From: Maxim Mikityanskiy <maxi...@mellanox.com>
[ Upstream commit d460c2718906252a2a69bc6f89b537071f792e6e ]
MLX5E_XDP_MAX_MTU was calculated incorrectly. It didn't account for
NET_IP_ALIGN and MLX5E_HW2SW_MTU, and it also misused MLX5_SKB_FRAG_SZ.
This commit fixes the calculations and adds a brief explanation for the
formula used.
Fixes: a26a5bdf3ee2d ("net/mlx5e: Restrict the combination of large MTU and
XDP")
Signed-off-by: Maxim Mikityanskiy <maxi...@mellanox.com>
Signed-off-by: Saeed Mahameed <sae...@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c | 20 ++++++++++++++++++++
drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h | 3 +--
drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 5 +++--
3 files changed, 24 insertions(+), 4 deletions(-)
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
@@ -33,6 +33,26 @@
#include <linux/bpf_trace.h>
#include "en/xdp.h"
+int mlx5e_xdp_max_mtu(struct mlx5e_params *params)
+{
+ int hr = NET_IP_ALIGN + XDP_PACKET_HEADROOM;
+
+ /* Let S := SKB_DATA_ALIGN(sizeof(struct skb_shared_info)).
+ * The condition checked in mlx5e_rx_is_linear_skb is:
+ * SKB_DATA_ALIGN(sw_mtu + hard_mtu + hr) + S <= PAGE_SIZE (1)
+ * (Note that hw_mtu == sw_mtu + hard_mtu.)
+ * What is returned from this function is:
+ * max_mtu = PAGE_SIZE - S - hr - hard_mtu (2)
+ * After assigning sw_mtu := max_mtu, the left side of (1) turns to
+ * SKB_DATA_ALIGN(PAGE_SIZE - S) + S, which is equal to PAGE_SIZE,
+ * because both PAGE_SIZE and S are already aligned. Any number greater
+ * than max_mtu would make the left side of (1) greater than PAGE_SIZE,
+ * so max_mtu is the maximum MTU allowed.
+ */
+
+ return MLX5E_HW2SW_MTU(params, SKB_MAX_HEAD(hr));
+}
+
static inline bool
mlx5e_xmit_xdp_buff(struct mlx5e_xdpsq *sq, struct mlx5e_dma_info *di,
struct xdp_buff *xdp)
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h
@@ -34,13 +34,12 @@
#include "en.h"
-#define MLX5E_XDP_MAX_MTU ((int)(PAGE_SIZE - \
- MLX5_SKB_FRAG_SZ(XDP_PACKET_HEADROOM)))
#define MLX5E_XDP_MIN_INLINE (ETH_HLEN + VLAN_HLEN)
#define MLX5E_XDP_TX_EMPTY_DS_COUNT \
(sizeof(struct mlx5e_tx_wqe) / MLX5_SEND_WQE_DS)
#define MLX5E_XDP_TX_DS_COUNT (MLX5E_XDP_TX_EMPTY_DS_COUNT + 1 /* SG DS */)
+int mlx5e_xdp_max_mtu(struct mlx5e_params *params);
bool mlx5e_xdp_handle(struct mlx5e_rq *rq, struct mlx5e_dma_info *di,
void *va, u16 *rx_headroom, u32 *len);
bool mlx5e_poll_xdpsq_cq(struct mlx5e_cq *cq, struct mlx5e_rq *rq);
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -3816,7 +3816,7 @@ int mlx5e_change_mtu(struct net_device *
if (params->xdp_prog &&
!mlx5e_rx_is_linear_skb(priv->mdev, &new_channels.params)) {
netdev_err(netdev, "MTU(%d) > %d is not allowed while XDP
enabled\n",
- new_mtu, MLX5E_XDP_MAX_MTU);
+ new_mtu, mlx5e_xdp_max_mtu(params));
err = -EINVAL;
goto out;
}
@@ -4280,7 +4280,8 @@ static int mlx5e_xdp_allowed(struct mlx5
if (!mlx5e_rx_is_linear_skb(priv->mdev, &new_channels.params)) {
netdev_warn(netdev, "XDP is not allowed with MTU(%d) > %d\n",
- new_channels.params.sw_mtu, MLX5E_XDP_MAX_MTU);
+ new_channels.params.sw_mtu,
+ mlx5e_xdp_max_mtu(&new_channels.params));
return -EINVAL;
}
