Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 3 Mar 2020 12:50:20 -0800
From:   Jakub Kicinski <kuba@kernel.org>
To:     Daniel Borkmann <daniel@iogearbox.net>
Cc:     Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
        Luigi Rizzo <lrizzo@google.com>,
        Network Development <netdev@vger.kernel.org>,
        Toke =?UTF-8?B?SMO4aWxhbmQtSsO4cmdlbnNlbg==?= <toke@redhat.com>,
        David Miller <davem@davemloft.net>, hawk@kernel.org,
        "Jubran, Samih" <sameehj@amazon.com>,
        linux-kernel <linux-kernel@vger.kernel.org>, ast@kernel.org,
        bpf@vger.kernel.org
Subject: Re: [PATCH v4] netdev attribute to control xdpgeneric skb
 linearization
Message-ID: <20200303125020.2baef01b@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
In-Reply-To: <3c27d9c0-eb17-b20f-2d10-01f3bdf8c0d6@iogearbox.net>
References: <20200228105435.75298-1-lrizzo@google.com>
        <20200228110043.2771fddb@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
        <CA+FuTSfd80pZroxtqZDsTeEz4FaronC=pdgjeaBBfYqqi5HiyQ@mail.gmail.com>
        <3c27d9c0-eb17-b20f-2d10-01f3bdf8c0d6@iogearbox.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, 3 Mar 2020 20:46:55 +0100 Daniel Borkmann wrote:
> Thus, when the data/data_end test fails in generic XDP, the user can
> call e.g. bpf_xdp_pull_data(xdp, 64) to make sure we pull in as much as
> is needed w/o full linearization and once done the data/data_end can be
> repeated to proceed. Native XDP will leave xdp->rxq->skb as NULL, but
> later we could perhaps reuse the same bpf_xdp_pull_data() helper for
> native with skb-less backing. Thoughts?

I'm curious why we consider a xdpgeneric-only addition. Is attaching 
a cls_bpf program noticeably slower than xdpgeneric?