[PATCH 4.19 21/32] net/mlx5e: Disable rxhash when CQE compress is enabled

Greg Kroah-Hartman
2019-06-03T09:10:17Z

From: Saeed Mahameed <saeedm@mellanox.com>

[ Upstream commit c0194e2d0ef0e5ce5e21a35640d23a706827ae28 ]

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")
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -3734,6 +3734,12 @@ static netdev_features_t mlx5e_fix_featu
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;
@@ -3860,6 +3866,9 @@ int mlx5e_hwstamp_set(struct mlx5e_priv
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;
}
@@ -4702,6 +4711,10 @@ static void mlx5e_build_nic_netdev(struc
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) &&