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Subject: Re: [PATCH v4] netdev attribute to control xdpgeneric skb
 linearization
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
        Luigi Rizzo <lrizzo@google.com>,
        Network Development <netdev@vger.kernel.org>,
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        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
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From:   Daniel Borkmann <daniel@iogearbox.net>
Message-ID: <abe8f703-d239-2444-99a0-c94dd53f478a@iogearbox.net>
Date:   Tue, 3 Mar 2020 22:04:55 +0100
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On 3/3/20 9:50 PM, Jakub Kicinski wrote:
> 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?

Yeah, agree, I'm curious about that part as well.

Thanks,
Daniel