Date: Sat, 19 Aug 2023 19:21:44 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Petr Pavlu <petr.pavlu@...e.com>
Cc: tariqt@...dia.com, yishaih@...dia.com, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	jgg@...pe.ca, netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 03/10] mlx4: Replace the mlx4_interface.event
 callback with a notifier

On Sat, Aug 19, 2023 at 11:19:56AM +0200, Petr Pavlu wrote:
> On 8/13/23 18:54, Leon Romanovsky wrote:
> > On Sun, Aug 13, 2023 at 04:51:20PM +0200, Petr Pavlu wrote:
> >> Use a notifier to implement mlx4_dispatch_event() in preparation to
> >> switch mlx4_en and mlx4_ib to be an auxiliary device.
> >>
> >> A problem is that if the mlx4_interface.event callback was replaced with
> >> something as mlx4_adrv.event then the implementation of
> >> mlx4_dispatch_event() would need to acquire a lock on a given device
> >> before executing this callback. That is necessary because otherwise
> >> there is no guarantee that the associated driver cannot get unbound when
> >> the callback is running. However, taking this lock is not possible
> >> because mlx4_dispatch_event() can be invoked from the hardirq context.
> >> Using an atomic notifier allows the driver to accurately record when it
> >> wants to receive these events and solves this problem.
> >>
> >> A handler registration is done by both mlx4_en and mlx4_ib at the end of
> >> their mlx4_interface.add callback. This matches the current situation
> >> when mlx4_add_device() would enable events for a given device
> >> immediately after this callback, by adding the device on the
> >> mlx4_priv.list.
> >>
> >> Signed-off-by: Petr Pavlu <petr.pavlu@...e.com>
> >> Tested-by: Leon Romanovsky <leonro@...dia.com>
> >> Acked-by: Tariq Toukan <tariqt@...dia.com>
> >> ---
> >>  drivers/infiniband/hw/mlx4/main.c            | 41 +++++++++++++-------
> >>  drivers/infiniband/hw/mlx4/mlx4_ib.h         |  2 +
> >>  drivers/net/ethernet/mellanox/mlx4/en_main.c | 27 +++++++++----
> >>  drivers/net/ethernet/mellanox/mlx4/intf.c    | 24 ++++++++----
> >>  drivers/net/ethernet/mellanox/mlx4/main.c    |  2 +
> >>  drivers/net/ethernet/mellanox/mlx4/mlx4.h    |  2 +
> >>  drivers/net/ethernet/mellanox/mlx4/mlx4_en.h |  2 +
> >>  include/linux/mlx4/driver.h                  |  8 +++-
> >>  8 files changed, 77 insertions(+), 31 deletions(-)
> >>
> >> diff --git a/drivers/infiniband/hw/mlx4/main.c b/drivers/infiniband/hw/mlx4/main.c
> >> index 7dd70d778b6b..0761c465120b 100644
> >> --- a/drivers/infiniband/hw/mlx4/main.c
> >> +++ b/drivers/infiniband/hw/mlx4/main.c
> >> @@ -82,6 +82,8 @@ static const char mlx4_ib_version[] =
> >>  static void do_slave_init(struct mlx4_ib_dev *ibdev, int slave, int do_init);
> >>  static enum rdma_link_layer mlx4_ib_port_link_layer(struct ib_device *device,
> >>  						    u32 port_num);
> >> +static int mlx4_ib_event(struct notifier_block *this, unsigned long event,
> >> +			 void *ptr);
> >>  
> >>  static struct workqueue_struct *wq;
> >>  
> >> @@ -2836,6 +2838,12 @@ static void *mlx4_ib_add(struct mlx4_dev *dev)
> >>  				do_slave_init(ibdev, j, 1);
> >>  		}
> >>  	}
> >> +
> >> +	/* register mlx4 core notifier */
> >> +	ibdev->mlx_nb.notifier_call = mlx4_ib_event;
> >> +	err = mlx4_register_event_notifier(dev, &ibdev->mlx_nb);
> >> +	WARN(err, "failed to register mlx4 event notifier (%d)", err);
> >> +
> >>  	return ibdev;
> >>  
> >>  err_notif:
> >> @@ -2953,6 +2961,8 @@ static void mlx4_ib_remove(struct mlx4_dev *dev, void *ibdev_ptr)
> >>  	int p;
> >>  	int i;
> >>  
> >> +	mlx4_unregister_event_notifier(dev, &ibdev->mlx_nb);
> >> +
> >>  	mlx4_foreach_port(i, dev, MLX4_PORT_TYPE_IB)
> >>  		devlink_port_type_clear(mlx4_get_devlink_port(dev, i));
> >>  	ibdev->ib_active = false;
> >> @@ -3173,11 +3183,14 @@ void mlx4_sched_ib_sl2vl_update_work(struct mlx4_ib_dev *ibdev,
> >>  	}
> >>  }
> >>  
> >> -static void mlx4_ib_event(struct mlx4_dev *dev, void *ibdev_ptr,
> >> -			  enum mlx4_dev_event event, unsigned long param)
> >> +static int mlx4_ib_event(struct notifier_block *this, unsigned long event,
> >> +			 void *ptr)
> >>  {
> >> +	struct mlx4_ib_dev *ibdev =
> >> +		container_of(this, struct mlx4_ib_dev, mlx_nb);
> >> +	struct mlx4_dev *dev = ibdev->dev;
> >> +	unsigned long param = *(unsigned long *)ptr;
> > 
> > You don't need this assignment here as later, you will cast param again,
> > in your next patches:
> > 
> >   3227         if (event == MLX4_DEV_EVENT_PORT_MGMT_CHANGE)
> >   3228                 eqe = (struct mlx4_eqe *)param;
> >   3229         else
> >   3230                 p = (int) param;
> > 
> > so use ptr directly:
> > 
> >          if (event == MLX4_DEV_EVENT_PORT_MGMT_CHANGE)
> >                  eqe = param;
> >          else
> >                  p = *(int *) param;
> 
> Function mlx4_dispatch_event() currently takes an 'unsigned long' as its
> event parameter. The patch updates the function to use
> atomic_notifier_call_chain() which however expects 'void *' as the
> 'param' value. To solve the mismatch, mlx4_dispatch_event() passes to
> atomic_notifier_call_chain() an address of the original 'param'. This
> creates one additional level of indirection which the handlers, such as
> mlx4_ib_event(), need to deal with. Line
> 'unsigned long param = *(unsigned long *)ptr;' is added for that.
> 
> I think the best way to avoid this complexity would be for
> mlx4_dispatch_event() to take 'void *' as its 'param' in the first
> place. I would add the following patch before this one in v3 of the
> series.


Looks good to me.

Thanks.

> 
> 
> From e17d6b8fb32e6caeba2929764ad0249a2e136049 Mon Sep 17 00:00:00 2001
> From: Petr Pavlu <petr.pavlu@...e.com>
> Date: Fri, 18 Aug 2023 12:55:30 +0200
> Subject: [PATCH] mlx4: Use 'void *' as the event param of
>  mlx4_dispatch_event()
> 
> Function mlx4_dispatch_event() takes an 'unsigned long' as its event
> parameter. The actual value is none (MLX4_DEV_EVENT_CATASTROPHIC_ERROR),
> a pointer to mlx4_eqe (MLX4_DEV_EVENT_PORT_MGMT_CHANGE), or a 32-bit
> integer (remaining events).
> 
> In preparation to switch mlx4_en and mlx4_ib to be an auxiliary device,
> the mlx4_interface.event callback is replaced with a notifier and
> function mlx4_dispatch_event() gets updated to invoke
> atomic_notifier_call_chain(). This requires forwarding the input 'param'
> value from the former function to the latter. A problem is that the
> notifier call takes 'void *' as its 'param' value, compared to
> 'unsigned long' used by mlx4_dispatch_event(). Re-passing the value
> would need either punning it to 'void *' or passing down the address of
> the input 'param'. Both approaches create a number of unnecessary casts.
> 
> Change instead the input 'param' of mlx4_dispatch_event() from
> 'unsigned long' to 'void *'. A mlx4_eqe pointer can be passed directly,
> callers using an int value are adjusted to pass its address.
> 
> Signed-off-by: Petr Pavlu <petr.pavlu@...e.com>
> ---
>  drivers/infiniband/hw/mlx4/main.c            | 14 ++++++++++----
>  drivers/net/ethernet/mellanox/mlx4/catas.c   |  2 +-
>  drivers/net/ethernet/mellanox/mlx4/cmd.c     |  4 ++--
>  drivers/net/ethernet/mellanox/mlx4/en_main.c | 17 +++++++++++++++--
>  drivers/net/ethernet/mellanox/mlx4/eq.c      | 15 ++++++++-------
>  drivers/net/ethernet/mellanox/mlx4/intf.c    |  2 +-
>  drivers/net/ethernet/mellanox/mlx4/mlx4.h    |  2 +-
>  include/linux/mlx4/driver.h                  |  2 +-
>  8 files changed, 39 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/mlx4/main.c b/drivers/infiniband/hw/mlx4/main.c
> index 7dd70d778b6b..2c5fd8174b3c 100644
> --- a/drivers/infiniband/hw/mlx4/main.c
> +++ b/drivers/infiniband/hw/mlx4/main.c
> @@ -3174,7 +3174,7 @@ void mlx4_sched_ib_sl2vl_update_work(struct mlx4_ib_dev *ibdev,
>  }
>  
>  static void mlx4_ib_event(struct mlx4_dev *dev, void *ibdev_ptr,
> -			  enum mlx4_dev_event event, unsigned long param)
> +			  enum mlx4_dev_event event, void *param)
>  {
>  	struct ib_event ibev;
>  	struct mlx4_ib_dev *ibdev = to_mdev((struct ib_device *) ibdev_ptr);
> @@ -3194,10 +3194,16 @@ static void mlx4_ib_event(struct mlx4_dev *dev, void *ibdev_ptr,
>  		return;
>  	}
>  
> -	if (event == MLX4_DEV_EVENT_PORT_MGMT_CHANGE)
> +	switch (event) {
> +	case MLX4_DEV_EVENT_CATASTROPHIC_ERROR:
> +		break;
> +	case MLX4_DEV_EVENT_PORT_MGMT_CHANGE:
>  		eqe = (struct mlx4_eqe *)param;
> -	else
> -		p = (int) param;
> +		break;
> +	default:
> +		p = *(int *)param;
> +		break;
> +	}
>  
>  	switch (event) {
>  	case MLX4_DEV_EVENT_PORT_UP:
> diff --git a/drivers/net/ethernet/mellanox/mlx4/catas.c b/drivers/net/ethernet/mellanox/mlx4/catas.c
> index 0eb7b83637d8..0d8a362c2673 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/catas.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/catas.c
> @@ -194,7 +194,7 @@ void mlx4_enter_error_state(struct mlx4_dev_persistent *persist)
>  	mutex_unlock(&persist->device_state_mutex);
>  
>  	/* At that step HW was already reset, now notify clients */
> -	mlx4_dispatch_event(dev, MLX4_DEV_EVENT_CATASTROPHIC_ERROR, 0);
> +	mlx4_dispatch_event(dev, MLX4_DEV_EVENT_CATASTROPHIC_ERROR, NULL);
>  	mlx4_cmd_wake_completions(dev);
>  	return;
>  
> diff --git a/drivers/net/ethernet/mellanox/mlx4/cmd.c b/drivers/net/ethernet/mellanox/mlx4/cmd.c
> index c56d2194cbfc..f5b1f8c7834f 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/cmd.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/cmd.c
> @@ -2113,7 +2113,7 @@ static void mlx4_master_do_cmd(struct mlx4_dev *dev, int slave, u8 cmd,
>  		if (MLX4_COMM_CMD_FLR == slave_state[slave].last_cmd)
>  			goto inform_slave_state;
>  
> -		mlx4_dispatch_event(dev, MLX4_DEV_EVENT_SLAVE_SHUTDOWN, slave);
> +		mlx4_dispatch_event(dev, MLX4_DEV_EVENT_SLAVE_SHUTDOWN, &slave);
>  
>  		/* write the version in the event field */
>  		reply |= mlx4_comm_get_version();
> @@ -2152,7 +2152,7 @@ static void mlx4_master_do_cmd(struct mlx4_dev *dev, int slave, u8 cmd,
>  		if (mlx4_master_activate_admin_state(priv, slave))
>  				goto reset_slave;
>  		slave_state[slave].active = true;
> -		mlx4_dispatch_event(dev, MLX4_DEV_EVENT_SLAVE_INIT, slave);
> +		mlx4_dispatch_event(dev, MLX4_DEV_EVENT_SLAVE_INIT, &slave);
>  		break;
>  	case MLX4_COMM_CMD_VHCR_POST:
>  		if ((slave_state[slave].last_cmd != MLX4_COMM_CMD_VHCR_EN) &&
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_main.c b/drivers/net/ethernet/mellanox/mlx4/en_main.c
> index be8ba34c9025..83dae886ade6 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_main.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_main.c
> @@ -184,10 +184,22 @@ static void mlx4_en_get_profile(struct mlx4_en_dev *mdev)
>  }
>  
>  static void mlx4_en_event(struct mlx4_dev *dev, void *endev_ptr,
> -			  enum mlx4_dev_event event, unsigned long port)
> +			  enum mlx4_dev_event event, void *param)
>  {
>  	struct mlx4_en_dev *mdev = (struct mlx4_en_dev *) endev_ptr;
>  	struct mlx4_en_priv *priv;
> +	int port;
> +
> +	switch (event) {
> +	case MLX4_DEV_EVENT_CATASTROPHIC_ERROR:
> +	case MLX4_DEV_EVENT_PORT_MGMT_CHANGE:
> +	case MLX4_DEV_EVENT_SLAVE_INIT:
> +	case MLX4_DEV_EVENT_SLAVE_SHUTDOWN:
> +		break;
> +	default:
> +		port = *(int *)param;
> +		break;
> +	}
>  
>  	switch (event) {
>  	case MLX4_DEV_EVENT_PORT_UP:
> @@ -205,6 +217,7 @@ static void mlx4_en_event(struct mlx4_dev *dev, void *endev_ptr,
>  		mlx4_err(mdev, "Internal error detected, restarting device\n");
>  		break;
>  
> +	case MLX4_DEV_EVENT_PORT_MGMT_CHANGE:
>  	case MLX4_DEV_EVENT_SLAVE_INIT:
>  	case MLX4_DEV_EVENT_SLAVE_SHUTDOWN:
>  		break;
> @@ -213,7 +226,7 @@ static void mlx4_en_event(struct mlx4_dev *dev, void *endev_ptr,
>  		    !mdev->pndev[port])
>  			return;
>  		mlx4_warn(mdev, "Unhandled event %d for port %d\n", event,
> -			  (int) port);
> +			  port);
>  	}
>  }
>  
> diff --git a/drivers/net/ethernet/mellanox/mlx4/eq.c b/drivers/net/ethernet/mellanox/mlx4/eq.c
> index 414e390e6b48..6598b10a9ff4 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/eq.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/eq.c
> @@ -501,7 +501,7 @@ static int mlx4_eq_int(struct mlx4_dev *dev, struct mlx4_eq *eq)
>  	int port;
>  	int slave = 0;
>  	int ret;
> -	u32 flr_slave;
> +	int flr_slave;
>  	u8 update_slave_state;
>  	int i;
>  	enum slave_port_gen_event gen_event;
> @@ -606,8 +606,8 @@ static int mlx4_eq_int(struct mlx4_dev *dev, struct mlx4_eq *eq)
>  			port = be32_to_cpu(eqe->event.port_change.port) >> 28;
>  			slaves_port = mlx4_phys_to_slaves_pport(dev, port);
>  			if (eqe->subtype == MLX4_PORT_CHANGE_SUBTYPE_DOWN) {
> -				mlx4_dispatch_event(dev, MLX4_DEV_EVENT_PORT_DOWN,
> -						    port);
> +				mlx4_dispatch_event(
> +					dev, MLX4_DEV_EVENT_PORT_DOWN, &port);
>  				mlx4_priv(dev)->sense.do_sense_port[port] = 1;
>  				if (!mlx4_is_master(dev))
>  					break;
> @@ -647,7 +647,8 @@ static int mlx4_eq_int(struct mlx4_dev *dev, struct mlx4_eq *eq)
>  					}
>  				}
>  			} else {
> -				mlx4_dispatch_event(dev, MLX4_DEV_EVENT_PORT_UP, port);
> +				mlx4_dispatch_event(dev, MLX4_DEV_EVENT_PORT_UP,
> +						    &port);
>  
>  				mlx4_priv(dev)->sense.do_sense_port[port] = 0;
>  
> @@ -758,7 +759,7 @@ static int mlx4_eq_int(struct mlx4_dev *dev, struct mlx4_eq *eq)
>  			}
>  			spin_unlock_irqrestore(&priv->mfunc.master.slave_state_lock, flags);
>  			mlx4_dispatch_event(dev, MLX4_DEV_EVENT_SLAVE_SHUTDOWN,
> -					    flr_slave);
> +					    &flr_slave);
>  			queue_work(priv->mfunc.master.comm_wq,
>  				   &priv->mfunc.master.slave_flr_event_work);
>  			break;
> @@ -787,8 +788,8 @@ static int mlx4_eq_int(struct mlx4_dev *dev, struct mlx4_eq *eq)
>  			break;
>  
>  		case MLX4_EVENT_TYPE_PORT_MNG_CHG_EVENT:
> -			mlx4_dispatch_event(dev, MLX4_DEV_EVENT_PORT_MGMT_CHANGE,
> -					    (unsigned long) eqe);
> +			mlx4_dispatch_event(
> +				dev, MLX4_DEV_EVENT_PORT_MGMT_CHANGE, eqe);
>  			break;
>  
>  		case MLX4_EVENT_TYPE_RECOVERABLE_ERROR_EVENT:
> diff --git a/drivers/net/ethernet/mellanox/mlx4/intf.c b/drivers/net/ethernet/mellanox/mlx4/intf.c
> index 28d7da925d36..a761971cd0c4 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/intf.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/intf.c
> @@ -180,7 +180,7 @@ int mlx4_do_bond(struct mlx4_dev *dev, bool enable)
>  }
>  
>  void mlx4_dispatch_event(struct mlx4_dev *dev, enum mlx4_dev_event type,
> -			 unsigned long param)
> +			 void *param)
>  {
>  	struct mlx4_priv *priv = mlx4_priv(dev);
>  	struct mlx4_device_context *dev_ctx;
> diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4.h b/drivers/net/ethernet/mellanox/mlx4/mlx4.h
> index 6ccf340660d9..de5699a4ddaa 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/mlx4.h
> +++ b/drivers/net/ethernet/mellanox/mlx4/mlx4.h
> @@ -1048,7 +1048,7 @@ int mlx4_restart_one(struct pci_dev *pdev);
>  int mlx4_register_device(struct mlx4_dev *dev);
>  void mlx4_unregister_device(struct mlx4_dev *dev);
>  void mlx4_dispatch_event(struct mlx4_dev *dev, enum mlx4_dev_event type,
> -			 unsigned long param);
> +			 void *param);
>  
>  struct mlx4_dev_cap;
>  struct mlx4_init_hca_param;
> diff --git a/include/linux/mlx4/driver.h b/include/linux/mlx4/driver.h
> index 923951e19300..032d7f5bfef6 100644
> --- a/include/linux/mlx4/driver.h
> +++ b/include/linux/mlx4/driver.h
> @@ -58,7 +58,7 @@ struct mlx4_interface {
>  	void *			(*add)	 (struct mlx4_dev *dev);
>  	void			(*remove)(struct mlx4_dev *dev, void *context);
>  	void			(*event) (struct mlx4_dev *dev, void *context,
> -					  enum mlx4_dev_event event, unsigned long param);
> +					  enum mlx4_dev_event event, void *param);
>  	void			(*activate)(struct mlx4_dev *dev, void *context);
>  	struct list_head	list;
>  	enum mlx4_protocol	protocol;
> -- 
> 2.35.3
> 

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