ice: unify xdp_rings accesses

There has been a long lasting issue of improper xdp_rings indexing for
XDP_TX and XDP_REDIRECT actions. Given that currently rx_ring->q_index
is mixed with smp_processor_id(), there could be a situation where Tx
descriptors are produced onto XDP Tx ring, but tail is never bumped -
for example pin a particular queue id to non-matching IRQ line.

Address this problem by ignoring the user ring count setting and always
initialize the xdp_rings array to be of num_possible_cpus() size. Then,
always use the smp_processor_id() as an index to xdp_rings array. This
provides serialization as at given time only a single softirq can run on
a particular CPU.

Signed-off-by: Maciej Fijalkowski <[email protected]>
Tested-by: George Kuruvinakunnel <[email protected]>
Signed-off-by: Tony Nguyen <[email protected]>

Author: mfijalko

drivers/net/ethernet/intel/ice/ice_lib.c

@@ -3215,7 +3215,7 @@ int ice_vsi_rebuild(struct ice_vsi *vsi, bool init_vsi)
 
 		ice_vsi_map_rings_to_vectors(vsi);
 		if (ice_is_xdp_ena_vsi(vsi)) {
-			vsi->num_xdp_txq = vsi->alloc_rxq;
+			vsi->num_xdp_txq = num_possible_cpus();
 			ret = ice_prepare_xdp_rings(vsi, vsi->xdp_prog);
 			if (ret)
 				goto err_vectors;

drivers/net/ethernet/intel/ice/ice_main.c

@@ -2638,7 +2638,7 @@ ice_xdp_setup_prog(struct ice_vsi *vsi, struct bpf_prog *prog,
 	}
 
 	if (!ice_is_xdp_ena_vsi(vsi) && prog) {
-		vsi->num_xdp_txq = vsi->alloc_rxq;
+		vsi->num_xdp_txq = num_possible_cpus();
 		xdp_ring_err = ice_prepare_xdp_rings(vsi, prog);
 		if (xdp_ring_err)
 			NL_SET_ERR_MSG_MOD(extack, "Setting up XDP Tx resources failed");

drivers/net/ethernet/intel/ice/ice_txrx_lib.c

@@ -297,7 +297,7 @@ void ice_finalize_xdp_rx(struct ice_rx_ring *rx_ring, unsigned int xdp_res)
 
 	if (xdp_res & ICE_XDP_TX) {
 		struct ice_tx_ring *xdp_ring =
-			rx_ring->vsi->xdp_rings[rx_ring->q_index];
+			rx_ring->vsi->xdp_rings[smp_processor_id()];
 
 		ice_xdp_ring_update_tail(xdp_ring);
 	}