On Mon, 2013-03-25 at 12:59 -0400, David Miller wrote:

If this GRO packet ends up being transmitted, the gso limit should be
applied, otherwise we would be violating the device's advertised GSO
limit value.

Assume that this kind of check is performed (it must), then I don't
see how GRO can cause any problems for Xen.

It seems nobody cared to perform this generic check.

netif_skb_features() only deals with max_segs :

if (skb_shinfo(skb)->gso_segs > skb->dev->gso_max_segs) 
	features &= ~NETIF_F_GSO_MASK; 


dev->gso_max_size is currently only used to populate sk->sk_gso_max_size

For regular 1500 MTU and at most 17 frags per skb, its hardly a problem,
but it could happen with jumbo frames, or using loopback and splice()