nfp: Add XDP frame size to netronome driver

The netronome nfp driver use PAGE_SIZE when xdp_prog is set, but
xdp.data_hard_start begins at offset NFP_NET_RX_BUF_HEADROOM.
Thus, adjust for this when setting xdp.frame_sz, as it counts
from data_hard_start.

When doing XDP_TX this driver is smart and instead of a full DMA-map
does a DMA-sync on with packet length. As xdp_adjust_tail can now
grow packet length, add checks to make sure that grow size is within
the DMA-mapped size.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/bpf/158945342911.97035.11214251236208648808.stgit@firesoul

drivers/net/ethernet/netronome/nfp/nfp_net_common.c

@@ -1741,10 +1741,15 @@ nfp_net_tx_xdp_buf(struct nfp_net_dp *dp, struct nfp_net_rx_ring *rx_ring,
 		   struct nfp_net_rx_buf *rxbuf, unsigned int dma_off,
 		   unsigned int pkt_len, bool *completed)
 {
+	unsigned int dma_map_sz = dp->fl_bufsz - NFP_NET_RX_BUF_NON_DATA;
 	struct nfp_net_tx_buf *txbuf;
 	struct nfp_net_tx_desc *txd;
 	int wr_idx;
 
+	/* Reject if xdp_adjust_tail grow packet beyond DMA area */
+	if (pkt_len + dma_off > dma_map_sz)
+		return false;
+
 	if (unlikely(nfp_net_tx_full(tx_ring, 1))) {
 		if (!*completed) {
 			nfp_net_xdp_complete(tx_ring);
@@ -1817,6 +1822,7 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget)
 	rcu_read_lock();
 	xdp_prog = READ_ONCE(dp->xdp_prog);
 	true_bufsz = xdp_prog ? PAGE_SIZE : dp->fl_bufsz;
+	xdp.frame_sz = PAGE_SIZE - NFP_NET_RX_BUF_HEADROOM;
 	xdp.rxq = &rx_ring->xdp_rxq;
 	tx_ring = r_vec->xdp_ring;