net: enetc: block concurrent XDP transmissions during ring reconfiguration

When testing the XDP_REDIRECT function on the LS1028A platform, we
found a very reproducible issue that the Tx frames can no longer be
sent out even if XDP_REDIRECT is turned off. Specifically, if there
is a lot of traffic on Rx direction, when XDP_REDIRECT is turned on,
the console may display some warnings like "timeout for tx ring #6
clear", and all redirected frames will be dropped, the detailed log
is as follows.

root@ls1028ardb:~# ./xdp-bench redirect eno0 eno2
Redirecting from eno0 (ifindex 3; driver fsl_enetc) to eno2 (ifindex 4; driver fsl_enetc)
[203.849809] fsl_enetc 0000:00:00.2 eno2: timeout for tx ring #5 clear
[204.006051] fsl_enetc 0000:00:00.2 eno2: timeout for tx ring #6 clear
[204.161944] fsl_enetc 0000:00:00.2 eno2: timeout for tx ring #7 clear
eno0->eno2     1420505 rx/s       1420590 err,drop/s      0 xmit/s
  xmit eno0->eno2    0 xmit/s     1420590 drop/s     0 drv_err/s     15.71 bulk-avg
eno0->eno2     1420484 rx/s       1420485 err,drop/s      0 xmit/s
  xmit eno0->eno2    0 xmit/s     1420485 drop/s     0 drv_err/s     15.71 bulk-avg

By analyzing the XDP_REDIRECT implementation of enetc driver, the
driver will reconfigure Tx and Rx BD rings when a bpf program is
installed or uninstalled, but there is no mechanisms to block the
redirected frames when enetc driver reconfigures rings. Similarly,
XDP_TX verdicts on received frames can also lead to frames being
enqueued in the Tx rings. Because XDP ignores the state set by the
netif_tx_wake_queue() API, so introduce the ENETC_TX_DOWN flag to
suppress transmission of XDP frames.

Fixes: c33bfaf91c4c ("net: enetc: set up XDP program under enetc_reconfigure()")
Cc: stable@vger.kernel.org
Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20241010092056.298128-3-wei.fang@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
index 56e59721ec7d5abc471afaf940fb76d5f5bd8154..482c44ed9d46889890bc8e8d3d7df40fe1e223ec 100644 (file)
--- a/drivers/net/ethernet/freescale/enetc/enetc.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc.c
@@ -902,6 +902,7 @@ static bool enetc_clean_tx_ring(struct enetc_bdr *tx_ring, int napi_budget)
 
        if (unlikely(tx_frm_cnt && netif_carrier_ok(ndev) &&
                     __netif_subqueue_stopped(ndev, tx_ring->index) &&
+                    !test_bit(ENETC_TX_DOWN, &priv->flags) &&
                     (enetc_bd_unused(tx_ring) >= ENETC_TXBDS_MAX_NEEDED))) {
                netif_wake_subqueue(ndev, tx_ring->index);
        }
@@ -1377,6 +1378,9 @@ int enetc_xdp_xmit(struct net_device *ndev, int num_frames,
        int xdp_tx_bd_cnt, i, k;
        int xdp_tx_frm_cnt = 0;
 
+       if (unlikely(test_bit(ENETC_TX_DOWN, &priv->flags)))
+               return -ENETDOWN;
+
        enetc_lock_mdio();
 
        tx_ring = priv->xdp_tx_ring[smp_processor_id()];
@@ -1602,6 +1606,12 @@ static int enetc_clean_rx_ring_xdp(struct enetc_bdr *rx_ring,
                        break;
                case XDP_TX:
                        tx_ring = priv->xdp_tx_ring[rx_ring->index];
+                       if (unlikely(test_bit(ENETC_TX_DOWN, &priv->flags))) {
+                               enetc_xdp_drop(rx_ring, orig_i, i);
+                               tx_ring->stats.xdp_tx_drops++;
+                               break;
+                       }
+
                        xdp_tx_bd_cnt = enetc_rx_swbd_to_xdp_tx_swbd(xdp_tx_arr,
                                                                     rx_ring,
                                                                     orig_i, i);
@@ -2463,6 +2473,8 @@ void enetc_start(struct net_device *ndev)
        enetc_enable_bdrs(priv);
 
        netif_tx_start_all_queues(ndev);
+
+       clear_bit(ENETC_TX_DOWN, &priv->flags);
 }
 EXPORT_SYMBOL_GPL(enetc_start);
 
@@ -2520,6 +2532,8 @@ void enetc_stop(struct net_device *ndev)
        struct enetc_ndev_priv *priv = netdev_priv(ndev);
        int i;
 
+       set_bit(ENETC_TX_DOWN, &priv->flags);
+
        netif_tx_stop_all_queues(ndev);
 
        enetc_disable_bdrs(priv);

diff --git a/drivers/net/ethernet/freescale/enetc/enetc.h b/drivers/net/ethernet/freescale/enetc/enetc.h
index 97524dfa234c7dd0f10811fa815cc7eb2f3cd9d7..fb7d98d577839991bb4058431824df60a410cb2f 100644 (file)
--- a/drivers/net/ethernet/freescale/enetc/enetc.h
+++ b/drivers/net/ethernet/freescale/enetc/enetc.h
@@ -325,6 +325,7 @@ enum enetc_active_offloads {
 
 enum enetc_flags_bit {
        ENETC_TX_ONESTEP_TSTAMP_IN_PROGRESS = 0,
+       ENETC_TX_DOWN,
 };
 
 /* interrupt coalescing modes */