netdev - [net 6/6] net/mlx5e: Disable rxhash when CQE compress is enabled

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Date:   Wed, 29 May 2019 02:08:07 +0000
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "David S. Miller" <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Jes Sorensen <jsorensen@...com>
Subject: [net 6/6] net/mlx5e: Disable rxhash when CQE compress is enabled

When CQE compression is enabled (Multi-host systems), compressed CQEs
might arrive to the driver rx, compressed CQEs don't have a valid hash
offload and the driver already reports a hash value of 0 and invalid hash
type on the skb for compressed CQEs, but this is not good enough.

On a congested PCIe, where CQE compression will kick in aggressively,
gro will deliver lots of out of order packets due to the invalid hash
and this might cause a serious performance drop.

The only valid solution, is to disable rxhash offload at all when CQE
compression is favorable (Multi-host systems).

Fixes: 7219ab34f184 ("net/mlx5e: CQE compression")
CC: Jes Sorensen <jsorensen@...com>
Signed-off-by: Saeed Mahameed <saeedm@...lanox.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 457cc39423f2..c65cefd84eda 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -3687,6 +3687,12 @@ static netdev_features_t mlx5e_fix_features(struct net_device *netdev,
 			netdev_warn(netdev, "Disabling LRO, not supported in legacy RQ\n");
 	}
 
+	if (MLX5E_GET_PFLAG(params, MLX5E_PFLAG_RX_CQE_COMPRESS)) {
+		features &= ~NETIF_F_RXHASH;
+		if (netdev->features & NETIF_F_RXHASH)
+			netdev_warn(netdev, "Disabling rxhash, not supported when CQE compress is active\n");
+	}
+
 	mutex_unlock(&priv->state_lock);
 
 	return features;
@@ -3812,6 +3818,9 @@ int mlx5e_hwstamp_set(struct mlx5e_priv *priv, struct ifreq *ifr)
 	memcpy(&priv->tstamp, &config, sizeof(config));
 	mutex_unlock(&priv->state_lock);
 
+	/* might need to fix some features */
+	netdev_update_features(priv->netdev);
+
 	return copy_to_user(ifr->ifr_data, &config,
 			    sizeof(config)) ? -EFAULT : 0;
 }
@@ -4680,6 +4689,10 @@ static void mlx5e_build_nic_netdev(struct net_device *netdev)
 	if (!priv->channels.params.scatter_fcs_en)
 		netdev->features  &= ~NETIF_F_RXFCS;
 
+	/* prefere CQE compression over rxhash */
+	if (MLX5E_GET_PFLAG(&priv->channels.params, MLX5E_PFLAG_RX_CQE_COMPRESS))
+		netdev->features &= ~NETIF_F_RXHASH;
+
 #define FT_CAP(f) MLX5_CAP_FLOWTABLE(mdev, flow_table_properties_nic_receive.f)
 	if (FT_CAP(flow_modify_en) &&
 	    FT_CAP(modify_root) &&
-- 
2.21.0