bnxt_en: Use PAGE_SIZE to init buffer when multi buffer XDP is not in use

Using BNXT_PAGE_MODE_BUF_SIZE + offset as buffer length value is not
sufficient when running single buffer XDP programs doing redirect
operations. The stack will complain on missing skb tail room. Fix it
by using PAGE_SIZE when calling xdp_init_buff() for single buffer
programs.

Fixes: b231c3f3 ("bnxt: refactor bnxt_rx_xdp to separate xdp_init_buff/xdp_prepare_buff")
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Signed-off-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/broadcom/bnxt/bnxt.h

@@ -2130,6 +2130,7 @@ struct bnxt {
 #define BNXT_DUMP_CRASH		1
 
 	struct bpf_prog		*xdp_prog;
+	u8			xdp_has_frags;
 
 	struct bnxt_ptp_cfg	*ptp_cfg;
 	u8			ptp_all_rx_tstamp;

drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c

@@ -181,6 +181,7 @@ void bnxt_xdp_buff_init(struct bnxt *bp, struct bnxt_rx_ring_info *rxr,
 			struct xdp_buff *xdp)
 {
 	struct bnxt_sw_rx_bd *rx_buf;
+	u32 buflen = PAGE_SIZE;
 	struct pci_dev *pdev;
 	dma_addr_t mapping;
 	u32 offset;
@@ -192,7 +193,10 @@ void bnxt_xdp_buff_init(struct bnxt *bp, struct bnxt_rx_ring_info *rxr,
 	mapping = rx_buf->mapping - bp->rx_dma_offset;
 	dma_sync_single_for_cpu(&pdev->dev, mapping + offset, *len, bp->rx_dir);
 
-	xdp_init_buff(xdp, BNXT_PAGE_MODE_BUF_SIZE + offset, &rxr->xdp_rxq);
+	if (bp->xdp_has_frags)
+		buflen = BNXT_PAGE_MODE_BUF_SIZE + offset;
+
+	xdp_init_buff(xdp, buflen, &rxr->xdp_rxq);
 	xdp_prepare_buff(xdp, *data_ptr - offset, offset, *len, false);
 }
 
@@ -397,8 +401,10 @@ static int bnxt_xdp_set(struct bnxt *bp, struct bpf_prog *prog)
 		netdev_warn(dev, "ethtool rx/tx channels must be combined to support XDP.\n");
 		return -EOPNOTSUPP;
 	}
-	if (prog)
+	if (prog) {
 		tx_xdp = bp->rx_nr_rings;
+		bp->xdp_has_frags = prog->aux->xdp_has_frags;
+	}
 
 	tc = netdev_get_num_tc(dev);
 	if (!tc)