Commit 8bf30be7 authored by Maxim Mikityanskiy's avatar Maxim Mikityanskiy Committed by Saeed Mahameed
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net/mlx5e: Introduce select queue parameters 



ndo_select_queue can be called at any time, and there is no way to stop
the kernel from calling it to synchronize with configuration changes
(real_num_tx_queues, num_tc). This commit introduces an internal way in
mlx5e to sync mlx5e_select_queue() with these changes. The configuration
needed by this function is stored in a struct mlx5e_selq_params, which
is modified and accessed in an atomic way using RCU methods. The whole
ndo_select_queue is called under an RCU lock, providing the necessary
guarantees.

The parameters stored in the new struct mlx5e_selq_params should only be
used from inside mlx5e_select_queue. It's the minimal set of parameters
needed for mlx5e_select_queue to do its job efficiently, derived from
parameters stored elsewhere. That means that when the configuration
change, mlx5e_selq_params may need to be updated. In such cases, the
mlx5e_selq_prepare/mlx5e_selq_apply API should be used.

struct mlx5e_selq contains two slots for the params: active and standby.
mlx5e_selq_prepare updates the standby slot, and mlx5e_selq_apply swaps
the slots in a safe atomic way using the RCU API. It integrates well
with the open/activate stages of the configuration change flow.

Signed-off-by: default avatarMaxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: default avatarTariq Toukan <tariqt@nvidia.com>
Signed-off-by: default avatarSaeed Mahameed <saeedm@nvidia.com>
parent 17c84cb4

drivers/net/ethernet/mellanox/mlx5/core/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -28,7 +28,7 @@ mlx5_core-$(CONFIG_MLX5_CORE_EN) += en/rqt.o en/tir.o en/rss.o en/rx_res.o \ 
		en_selftest.o en/port.o en/monitor_stats.o en/health.o \

		en/reporter_tx.o en/reporter_rx.o en/params.o en/xsk/pool.o \

		en/xsk/setup.o en/xsk/rx.o en/xsk/tx.o en/devlink.o en/ptp.o \

		en/qos.o en/trap.o en/fs_tt_redirect.o

		en/qos.o en/trap.o en/fs_tt_redirect.o en/selq.o



#

# Netdev extra

drivers/net/ethernet/mellanox/mlx5/core/en.h

+2 −0
Original line number Diff line number Diff line
@@ -59,6 +59,7 @@ 
#include "lib/hv_vhca.h"

#include "lib/clock.h"

#include "en/rx_res.h"

#include "en/selq.h"



extern const struct net_device_ops mlx5e_netdev_ops;

struct page_pool;
@@ -908,6 +909,7 @@ struct mlx5e_trap; 


struct mlx5e_priv {

	/* priv data path fields - start */

	struct mlx5e_selq selq;

	struct mlx5e_txqsq **txq2sq;

	int **channel_tc2realtxq;

	int port_ptp_tc2realtxq[MLX5E_MAX_NUM_TC];

drivers/net/ethernet/mellanox/mlx5/core/en/qos.c

+11 −1
Original line number Diff line number Diff line
@@ -501,9 +501,11 @@ int mlx5e_htb_root_add(struct mlx5e_priv *priv, u16 htb_maj_id, u16 htb_defcls, 


	opened = test_bit(MLX5E_STATE_OPENED, &priv->state);

	if (opened) {

		mlx5e_selq_prepare(&priv->selq, &priv->channels.params, true);



		err = mlx5e_qos_alloc_queues(priv, &priv->channels);

		if (err)

			return err;

			goto err_cancel_selq;

	}



	root = mlx5e_sw_node_create_root(priv);
@@ -524,6 +526,9 @@ int mlx5e_htb_root_add(struct mlx5e_priv *priv, u16 htb_maj_id, u16 htb_defcls, 
	 */

	smp_store_release(&priv->htb.maj_id, htb_maj_id);



	if (opened)

		mlx5e_selq_apply(&priv->selq);



	return 0;



err_sw_node_delete:
@@ -532,6 +537,8 @@ int mlx5e_htb_root_add(struct mlx5e_priv *priv, u16 htb_maj_id, u16 htb_defcls, 
err_free_queues:

	if (opened)

		mlx5e_qos_close_all_queues(&priv->channels);

err_cancel_selq:

	mlx5e_selq_cancel(&priv->selq);

	return err;

}
@@ -542,6 +549,9 @@ int mlx5e_htb_root_del(struct mlx5e_priv *priv) 


	qos_dbg(priv->mdev, "TC_HTB_DESTROY\n");



	mlx5e_selq_prepare(&priv->selq, &priv->channels.params, false);

	mlx5e_selq_apply(&priv->selq);



	WRITE_ONCE(priv->htb.maj_id, 0);

	synchronize_rcu(); /* Sync with mlx5e_select_htb_queue and TX data path. */

drivers/net/ethernet/mellanox/mlx5/core/en/selq.c

0 → 100644
+95 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB

/* Copyright (c) 2021, NVIDIA CORPORATION & AFFILIATES. All rights reserved. */



#include "selq.h"

#include <linux/slab.h>

#include <linux/netdevice.h>

#include "en.h"



struct mlx5e_selq_params {

	unsigned int num_regular_queues;

	unsigned int num_channels;

	unsigned int num_tcs;

	bool is_htb;

	bool is_ptp;

};



int mlx5e_selq_init(struct mlx5e_selq *selq, struct mutex *state_lock)

{

	struct mlx5e_selq_params *init_params;



	selq->state_lock = state_lock;



	selq->standby = kvzalloc(sizeof(*selq->standby), GFP_KERNEL);

	if (!selq->standby)

		return -ENOMEM;



	init_params = kvzalloc(sizeof(*selq->active), GFP_KERNEL);

	if (!init_params) {

		kvfree(selq->standby);

		selq->standby = NULL;

		return -ENOMEM;

	}

	/* Assign dummy values, so that mlx5e_select_queue won't crash. */

	*init_params = (struct mlx5e_selq_params) {

		.num_regular_queues = 1,

		.num_channels = 1,

		.num_tcs = 1,

		.is_htb = false,

		.is_ptp = false,

	};

	rcu_assign_pointer(selq->active, init_params);



	return 0;

}



void mlx5e_selq_cleanup(struct mlx5e_selq *selq)

{

	WARN_ON_ONCE(selq->is_prepared);



	kvfree(selq->standby);

	selq->standby = NULL;

	selq->is_prepared = true;



	mlx5e_selq_apply(selq);



	kvfree(selq->standby);

	selq->standby = NULL;

}



void mlx5e_selq_prepare(struct mlx5e_selq *selq, struct mlx5e_params *params, bool htb)

{

	lockdep_assert_held(selq->state_lock);

	WARN_ON_ONCE(selq->is_prepared);



	selq->is_prepared = true;



	selq->standby->num_channels = params->num_channels;

	selq->standby->num_tcs = mlx5e_get_dcb_num_tc(params);

	selq->standby->num_regular_queues =

		selq->standby->num_channels * selq->standby->num_tcs;

	selq->standby->is_htb = htb;

	selq->standby->is_ptp = MLX5E_GET_PFLAG(params, MLX5E_PFLAG_TX_PORT_TS);

}



void mlx5e_selq_apply(struct mlx5e_selq *selq)

{

	struct mlx5e_selq_params *old_params;



	WARN_ON_ONCE(!selq->is_prepared);



	selq->is_prepared = false;



	old_params = rcu_replace_pointer(selq->active, selq->standby,

					 lockdep_is_held(selq->state_lock));

	synchronize_net(); /* Wait until ndo_select_queue starts emitting correct values. */

	selq->standby = old_params;

}



void mlx5e_selq_cancel(struct mlx5e_selq *selq)

{

	lockdep_assert_held(selq->state_lock);

	WARN_ON_ONCE(!selq->is_prepared);



	selq->is_prepared = false;

}

drivers/net/ethernet/mellanox/mlx5/core/en/selq.h

0 → 100644
+26 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB */

/* Copyright (c) 2021, NVIDIA CORPORATION & AFFILIATES. All rights reserved. */



#ifndef __MLX5_EN_SELQ_H__

#define __MLX5_EN_SELQ_H__



#include <linux/kernel.h>



struct mlx5e_selq_params;



struct mlx5e_selq {

	struct mlx5e_selq_params __rcu *active;

	struct mlx5e_selq_params *standby;

	struct mutex *state_lock; /* points to priv->state_lock */

	bool is_prepared;

};



struct mlx5e_params;



int mlx5e_selq_init(struct mlx5e_selq *selq, struct mutex *state_lock);

void mlx5e_selq_cleanup(struct mlx5e_selq *selq);

void mlx5e_selq_prepare(struct mlx5e_selq *selq, struct mlx5e_params *params, bool htb);

void mlx5e_selq_apply(struct mlx5e_selq *selq);

void mlx5e_selq_cancel(struct mlx5e_selq *selq);



#endif /* __MLX5_EN_SELQ_H__ */