[PATCH net-next 1/5] net/mlx5e: remove channel count limit for XOR8 RSS hash

[Tariq Toukan]

From: Yael Chemla <ychemla@xxxxxxxxxx>

mlx5e_ethtool_set_channels() and mlx5e_rxfh_hfunc_check() rejected
channel counts that would produce an indirection table larger than 256
entries when the XOR8 hash function was active. This check was
introduced in commit 49e6c9387051 ("net/mlx5e: RSS, Block XOR hash
with over 128 channels").

XOR8 yields an 8-bit hash, so in practice only up to 256 entries in the
indirection table can be reached due to limited entropy. However, this
does not provide a strong justification for prohibiting larger
indirection tables. Remove the limitation.

Signed-off-by: Yael Chemla <ychemla@xxxxxxxxxx>
Reviewed-by: Nimrod Oren <noren@xxxxxxxxxx>
Signed-off-by: Tariq Toukan <tariqt@xxxxxxxxxx>
---
 .../net/ethernet/mellanox/mlx5/core/en/rqt.c  |  7 ---
 .../net/ethernet/mellanox/mlx5/core/en/rqt.h  |  1 -
 .../ethernet/mellanox/mlx5/core/en_ethtool.c  | 48 -------------------
 3 files changed, 56 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/rqt.c b/drivers/net/ethernet/mellanox/mlx5/core/en/rqt.c
index 8d9a3b5ec973..bcafb4bf9415 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/rqt.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/rqt.c
@@ -179,13 +179,6 @@ u32 mlx5e_rqt_size(struct mlx5_core_dev *mdev, unsigned int num_channels)
 	return min_t(u32, rqt_size, max_cap_rqt_size);
 }
 
-#define MLX5E_MAX_RQT_SIZE_ALLOWED_WITH_XOR8_HASH 256
-
-unsigned int mlx5e_rqt_max_num_channels_allowed_for_xor8(void)
-{
-	return MLX5E_MAX_RQT_SIZE_ALLOWED_WITH_XOR8_HASH / MLX5E_UNIFORM_SPREAD_RQT_FACTOR;
-}
-
 void mlx5e_rqt_destroy(struct mlx5e_rqt *rqt)
 {
 	mlx5_core_destroy_rqt(rqt->mdev, rqt->rqtn);
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/rqt.h b/drivers/net/ethernet/mellanox/mlx5/core/en/rqt.h
index 2f9e04a8418f..e0bc30308c77 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/rqt.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/rqt.h
@@ -38,7 +38,6 @@ static inline u32 mlx5e_rqt_get_rqtn(struct mlx5e_rqt *rqt)
 }
 
 u32 mlx5e_rqt_size(struct mlx5_core_dev *mdev, unsigned int num_channels);
-unsigned int mlx5e_rqt_max_num_channels_allowed_for_xor8(void);
 int mlx5e_rqt_redirect_direct(struct mlx5e_rqt *rqt, u32 rqn, u32 *vhca_id);
 int mlx5e_rqt_redirect_indir(struct mlx5e_rqt *rqt, u32 *rqns, u32 *vhca_ids,
 			     unsigned int num_rqns,
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c b/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c
index bb61e2179078..a6da0219723c 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c
@@ -511,17 +511,6 @@ int mlx5e_ethtool_set_channels(struct mlx5e_priv *priv,
 
 	mutex_lock(&priv->state_lock);
 
-	if (mlx5e_rx_res_get_current_hash(priv->rx_res).hfunc == ETH_RSS_HASH_XOR) {
-		unsigned int xor8_max_channels = mlx5e_rqt_max_num_channels_allowed_for_xor8();
-
-		if (count > xor8_max_channels) {
-			err = -EINVAL;
-			netdev_err(priv->netdev, "%s: Requested number of channels (%d) exceeds the maximum allowed by the XOR8 RSS hfunc (%d)\n",
-				   __func__, count, xor8_max_channels);
-			goto out;
-		}
-	}
-
 	/* If RXFH is configured, changing the channels number is allowed only if
 	 * it does not require resizing the RSS table. This is because the previous
 	 * configuration may no longer be compatible with the new RSS table.
@@ -1501,29 +1490,6 @@ static int mlx5e_get_rxfh(struct net_device *netdev, struct ethtool_rxfh_param *
 	return 0;
 }
 
-static int mlx5e_rxfh_hfunc_check(struct mlx5e_priv *priv,
-				  const struct ethtool_rxfh_param *rxfh,
-				  struct netlink_ext_ack *extack)
-{
-	unsigned int count;
-
-	count = priv->channels.params.num_channels;
-
-	if (rxfh->hfunc == ETH_RSS_HASH_XOR) {
-		unsigned int xor8_max_channels = mlx5e_rqt_max_num_channels_allowed_for_xor8();
-
-		if (count > xor8_max_channels) {
-			NL_SET_ERR_MSG_FMT_MOD(
-				extack,
-				"Number of channels (%u) exceeds the max for XOR8 RSS (%u)",
-				count, xor8_max_channels);
-			return -EINVAL;
-		}
-	}
-
-	return 0;
-}
-
 static int mlx5e_set_rxfh(struct net_device *dev,
 			  struct ethtool_rxfh_param *rxfh,
 			  struct netlink_ext_ack *extack)
@@ -1535,16 +1501,11 @@ static int mlx5e_set_rxfh(struct net_device *dev,
 
 	mutex_lock(&priv->state_lock);
 
-	err = mlx5e_rxfh_hfunc_check(priv, rxfh, extack);
-	if (err)
-		goto unlock;
-
 	err = mlx5e_rx_res_rss_set_rxfh(priv->rx_res, rxfh->rss_context,
 					rxfh->indir, rxfh->key,
 					hfunc == ETH_RSS_HASH_NO_CHANGE ? NULL : &hfunc,
 					rxfh->input_xfrm == RXH_XFRM_NO_CHANGE ? NULL : &symmetric);
 
-unlock:
 	mutex_unlock(&priv->state_lock);
 	return err;
 }
@@ -1561,10 +1522,6 @@ static int mlx5e_create_rxfh_context(struct net_device *dev,
 
 	mutex_lock(&priv->state_lock);
 
-	err = mlx5e_rxfh_hfunc_check(priv, rxfh, extack);
-	if (err)
-		goto unlock;
-
 	err = mlx5e_rx_res_rss_init(priv->rx_res, rxfh->rss_context,
 				    priv->channels.params.num_channels);
 	if (err)
@@ -1601,16 +1558,11 @@ static int mlx5e_modify_rxfh_context(struct net_device *dev,
 
 	mutex_lock(&priv->state_lock);
 
-	err = mlx5e_rxfh_hfunc_check(priv, rxfh, extack);
-	if (err)
-		goto unlock;
-
 	err = mlx5e_rx_res_rss_set_rxfh(priv->rx_res, rxfh->rss_context,
 					rxfh->indir, rxfh->key,
 					hfunc == ETH_RSS_HASH_NO_CHANGE ? NULL : &hfunc,
 					rxfh->input_xfrm == RXH_XFRM_NO_CHANGE ? NULL : &symmetric);
 
-unlock:
 	mutex_unlock(&priv->state_lock);
 	return err;
 }
-- 
2.44.0