bnxt_en: Fix first buffer size calculations for XDP multi-buffer

The size of the first buffer is always page size, and the useable
space is the page size minus the offset and the skb_shared_info size.
Make sure SKB and XDP buf sizes match so that the skb_shared_info
is at the same offset seen from the SKB and XDP_BUF.

build_skb() should be passed PAGE_SIZE.  xdp_init_buff() should
be passed PAGE_SIZE as well.  xdp_get_shared_info_from_buff() will
automatically deduct the skb_shared_info size if the XDP buffer
has frags.  There is no need to keep bp->xdp_has_frags.

Change BNXT_PAGE_MODE_BUF_SIZE to BNXT_MAX_PAGE_MODE_MTU_SBUF
since this constant is really the MTU with ethernet header size
subtracted.

Also fix the BNXT_MAX_PAGE_MODE_MTU macro with proper parentheses.

Fixes: 3286123 ("bnxt: change receive ring space parameters")
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -991,8 +991,7 @@ static struct sk_buff *bnxt_rx_multi_page_skb(struct bnxt *bp,
 	dma_addr -= bp->rx_dma_offset;
 	dma_unmap_page_attrs(&bp->pdev->dev, dma_addr, PAGE_SIZE, bp->rx_dir,
 			     DMA_ATTR_WEAK_ORDERING);
-	skb = build_skb(page_address(page), BNXT_PAGE_MODE_BUF_SIZE +
-					    bp->rx_dma_offset);
+	skb = build_skb(page_address(page), PAGE_SIZE);
 	if (!skb) {
 		__free_page(page);
 		return NULL;
@@ -3969,8 +3968,10 @@ void bnxt_set_ring_params(struct bnxt *bp)
 		bp->rx_agg_ring_mask = (bp->rx_agg_nr_pages * RX_DESC_CNT) - 1;
 
 		if (BNXT_RX_PAGE_MODE(bp)) {
-			rx_space = BNXT_PAGE_MODE_BUF_SIZE;
-			rx_size = BNXT_MAX_PAGE_MODE_MTU;
+			rx_space = PAGE_SIZE;
+			rx_size = PAGE_SIZE -
+				  ALIGN(max(NET_SKB_PAD, XDP_PACKET_HEADROOM), 8) -
+				  SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 		} else {
 			rx_size = SKB_DATA_ALIGN(BNXT_RX_COPY_THRESH + NET_IP_ALIGN);
 			rx_space = rx_size + NET_SKB_PAD +

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

@@ -591,12 +591,20 @@ struct nqe_cn {
 #define BNXT_RX_PAGE_SIZE (1 << BNXT_RX_PAGE_SHIFT)
 
 #define BNXT_MAX_MTU		9500
-#define BNXT_PAGE_MODE_BUF_SIZE \
+
+/* First RX buffer page in XDP multi-buf mode
+ *
+ * +-------------------------------------------------------------------------+
+ * | XDP_PACKET_HEADROOM | bp->rx_buf_use_size              | skb_shared_info|
+ * | (bp->rx_dma_offset) |                                  |                |
+ * +-------------------------------------------------------------------------+
+ */
+#define BNXT_MAX_PAGE_MODE_MTU_SBUF \
 	((unsigned int)PAGE_SIZE - VLAN_ETH_HLEN - NET_IP_ALIGN -	\
 	 XDP_PACKET_HEADROOM)
 #define BNXT_MAX_PAGE_MODE_MTU	\
-	BNXT_PAGE_MODE_BUF_SIZE - \
-	SKB_DATA_ALIGN((unsigned int)sizeof(struct skb_shared_info))
+	(BNXT_MAX_PAGE_MODE_MTU_SBUF - \
+	 SKB_DATA_ALIGN((unsigned int)sizeof(struct skb_shared_info)))
 
 #define BNXT_MIN_PKT_SIZE	52
 
@@ -2134,7 +2142,6 @@ 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

@@ -193,9 +193,6 @@ 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);
 
-	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);
 }
@@ -404,10 +401,8 @@ 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)