i40e: clean zero-copy XDP Tx ring on shutdown/reset

When the zero-copy enabled XDP Tx ring is torn down, due to
configuration changes, outstanding frames on the hardware descriptor
ring are queued on the completion ring.

The completion ring has a back-pressure mechanism that will guarantee
that there is sufficient space on the ring.
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -636,13 +636,18 @@ void i40e_clean_tx_ring(struct i40e_ring *tx_ring)
 	unsigned long bi_size;
 	u16 i;
 
+	if (ring_is_xdp(tx_ring) && tx_ring->xsk_umem) {
+		i40e_xsk_clean_tx_ring(tx_ring);
+	} else {
 		/* ring already cleared, nothing to do */
 		if (!tx_ring->tx_bi)
 			return;
 
 		/* Free all the Tx ring sk_buffs */
 		for (i = 0; i < tx_ring->count; i++)
-		i40e_unmap_and_free_tx_resource(tx_ring, &tx_ring->tx_bi[i]);
+			i40e_unmap_and_free_tx_resource(tx_ring,
+							&tx_ring->tx_bi[i]);
+	}
 
 	bi_size = sizeof(struct i40e_tx_buffer) * tx_ring->count;
 	memset(tx_ring->tx_bi, 0, bi_size);

drivers/net/ethernet/intel/i40e/i40e_txrx_common.h

@@ -87,4 +87,6 @@ static inline void i40e_arm_wb(struct i40e_ring *tx_ring,
 	}
 }
 
+void i40e_xsk_clean_tx_ring(struct i40e_ring *tx_ring);
+
 #endif /* I40E_TXRX_COMMON_ */

drivers/net/ethernet/intel/i40e/i40e_xsk.c

@@ -830,3 +830,33 @@ int i40e_xsk_async_xmit(struct net_device *dev, u32 queue_id)
 
 	return 0;
 }
+
+/**
+ * i40e_xsk_clean_xdp_ring - Clean the XDP Tx ring on shutdown
+ * @xdp_ring: XDP Tx ring
+ **/
+void i40e_xsk_clean_tx_ring(struct i40e_ring *tx_ring)
+{
+	u16 ntc = tx_ring->next_to_clean, ntu = tx_ring->next_to_use;
+	struct xdp_umem *umem = tx_ring->xsk_umem;
+	struct i40e_tx_buffer *tx_bi;
+	u32 xsk_frames = 0;
+
+	while (ntc != ntu) {
+		tx_bi = &tx_ring->tx_bi[ntc];
+
+		if (tx_bi->xdpf)
+			i40e_clean_xdp_tx_buffer(tx_ring, tx_bi);
+		else
+			xsk_frames++;
+
+		tx_bi->xdpf = NULL;
+
+		ntc++;
+		if (ntc >= tx_ring->count)
+			ntc = 0;
+	}
+
+	if (xsk_frames)
+		xsk_umem_complete_tx(umem, xsk_frames);
+}