Re: [PATCH net-next] virtio-net: restrict build_skb() use to some arches
From: Jason Wang <jasowang@redhat.com>
Date: 2021-04-21 02:18:59
Also in:
virtualization
在 2021/4/21 上午4:01, Eric Dumazet 写道:
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.orgAcked-by: Jason Wang <jasowang@redhat.com>
quoted hunk ↗ jump to hunk
--- 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;