i40e: setup xdp_rxq_info

The i40e driver has a special "FDIR" RX-ring (I40E_VSI_FDIR) which is
a sideband channel for configuring/updating the flow director tables.
This (i40e_vsi_)type does not invoke XDP-ebpf code.

As suggested by Björn (V2): Instead of marking this I40E_VSI_FDIR RX-ring
a special case, reverse the logic and only select RX-rings of type
I40E_VSI_MAIN to register xdp_rxq_info's for.

Driver hook points for xdp_rxq_info:
 * reg  : i40e_setup_rx_descriptors (via i40e_vsi_setup_rx_resources)
 * unreg: i40e_free_rx_resources    (via i40e_vsi_free_rx_resources)

Tested on actual hardware with samples/bpf program.

V2: Fixed bug in i40e_set_ringparam (memset zero) + match on I40E_VSI_MAIN.
V4: Update patch desc that got out-of-sync with code.

Cc: intel-wired-lan@lists.osuosl.org
Cc: Björn Töpel <bjorn.topel@intel.com>
Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

drivers/net/ethernet/intel/i40e/i40e_ethtool.c

@@ -1585,6 +1585,8 @@ static int i40e_set_ringparam(struct net_device *netdev,
 			 */
 			rx_rings[i].desc = NULL;
 			rx_rings[i].rx_bi = NULL;
+			/* Clear cloned XDP RX-queue info before setup call */
+			memset(&rx_rings[i].xdp_rxq, 0, sizeof(rx_rings[i].xdp_rxq));
 			/* this is to allow wr32 to have something to write to
 			 * during early allocation of Rx buffers
 			 */

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

@@ -27,6 +27,7 @@
 #include <linux/prefetch.h>
 #include <net/busy_poll.h>
 #include <linux/bpf_trace.h>
+#include <net/xdp.h>
 #include "i40e.h"
 #include "i40e_trace.h"
 #include "i40e_prototype.h"
@@ -1236,6 +1237,8 @@ void i40e_clean_rx_ring(struct i40e_ring *rx_ring)
 void i40e_free_rx_resources(struct i40e_ring *rx_ring)
 {
 	i40e_clean_rx_ring(rx_ring);
+	if (rx_ring->vsi->type == I40E_VSI_MAIN)
+		xdp_rxq_info_unreg(&rx_ring->xdp_rxq);
 	rx_ring->xdp_prog = NULL;
 	kfree(rx_ring->rx_bi);
 	rx_ring->rx_bi = NULL;
@@ -1256,6 +1259,7 @@ void i40e_free_rx_resources(struct i40e_ring *rx_ring)
 int i40e_setup_rx_descriptors(struct i40e_ring *rx_ring)
 {
 	struct device *dev = rx_ring->dev;
+	int err = -ENOMEM;
 	int bi_size;
 
 	/* warn if we are about to overwrite the pointer */
@@ -1283,13 +1287,21 @@ int i40e_setup_rx_descriptors(struct i40e_ring *rx_ring)
 	rx_ring->next_to_clean = 0;
 	rx_ring->next_to_use = 0;
 
+	/* XDP RX-queue info only needed for RX rings exposed to XDP */
+	if (rx_ring->vsi->type == I40E_VSI_MAIN) {
+		err = xdp_rxq_info_reg(&rx_ring->xdp_rxq, rx_ring->netdev,
+				       rx_ring->queue_index);
+		if (err < 0)
+			goto err;
+	}
+
 	rx_ring->xdp_prog = rx_ring->vsi->xdp_prog;
 
 	return 0;
 err:
 	kfree(rx_ring->rx_bi);
 	rx_ring->rx_bi = NULL;
-	return -ENOMEM;
+	return err;
 }
 
 /**
@@ -2068,11 +2080,13 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget)
 	struct sk_buff *skb = rx_ring->skb;
 	u16 cleaned_count = I40E_DESC_UNUSED(rx_ring);
 	bool failure = false, xdp_xmit = false;
+	struct xdp_buff xdp;
+
+	xdp.rxq = &rx_ring->xdp_rxq;
 
 	while (likely(total_rx_packets < (unsigned int)budget)) {
 		struct i40e_rx_buffer *rx_buffer;
 		union i40e_rx_desc *rx_desc;
-		struct xdp_buff xdp;
 		unsigned int size;
 		u16 vlan_tag;
 		u8 rx_ptype;

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

@@ -27,6 +27,8 @@
 #ifndef _I40E_TXRX_H_
 #define _I40E_TXRX_H_
 
+#include <net/xdp.h>
+
 /* Interrupt Throttling and Rate Limiting Goodies */
 
 #define I40E_MAX_ITR               0x0FF0  /* reg uses 2 usec resolution */
@@ -428,6 +430,7 @@ struct i40e_ring {
 					 */
 
 	struct i40e_channel *ch;
+	struct xdp_rxq_info xdp_rxq;
 } ____cacheline_internodealigned_in_smp;
 
 static inline bool ring_uses_build_skb(struct i40e_ring *ring)