ice: 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, ice_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: 2d4238f55697 ("ice: Add support for AF_XDP")
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.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/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
index 2388837..8fd8052 100644 (file)
--- a/drivers/net/ethernet/intel/ice/ice_xsk.c
+++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
@@ -428,17 +428,15 @@ static void ice_bump_ntc(struct ice_rx_ring *rx_ring)
 static struct sk_buff *
 ice_construct_skb_zc(struct ice_rx_ring *rx_ring, struct xdp_buff *xdp)
 {
-       unsigned int datasize_hard = xdp->data_end - xdp->data_hard_start;
        unsigned int metasize = xdp->data - xdp->data_meta;
        unsigned int datasize = xdp->data_end - xdp->data;
        struct sk_buff *skb;
 
-       skb = __napi_alloc_skb(&rx_ring->q_vector->napi, datasize_hard,
+       skb = __napi_alloc_skb(&rx_ring->q_vector->napi, datasize,
                               GFP_ATOMIC | __GFP_NOWARN);
        if (unlikely(!skb))
                return NULL;
 
-       skb_reserve(skb, xdp->data - xdp->data_hard_start);
        memcpy(__skb_put(skb, datasize), xdp->data, datasize);
        if (metasize)
                skb_metadata_set(skb, metasize);