i40e: don't reserve excessive XDP_PACKET_HEADROOM on XSK Rx to skb

{__,}napi_alloc_skb() allocates and reserves additional NET_SKB_PAD
+ NET_IP_ALIGN for any skb.
OTOH, i40e_construct_skb_zc() currently allocates and reserves
additional `xdp->data - xdp->data_hard_start`, which is
XDP_PACKET_HEADROOM for XSK frames.
There's no need for that at all as the frame is post-XDP and will
go only to the networking stack core.
Pass the size of the actual data only to __napi_alloc_skb() and
don't reserve anything. This will give enough headroom for stack
processing.

Fixes: 0a714186d3c0 ("i40e: add AF_XDP zero-copy Rx support")
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Tested-by: Kiran Bhandare <kiranx.bhandare@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

diff --git a/drivers/net/ethernet/intel/i40e/i40e_xsk.c b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
index 945b1bb9c6f40baac925d162db8f66ff4f662169..a449c84fe357c1b1cb52ca3127140725fa9c91df 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_xsk.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
@@ -246,13 +246,11 @@ static struct sk_buff *i40e_construct_skb_zc(struct i40e_ring *rx_ring,
        struct sk_buff *skb;
 
        /* allocate a skb to store the frags */
-       skb = __napi_alloc_skb(&rx_ring->q_vector->napi,
-                              xdp->data_end - xdp->data_hard_start,
+       skb = __napi_alloc_skb(&rx_ring->q_vector->napi, datasize,
                               GFP_ATOMIC | __GFP_NOWARN);
        if (unlikely(!skb))
                goto out;
 
-       skb_reserve(skb, xdp->data - xdp->data_hard_start);
        memcpy(__skb_put(skb, datasize), xdp->data, datasize);
        if (metasize)
                skb_metadata_set(skb, metasize);