netdev - Re: [PATCH RFC 2/9] veth: Add driver XDP

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Message-ID: <faba5cf5-8659-e953-d828-ad1f472ac0c9@lab.ntt.co.jp>
Date:   Thu, 26 Apr 2018 19:46:26 +0900
From:   Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Toshiaki Makita <toshiaki.makita1@...il.com>,
        netdev@...r.kernel.org
Subject: Re: [PATCH RFC 2/9] veth: Add driver XDP

Hi Jesper,

Thanks for taking a look!

On 2018/04/26 5:39, Jesper Dangaard Brouer wrote:
> On Tue, 24 Apr 2018 23:39:16 +0900
> Toshiaki Makita <toshiaki.makita1@...il.com> wrote:
> 
>> This is basic implementation of veth driver XDP.
>>
>> Incoming packets are sent from the peer veth device in the form of skb,
>> so this is generally doing the same thing as generic XDP.
> 
> I'm unsure that context you are calling veth_xdp_rcv_skb() from.  The
> XDP (RX side) depend heavily on the protection provided by NAPI context.
> It looks like you are adding NAPI handler later.  

This is called from softirq or bh disabled context.
I can see XDP REDIRECT depends on NAPI since it uses per-cpu temporary
storage which is used in ndo_xdp_flush. I thought DROP and PASS is safe
here. Also this is basically the same context as generic XDP, which is
called from netif_rx_internal.

Anyway this is a temporary state and not needed. It looks like this does
not help review so I'll squash this and patch 4 (napi patch).

-- 
Toshiaki Makita