netdev - [PATCH iwl-next] ice: allow hot-swapping XDP programs

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Date: Tue, 13 Jun 2023 17:10:05 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: intel-wired-lan@...ts.osuosl.org
Cc: netdev@...r.kernel.org,
	anthony.l.nguyen@...el.com,
	magnus.karlsson@...el.com,
	fred@...udflare.com,
	Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Subject: [PATCH iwl-next] ice: allow hot-swapping XDP programs

Currently ice driver's .ndo_bpf callback brings the interface down and
up independently of the presence of XDP resources. This is only needed
when either these resources have to be configured or removed. It means
that if one is switching XDP programs on-the-fly with running traffic,
packets will be dropped.

To avoid this, compare early on ice_xdp_setup_prog() state of incoming
bpf_prog pointer vs the bpf_prog pointer that is already assigned to
VSI. Do the swap in case VSI has bpf_prog and incoming one are non-NULL.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
---
 drivers/net/ethernet/intel/ice/ice_main.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
index a1f7c8edc22f..8940ee505811 100644
--- a/drivers/net/ethernet/intel/ice/ice_main.c
+++ b/drivers/net/ethernet/intel/ice/ice_main.c
@@ -2922,6 +2922,11 @@ ice_xdp_setup_prog(struct ice_vsi *vsi, struct bpf_prog *prog,
 					   "MTU is too large for linear frames and XDP prog does not support frags");
 			return -EOPNOTSUPP;
 		}
+
+	/* hot swap progs and avoid toggling link */
+	if (ice_is_xdp_ena_vsi(vsi) == !!prog) {
+		ice_vsi_assign_bpf_prog(vsi, prog);
+		return 0;
 	}
 
 	/* need to stop netdev while setting up the program for Rx rings */
@@ -2956,13 +2961,6 @@ ice_xdp_setup_prog(struct ice_vsi *vsi, struct bpf_prog *prog,
 		xdp_ring_err = ice_realloc_zc_buf(vsi, false);
 		if (xdp_ring_err)
 			NL_SET_ERR_MSG_MOD(extack, "Freeing XDP Rx resources failed");
-	} else {
-		/* safe to call even when prog == vsi->xdp_prog as
-		 * dev_xdp_install in net/core/dev.c incremented prog's
-		 * refcount so corresponding bpf_prog_put won't cause
-		 * underflow
-		 */
-		ice_vsi_assign_bpf_prog(vsi, prog);
 	}
 
 	if (if_running)
-- 
2.34.1