[PATCH v2 1/2] igc: Fix race in igc_xdp_xmit_zc

[PATCH v2 1/2] igc: Fix race in igc_xdp_xmit_zc

[jeff.evanson]

From: Jeff Evanson <jeff.evanson@qsc.com>

In igc_xdp_xmit_zc, initialize next_to_use while holding the netif_tx_lock
to prevent racing with other users of the tx ring.

Fixes: 9acf59a752d4 (igc: Enable TX via AF_XDP zero-copy)
---
 drivers/net/ethernet/intel/igc/igc_main.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 1c00ee310c19..a36a18c84aeb 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -2598,7 +2598,7 @@ static void igc_xdp_xmit_zc(struct igc_ring *ring)
 	struct netdev_queue *nq = txring_txq(ring);
 	union igc_adv_tx_desc *tx_desc = NULL;
 	int cpu = smp_processor_id();
-	u16 ntu = ring->next_to_use;
+	u16 ntu;
 	struct xdp_desc xdp_desc;
 	u16 budget;
 
@@ -2607,6 +2607,8 @@ static void igc_xdp_xmit_zc(struct igc_ring *ring)
 
 	__netif_tx_lock(nq, cpu);
 
+	ntu = ring->next_to_use;
+
 	budget = igc_desc_unused(ring);
 
 	while (xsk_tx_peek_desc(pool, &xdp_desc) && budget--) {
-- 
2.17.1

[PATCH v2 2/2] igc: Trigger proper interrupts in igc_xsk_wakeup

[jeff.evanson]

From: Jeff Evanson <jeff.evanson@qsc.com>

In igc_xsk_wakeup, trigger the proper interrupt based on whether flags
contains XDP_WAKEUP_RX and/or XDP_WAKEUP_TX.

Consider a scenario where the transmit queue interrupt is mapped to a
different irq from the receive queue. If XDP_WAKEUP_TX is set in the
flags argument, the interrupt for transmit queue must be triggered,
otherwise the transmit queue's napi_struct will never be scheduled.

In the case where both XDP_WAKEUP_TX and XDP_WAKEUP_RX are both set,
the receive interrupt should always be triggered, but the transmit
interrupt should only be triggered if its q_vector differs from the
receive queue's interrupt.

Fixes: fc9df2a0b520 ("igc: Enable RX via AF_XDP zero-copy")
---
 drivers/net/ethernet/intel/igc/igc_main.c | 40 ++++++++++++++++++-----
 1 file changed, 31 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index a36a18c84aeb..41b5d1ac8bc1 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -6072,8 +6072,8 @@ static void igc_trigger_rxtxq_interrupt(struct igc_adapter *adapter,
 
 int igc_xsk_wakeup(struct net_device *dev, u32 queue_id, u32 flags)
 {
+	struct igc_q_vector *txq_vector = NULL, *rxq_vector = NULL;
 	struct igc_adapter *adapter = netdev_priv(dev);
-	struct igc_q_vector *q_vector;
 	struct igc_ring *ring;
 
 	if (test_bit(__IGC_DOWN, &adapter->state))
@@ -6082,17 +6082,39 @@ int igc_xsk_wakeup(struct net_device *dev, u32 queue_id, u32 flags)
 	if (!igc_xdp_is_enabled(adapter))
 		return -ENXIO;
 
-	if (queue_id >= adapter->num_rx_queues)
-		return -EINVAL;
+	if (flags & XDP_WAKEUP_RX) {
+		if (queue_id >= adapter->num_rx_queues)
+			return -EINVAL;
 
-	ring = adapter->rx_ring[queue_id];
+		ring = adapter->rx_ring[queue_id];
+		if (!ring->xsk_pool)
+			return -ENXIO;
 
-	if (!ring->xsk_pool)
-		return -ENXIO;
+		rxq_vector = ring->q_vector;
+	}
+
+	if (flags & XDP_WAKEUP_TX) {
+		if (queue_id >= adapter->num_tx_queues)
+			return -EINVAL;
+
+		ring = adapter->tx_ring[queue_id];
+		if (!ring->xsk_pool)
+			return -ENXIO;
+
+		txq_vector = ring->q_vector;
+	}
+
+	if (rxq_vector != NULL &&
+	    !napi_if_scheduled_mark_missed(&rxq_vector->napi))
+		igc_trigger_rxtxq_interrupt(adapter, rxq_vector);
 
-	q_vector = adapter->q_vector[queue_id];
-	if (!napi_if_scheduled_mark_missed(&q_vector->napi))
-		igc_trigger_rxtxq_interrupt(adapter, q_vector);
+	/* only trigger tx interrupt if the receive interrupt was not
+	 * triggered or if its irq differs from the receive queue's irq
+	 */
+	if (txq_vector != NULL &&
+            txq_vector != rxq_vector &&
+	    !napi_if_scheduled_mark_missed(&txq_vector->napi))
+		igc_trigger_rxtxq_interrupt(adapter, txq_vector);
 
 	return 0;
 }
-- 
2.17.1

Re: [PATCH v2 2/2] igc: Trigger proper interrupts in igc_xsk_wakeup

[Tony Nguyen]

On 4/19/2022 6:26 PM, jeff.evanson@gmail.com wrote:
> From: Jeff Evanson <jeff.evanson@qsc.com>
>
> In igc_xsk_wakeup, trigger the proper interrupt based on whether flags
> contains XDP_WAKEUP_RX and/or XDP_WAKEUP_TX.
>
> Consider a scenario where the transmit queue interrupt is mapped to a
> different irq from the receive queue. If XDP_WAKEUP_TX is set in the
> flags argument, the interrupt for transmit queue must be triggered,
> otherwise the transmit queue's napi_struct will never be scheduled.
>
> In the case where both XDP_WAKEUP_TX and XDP_WAKEUP_RX are both set,
> the receive interrupt should always be triggered, but the transmit
> interrupt should only be triggered if its q_vector differs from the
> receive queue's interrupt.
>
> Fixes: fc9df2a0b520 ("igc: Enable RX via AF_XDP zero-copy")

You're missing your sign-off; same for patch 1. Also, there's a handful 
of issues being reported by checkpatch [1]

Thanks,

Tony

[1] 
https://patchwork.kernel.org/project/netdevbpf/patch/20220420012635.13733-3-jeff.evanson@qsc.com/