netdev - [PATCH v2 iwl-next] ice: allow hot-swapping XDP programs

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Message-Id: <20230613231523.339413-1-maciej.fijalkowski@intel.com>
Date: Wed, 14 Jun 2023 01:15:23 +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 v2 iwl-next] ice: allow hot-swapping XDP programs

Currently ice driver's .ndo_bpf callback brings interface down and up
independently of XDP resources' presence. 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>
---

v1->v2:
- fix missing brace (sigh)

 drivers/net/ethernet/intel/ice/ice_main.c | 13 ++++++-------
 1 file changed, 6 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..dba1f7709e8b 100644
--- a/drivers/net/ethernet/intel/ice/ice_main.c
+++ b/drivers/net/ethernet/intel/ice/ice_main.c
@@ -2924,6 +2924,12 @@ ice_xdp_setup_prog(struct ice_vsi *vsi, struct bpf_prog *prog,
 		}
 	}
 
+	/* 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 */
 	if (if_running && !test_and_set_bit(ICE_VSI_DOWN, vsi->state)) {
 		ret = ice_down(vsi);
@@ -2956,13 +2962,6 @@ 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