From: Eric Dumazet <eric.dumazet@gmail.com>
To: "David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>
Cc: netdev <netdev@vger.kernel.org>,
Eric Dumazet <edumazet@google.com>,
Eric Dumazet <eric.dumazet@gmail.com>,
Guenter Roeck <linux@roeck-us.net>,
Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
Jason Wang <jasowang@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
virtualization@lists.linux-foundation.org
Subject: [PATCH net-next] virtio-net: restrict build_skb() use to some arches
Date: Tue, 20 Apr 2021 13:01:44 -0700 [thread overview]
Message-ID: <20210420200144.4189597-1-eric.dumazet@gmail.com> (raw)
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
---
drivers/net/virtio_net.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 2e28c04aa6351d2b4016f7d277ce104c4970069d..74d2d49264f3f3b7039be70331d4a44c53b8cc28 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -416,7 +416,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
shinfo_size = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
- if (len > GOOD_COPY_LEN && tailroom >= shinfo_size) {
+ if (!NET_IP_ALIGN && len > GOOD_COPY_LEN && tailroom >= shinfo_size) {
skb = build_skb(p, truesize);
if (unlikely(!skb))
return NULL;
--
2.31.1.368.gbe11c130af-goog
next reply other threads:[~2021-04-20 20:01 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 20:01 Eric Dumazet [this message]
2021-04-21 0:00 ` [PATCH net-next] virtio-net: restrict build_skb() use to some arches patchwork-bot+netdevbpf
2021-04-21 2:18 ` Jason Wang
2021-04-20 21:53 Guenter Roeck
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