NAK: [SRU][Yakkety][PATCH 1/1] net/mlx4_core: Avoid delays during VF driver device shutdown

[Thadeu Lima de Souza Cascardo]

On Thu, Mar 30, 2017 at 04:35:59PM -0400, Joseph Salisbury wrote:
> From: Jack Morgenstein <jackm at dev.mellanox.co.il>
> 
> BugLink: http://bugs.launchpad.net/bugs/1672785
> 
> Some Hypervisors detach VFs from VMs by instantly causing an FLR event
> to be generated for a VF.
> 
> In the mlx4 case, this will cause that VF's comm channel to be disabled
> before the VM has an opportunity to invoke the VF device's "shutdown"
> method.
> 
> For such Hypervisors, there is a race condition between the VF's
> shutdown method and its internal-error detection/reset thread.
> 
> The internal-error detection/reset thread (which runs every 5 seconds) also
> detects a disabled comm channel. If the internal-error detection/reset
> flow wins the race, we still get delays (while that flow tries repeatedly
> to detect comm-channel recovery).
> 
> The cited commit fixed the command timeout problem when the
> internal-error detection/reset flow loses the race.
> 
> This commit avoids the unneeded delays when the internal-error
> detection/reset flow wins.
> 
> Fixes: d585df1c5ccf ("net/mlx4_core: Avoid command timeouts during VF driver device shutdown")
> Signed-off-by: Jack Morgenstein <jackm at dev.mellanox.co.il>
> Reported-by: Simon Xiao <sixiao at microsoft.com>
> Signed-off-by: Tariq Toukan <tariqt at mellanox.com>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> (backported from commit 4cbe4dac82e423ecc9a0ba46af24a860853259f4)
> Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
> ---
>  drivers/net/ethernet/mellanox/mlx4/cmd.c  | 11 +++++++++++
>  drivers/net/ethernet/mellanox/mlx4/main.c | 11 +++++++++++
>  include/linux/mlx4/device.h               |  1 +
>  3 files changed, 23 insertions(+)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/cmd.c b/drivers/net/ethernet/mellanox/mlx4/cmd.c
> index f04a423..be6906b 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/cmd.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/cmd.c
> @@ -2278,6 +2278,17 @@ static int sync_toggles(struct mlx4_dev *dev)
>  		rd_toggle = swab32(readl(&priv->mfunc.comm->slave_read));
>  		if (wr_toggle == 0xffffffff || rd_toggle == 0xffffffff) {
>  			/* PCI might be offline */
> +
> +			/* If device removal has been requested,
> +			 * do not continue retrying.
> +			 */
> +			if (dev->persist->interface_state &
> +			    MLX4_INTERFACE_STATE_NOWAIT) {
> +				mlx4_warn(dev,
> +					  "communication channel is offline\n");
> +				return -EIO;
> +			}
> +
>  			msleep(100);
>  			wr_toggle = swab32(readl(&priv->mfunc.comm->
>  					   slave_write));
> diff --git a/drivers/net/ethernet/mellanox/mlx4/main.c b/drivers/net/ethernet/mellanox/mlx4/main.c
> index 7183ac4..ea5e362 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/main.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/main.c
> @@ -1916,6 +1916,14 @@ static int mlx4_comm_check_offline(struct mlx4_dev *dev)
>  			       (u32)(1 << COMM_CHAN_OFFLINE_OFFSET));
>  		if (!offline_bit)
>  			return 0;
> +
> +		/* If device removal has been requested,
> +		 * do not continue retrying.
> +		 */
> +		if (dev->persist->interface_state &
> +		    MLX4_INTERFACE_STATE_NOWAIT)
> +			break;
> +
>  		/* There are cases as part of AER/Reset flow that PF needs
>  		 * around 100 msec to load. We therefore sleep for 100 msec
>  		 * to allow other tasks to make use of that CPU during this
> @@ -3930,6 +3938,9 @@ static void mlx4_remove_one(struct pci_dev *pdev)
>  	struct devlink *devlink = priv_to_devlink(priv);
>  	int active_vfs = 0;
>  
> +	if (mlx4_is_slave(dev))
> +		persist->interface_state |= MLX4_INTERFACE_STATE_NOWAIT;
> +
>  	mutex_lock(&persist->interface_state_mutex);
>  	persist->interface_state |= MLX4_INTERFACE_STATE_DELETION;
>  	mutex_unlock(&persist->interface_state_mutex);
> diff --git a/include/linux/mlx4/device.h b/include/linux/mlx4/device.h
> index 42da355..d49f11d 100644
> --- a/include/linux/mlx4/device.h
> +++ b/include/linux/mlx4/device.h
> @@ -468,6 +468,7 @@ enum {
>  	MLX4_INTERFACE_STATE_UP		= 1 << 0,
>  	MLX4_INTERFACE_STATE_DELETION	= 1 << 1,
>  	MLX4_INTERFACE_STATE_SHUTDOWN	= 1 << 2,
> +	MLX4_INTERFACE_STATE_NOWAIT	= 1 << 2,

So, NOWAIT and SHUTDOWN are defined to the same value, so it might be
necessary to review it that is going to work as expected. Maybe doing
the shutdown removal is a path to consider (commit
b4353708f5a1c084fd73f1b6fd243b142157b173).

Cascardo.

>  };
>  
>  #define MSTR_SM_CHANGE_MASK (MLX4_EQ_PORT_INFO_MSTR_SM_SL_CHANGE_MASK | \
> -- 
> 2.7.4
> 
> 
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