Save per-channel resources in default.

As no better API exist, make the XDP-redirect-target SQ available by
loading a dummy XDP program.

This improves the latency of interface up/down operations when feature
is disabled.

Perf numbers:
NIC: Connect-X7.
Setup: 248 channels.

Interface up + down:
Before: 2.246 secs
After:  1.798 secs (1.25x faster)

Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: William Tu <witu@nvidia.com>
---
 .../net/ethernet/mellanox/mlx5/core/en_main.c | 23 +++++++++----------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 078fd591c540..23a0b50b9dbd 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -2652,7 +2652,7 @@ static int mlx5e_open_queues(struct mlx5e_channel *c,
 	if (err)
 		goto err_close_icosq_cq;
 
-	if (netdev_ops->ndo_xdp_xmit) {
+	if (netdev_ops->ndo_xdp_xmit && c->xdp) {
 		c->xdpsq = mlx5e_open_xdpredirect_sq(c, params, cparam, &ccp);
 		if (IS_ERR(c->xdpsq)) {
 			err = PTR_ERR(c->xdpsq);
@@ -4467,19 +4467,18 @@ void mlx5e_set_xdp_feature(struct mlx5e_priv *priv)
 {
 	struct mlx5e_params *params = &priv->channels.params;
 	struct net_device *netdev = priv->netdev;
-	xdp_features_t val;
+	xdp_features_t val = 0;
 
-	if (!netdev->netdev_ops->ndo_bpf ||
-	    params->packet_merge.type != MLX5E_PACKET_MERGE_NONE) {
-		xdp_set_features_flag_locked(netdev, 0);
-		return;
-	}
+	if (netdev->netdev_ops->ndo_bpf &&
+	    params->packet_merge.type == MLX5E_PACKET_MERGE_NONE)
+		val = NETDEV_XDP_ACT_BASIC | NETDEV_XDP_ACT_REDIRECT |
+		      NETDEV_XDP_ACT_XSK_ZEROCOPY |
+		      NETDEV_XDP_ACT_RX_SG;
+
+	if (netdev->netdev_ops->ndo_xdp_xmit && params->xdp_prog)
+		val |= NETDEV_XDP_ACT_NDO_XMIT |
+			NETDEV_XDP_ACT_NDO_XMIT_SG;
 
-	val = NETDEV_XDP_ACT_BASIC | NETDEV_XDP_ACT_REDIRECT |
-	      NETDEV_XDP_ACT_XSK_ZEROCOPY |
-	      NETDEV_XDP_ACT_RX_SG |
-	      NETDEV_XDP_ACT_NDO_XMIT |
-	      NETDEV_XDP_ACT_NDO_XMIT_SG;
 	xdp_set_features_flag_locked(netdev, val);
 }
 
-- 
2.31.1

Tariq Toukan <tariqt@nvidia.com> writes:

> Save per-channel resources in default.
>
> As no better API exist, make the XDP-redirect-target SQ available by
> loading a dummy XDP program.

This is a user-visible change, though, no? I.e., after this patch
xdp_redirect mlx5 devices will no longer work as an xdp_redirect target
out of the box?

We have userspace code listing the driver support in various places
(e.g., here in xdp-tools:
https://github.com/xdp-project/xdp-tools/commit/1dad1d6e0ccb086b8a31496931f21a165b42b700);
I'm sure there will be other places. Since such code would up until now
assume that mlx5 just works, this will end up being a regression in such
cases, no?

-Toke

On 12/11/2025 12:29, Toke Høiland-Jørgensen wrote:
> Tariq Toukan <tariqt@nvidia.com> writes:
> 
>> Save per-channel resources in default.
>>
>> As no better API exist, make the XDP-redirect-target SQ available by
>> loading a dummy XDP program.
> 
> This is a user-visible change, though, no? I.e., after this patch
> xdp_redirect mlx5 devices will no longer work as an xdp_redirect target
> out of the box?
> 

Right, we introduce an explicit behavior change here.
Due to the lack of a standard control, we're aligning to other drivers 
and use the dummy program trick.
Having the feature always on by default wastes HW and SW resources for 
users who are not interested in the feature (and cannot explicitly 
disable it), in addition to the significant extra latency it adds in 
configuration flow.

> We have userspace code listing the driver support in various places
> (e.g., here in xdp-tools:
> https://github.com/xdp-project/xdp-tools/commit/1dad1d6e0ccb086b8a31496931f21a165b42b700);
> I'm sure there will be other places. Since such code would up until now
> assume that mlx5 just works, this will end up being a regression in such
> cases, no?
> 
> -Toke
> 
> 

Yes, it is indeed a change in behavior.
Now the feature can be turned off, and actually defaults to off.
Now we should add "mlx5" to this list driver_pass_list[].