net: fec: tx processing does not call XDP APIs if budget is 0

According to the clarification [1] in the latest napi.rst, the tx
processing cannot call any XDP (or page pool) APIs if the "budget"
is 0. Because NAPI is called with the budget of 0 (such as netpoll)
indicates we may be in an IRQ context, however, we cannot use the
page pool from IRQ context.

[1] https://lore.kernel.org/all/20230720161323.2025379-1-kuba@kernel.org/

Fixes: 20f797399035 ("net: fec: recycle pages for transmitted XDP frames")
Signed-off-by: Wei Fang <wei.fang@nxp.com>
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20230725074148.2936402-1-wei.fang@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 073d616193363b64062baa49224265a96f5bcf96..66b5cbdb43b9e3cfd142d7d123aee141cab811fb 100644 (file)
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -1372,7 +1372,7 @@ fec_enet_hwtstamp(struct fec_enet_private *fep, unsigned ts,
 }
 
 static void
-fec_enet_tx_queue(struct net_device *ndev, u16 queue_id)
+fec_enet_tx_queue(struct net_device *ndev, u16 queue_id, int budget)
 {
        struct  fec_enet_private *fep;
        struct xdp_frame *xdpf;
@@ -1416,6 +1416,14 @@ fec_enet_tx_queue(struct net_device *ndev, u16 queue_id)
                        if (!skb)
                                goto tx_buf_done;
                } else {
+                       /* Tx processing cannot call any XDP (or page pool) APIs if
+                        * the "budget" is 0. Because NAPI is called with budget of
+                        * 0 (such as netpoll) indicates we may be in an IRQ context,
+                        * however, we can't use the page pool from IRQ context.
+                        */
+                       if (unlikely(!budget))
+                               break;
+
                        xdpf = txq->tx_buf[index].xdp;
                        if (bdp->cbd_bufaddr)
                                dma_unmap_single(&fep->pdev->dev,
@@ -1508,14 +1516,14 @@ tx_buf_done:
                writel(0, txq->bd.reg_desc_active);
 }
 
-static void fec_enet_tx(struct net_device *ndev)
+static void fec_enet_tx(struct net_device *ndev, int budget)
 {
        struct fec_enet_private *fep = netdev_priv(ndev);
        int i;
 
        /* Make sure that AVB queues are processed first. */
        for (i = fep->num_tx_queues - 1; i >= 0; i--)
-               fec_enet_tx_queue(ndev, i);
+               fec_enet_tx_queue(ndev, i, budget);
 }
 
 static void fec_enet_update_cbd(struct fec_enet_priv_rx_q *rxq,
@@ -1858,7 +1866,7 @@ static int fec_enet_rx_napi(struct napi_struct *napi, int budget)
 
        do {
                done += fec_enet_rx(ndev, budget - done);
-               fec_enet_tx(ndev);
+               fec_enet_tx(ndev, budget);
        } while ((done < budget) && fec_enet_collect_events(fep));
 
        if (done < budget) {