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Subject[PATCH 5.4 120/165] net/mlx5e: Fix concurrency issues between config flow and XSK
Date
From: Maxim Mikityanskiy <maximmi@mellanox.com>

[ Upstream commit 9cf88808ad6a0f1e958e00abd9a081295fe6da0c ]

After disabling resources necessary for XSK (the XDP program, channels,
XSK queues), use synchronize_rcu to wait until the XSK wakeup function
finishes, before freeing the resources.

Suspend XSK wakeups during switching channels. If the XDP program is
being removed, synchronize_rcu before closing the old channels to allow
XSK wakeup to complete.

Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191217162023.16011-3-maximmi@mellanox.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/mellanox/mlx5/core/en.h | 2 +-
.../net/ethernet/mellanox/mlx5/core/en/xdp.h | 22 ++++++++-----------
.../mellanox/mlx5/core/en/xsk/setup.c | 1 +
.../ethernet/mellanox/mlx5/core/en/xsk/tx.c | 2 +-
.../net/ethernet/mellanox/mlx5/core/en_main.c | 19 +---------------
5 files changed, 13 insertions(+), 33 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
index 2c16add0b642..9c8427698238 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -760,7 +760,7 @@ enum {
MLX5E_STATE_OPENED,
MLX5E_STATE_DESTROYING,
MLX5E_STATE_XDP_TX_ENABLED,
- MLX5E_STATE_XDP_OPEN,
+ MLX5E_STATE_XDP_ACTIVE,
};

struct mlx5e_rqt {
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h
index 36ac1e3816b9..d7587f40ecae 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h
@@ -75,12 +75,18 @@ int mlx5e_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames,
static inline void mlx5e_xdp_tx_enable(struct mlx5e_priv *priv)
{
set_bit(MLX5E_STATE_XDP_TX_ENABLED, &priv->state);
+
+ if (priv->channels.params.xdp_prog)
+ set_bit(MLX5E_STATE_XDP_ACTIVE, &priv->state);
}

static inline void mlx5e_xdp_tx_disable(struct mlx5e_priv *priv)
{
+ if (priv->channels.params.xdp_prog)
+ clear_bit(MLX5E_STATE_XDP_ACTIVE, &priv->state);
+
clear_bit(MLX5E_STATE_XDP_TX_ENABLED, &priv->state);
- /* let other device's napi(s) see our new state */
+ /* Let other device's napi(s) and XSK wakeups see our new state. */
synchronize_rcu();
}

@@ -89,19 +95,9 @@ static inline bool mlx5e_xdp_tx_is_enabled(struct mlx5e_priv *priv)
return test_bit(MLX5E_STATE_XDP_TX_ENABLED, &priv->state);
}

-static inline void mlx5e_xdp_set_open(struct mlx5e_priv *priv)
-{
- set_bit(MLX5E_STATE_XDP_OPEN, &priv->state);
-}
-
-static inline void mlx5e_xdp_set_closed(struct mlx5e_priv *priv)
-{
- clear_bit(MLX5E_STATE_XDP_OPEN, &priv->state);
-}
-
-static inline bool mlx5e_xdp_is_open(struct mlx5e_priv *priv)
+static inline bool mlx5e_xdp_is_active(struct mlx5e_priv *priv)
{
- return test_bit(MLX5E_STATE_XDP_OPEN, &priv->state);
+ return test_bit(MLX5E_STATE_XDP_ACTIVE, &priv->state);
}

static inline void mlx5e_xmit_xdp_doorbell(struct mlx5e_xdpsq *sq)
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c
index 631af8dee517..c28cbae42331 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c
@@ -144,6 +144,7 @@ void mlx5e_close_xsk(struct mlx5e_channel *c)
{
clear_bit(MLX5E_CHANNEL_STATE_XSK, c->state);
napi_synchronize(&c->napi);
+ synchronize_rcu(); /* Sync with the XSK wakeup. */

mlx5e_close_rq(&c->xskrq);
mlx5e_close_cq(&c->xskrq.cq);
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c
index 87827477d38c..fe2d596cb361 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c
@@ -14,7 +14,7 @@ int mlx5e_xsk_wakeup(struct net_device *dev, u32 qid, u32 flags)
struct mlx5e_channel *c;
u16 ix;

- if (unlikely(!mlx5e_xdp_is_open(priv)))
+ if (unlikely(!mlx5e_xdp_is_active(priv)))
return -ENETDOWN;

if (unlikely(!mlx5e_qid_get_ch_if_in_group(params, qid, MLX5E_RQ_GROUP_XSK, &ix)))
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 6abd4ed5b69b..29a5a8c894e3 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -3002,12 +3002,9 @@ void mlx5e_timestamp_init(struct mlx5e_priv *priv)
int mlx5e_open_locked(struct net_device *netdev)
{
struct mlx5e_priv *priv = netdev_priv(netdev);
- bool is_xdp = priv->channels.params.xdp_prog;
int err;

set_bit(MLX5E_STATE_OPENED, &priv->state);
- if (is_xdp)
- mlx5e_xdp_set_open(priv);

err = mlx5e_open_channels(priv, &priv->channels);
if (err)
@@ -3022,8 +3019,6 @@ int mlx5e_open_locked(struct net_device *netdev)
return 0;

err_clear_state_opened_flag:
- if (is_xdp)
- mlx5e_xdp_set_closed(priv);
clear_bit(MLX5E_STATE_OPENED, &priv->state);
return err;
}
@@ -3055,8 +3050,6 @@ int mlx5e_close_locked(struct net_device *netdev)
if (!test_bit(MLX5E_STATE_OPENED, &priv->state))
return 0;

- if (priv->channels.params.xdp_prog)
- mlx5e_xdp_set_closed(priv);
clear_bit(MLX5E_STATE_OPENED, &priv->state);

netif_carrier_off(priv->netdev);
@@ -4373,16 +4366,6 @@ static int mlx5e_xdp_allowed(struct mlx5e_priv *priv, struct bpf_prog *prog)
return 0;
}

-static int mlx5e_xdp_update_state(struct mlx5e_priv *priv)
-{
- if (priv->channels.params.xdp_prog)
- mlx5e_xdp_set_open(priv);
- else
- mlx5e_xdp_set_closed(priv);
-
- return 0;
-}
-
static int mlx5e_xdp_set(struct net_device *netdev, struct bpf_prog *prog)
{
struct mlx5e_priv *priv = netdev_priv(netdev);
@@ -4422,7 +4405,7 @@ static int mlx5e_xdp_set(struct net_device *netdev, struct bpf_prog *prog)
mlx5e_set_rq_type(priv->mdev, &new_channels.params);
old_prog = priv->channels.params.xdp_prog;

- err = mlx5e_safe_switch_channels(priv, &new_channels, mlx5e_xdp_update_state);
+ err = mlx5e_safe_switch_channels(priv, &new_channels, NULL);
if (err)
goto unlock;
} else {
--
2.20.1


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