From: Guenter Roeck <linux@roeck-us.net>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, netdev <netdev@vger.kernel.org>,
Eric Dumazet <edumazet@google.com>,
Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
Jason Wang <jasowang@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH net-next] virtio-net: restrict build_skb() use to some arches
Date: Tue, 20 Apr 2021 14:53:07 -0700 [thread overview]
Message-ID: <20210420215307.GA103196@roeck-us.net> (raw)
On Tue, Apr 20, 2021 at 01:01:44PM -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
>
> build_skb() is supposed to be followed by
> skb_reserve(skb, NET_IP_ALIGN), so that IP headers are word-aligned.
> (Best practice is to reserve NET_IP_ALIGN+NET_SKB_PAD, but the NET_SKB_PAD
> part is only a performance optimization if tunnel encaps are added.)
>
> Unfortunately virtio_net has not provisioned this reserve.
> We can only use build_skb() for arches where NET_IP_ALIGN == 0
>
> We might refine this later, with enough testing.
>
> Fixes: fb32856b16ad ("virtio-net: page_to_skb() use build_skb when there's sufficient tailroom")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: virtualization@lists.linux-foundation.org
Tested-by: Guenter Roeck <linux@roeck-us.net>
on alpha, sh4 (little endian).
Thanks!
Guenter
next reply other threads:[~2021-04-20 21:53 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 21:53 Guenter Roeck [this message]
-- strict thread matches above, loose matches on Subject: below --
2021-04-20 20:01 [PATCH net-next] virtio-net: restrict build_skb() use to some arches Eric Dumazet
2021-04-21 0:00 ` patchwork-bot+netdevbpf
2021-04-21 2:18 ` Jason Wang
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