav Fomichev wrote:
> On Sat, Apr 8, 2023 at 12:24 PM Jesper Dangaard Brouer
> <brouer@xxxxxxxxxx> 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@xxxxxxxxxx>
> > ---
> >   .../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@xxxxxxxxxxxxxx/