From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: "Björn Töpel" <bjorn.topel@gmail.com>,
ast@kernel.org, daniel@iogearbox.net, bpf@vger.kernel.org,
john.fastabend@gmail.com
Cc: "Björn Töpel" <bjorn.topel@intel.com>,
magnus.karlsson@intel.com, netdev@vger.kernel.org,
brouer@redhat.com, maciej.fijalkowski@intel.com
Subject: Re: [RFC PATCH bpf-next 2/2] i40e: avoid xdp_do_redirect() call when "redirect_tail_call" is set
Date: Tue, 09 Jun 2020 21:47:46 +0200 [thread overview]
Message-ID: <87r1uo81i5.fsf@toke.dk> (raw)
In-Reply-To: <20200609172622.37990-3-bjorn.topel@gmail.com>
Björn Töpel <bjorn.topel@gmail.com> writes:
> From: Björn Töpel <bjorn.topel@intel.com>
>
> If an XDP program, where all the bpf_redirect_map() calls are tail
> calls (as defined by the previous commit), the driver does not need to
> explicitly call xdp_do_redirect().
>
> The driver checks the active XDP program, and notifies the BPF helper
> indirectly via xdp_set_redirect_tailcall().
>
> This is just a naive, as-simple-as-possible implementation, calling
> xdp_set_redirect_tailcall() for each packet.
Do you really need the driver changes? The initial setup could be moved
to bpf_prog_run_xdp(), and xdp_do_redirect() could be changed to an
inline wrapper that just checks a flag and immediately returns 0 if the
redirect action was already performed. Or am I missing some reason why
this wouldn't work?
-Toke
next prev parent reply other threads:[~2020-06-09 19:47 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-09 17:26 [RFC PATCH bpf-next 0/2] bpf_redirect_map() tail call detection and xdp_do_redirect() avoidance Björn Töpel
2020-06-09 17:26 ` [RFC PATCH bpf-next 1/2] bpf, xdp: add naive bpf_redirect_map() tail call detection Björn Töpel
2020-06-09 17:26 ` [RFC PATCH bpf-next 2/2] i40e: avoid xdp_do_redirect() call when "redirect_tail_call" is set Björn Töpel
2020-06-09 19:47 ` Toke Høiland-Jørgensen [this message]
2020-06-10 11:12 ` Björn Töpel
2020-06-09 20:10 ` [RFC PATCH bpf-next 0/2] bpf_redirect_map() tail call detection and xdp_do_redirect() avoidance Toke Høiland-Jørgensen
2020-06-10 12:21 ` Jesper Dangaard Brouer
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