Re: [PATCH v9 0/2] IB/mlx5: Fix loopback rollback and locking

Re: [PATCH v9 0/2] IB/mlx5: Fix loopback rollback and locking

[Leon Romanovsky]

On Fri, Apr 10, 2026 at 01:52:16AM +0100, Prathamesh Deshpande wrote:
> This series fixes transport-domain rollback and loopback state
> consistency in mlx5 IB.
> 
> Patch 1 fixes TD rollback on mlx5_ib_enable_lb() failure, makes the
> success return path explicit, and initializes lb.mutex earlier.
> 
> Patch 2 serializes MP force-enable state updates with lb.mutex and
> implements capability-aware thresholds (td_base) to ensure correct
> loopback behavior on both TD-capable and no-TD hardware.
> 
> v9:
> - Address race/state issues around force_enable and enabled.
> - Fix TD leak on failure after successful allocation.
> - Implement hardware-aware thresholds via mlx5_ib_lb_td_base() to
>   handle both TD-capable and no-TD hardware correctly.
> - Serialize MP force-enable transitions under lb.mutex.
> 
> v8:
> - Resubmitted as a fresh, independent thread per maintainer request.
> - No functional changes since v7.
> 
> v7:
> - Split the series into two patches to isolate the return-value/mutex 
>   initialization fix from the refcounting logic.
> - Moved force_enable check after increments/decrements to fix leaks.
> - Updated hardware disable condition to a strict zero-check.
> 
> v1-v6:
> - Initial combined versions.
> - Added deallocation of tdn on failure.
> - Moved mutex_init to stage_init_init to prevent crashes on non-ETH.
> - Implemented atomic rollback in enable/disable paths.
> 
> Prathamesh Deshpande (2):
>   IB/mlx5: Fix transport-domain rollback and initialize lb mutex earlier

I agree that this patch is needed.

>   IB/mlx5: Serialize force-enable state and preserve loopback accounting

This change does not appear to be justified. The commit message provides no
clear explanation of why it is needed.

Thanks

> 
>  drivers/infiniband/hw/mlx5/main.c | 81 +++++++++++++++++++++++--------
>  1 file changed, 62 insertions(+), 19 deletions(-)
> 
> -- 
> 2.43.0
> 

Re: [PATCH v9 1/2] IB/mlx5: Fix transport-domain rollback and initialize lb mutex earlier

[Leon Romanovsky]

On Fri, Apr 10, 2026 at 01:52:17AM +0100, Prathamesh Deshpande wrote:
> mlx5_ib_alloc_transport_domain() allocates a transport domain and then
> may fail in mlx5_ib_enable_lb(). In that case, the allocated TD is leaked.
> 
> Fix this by deallocating the TD when mlx5_ib_enable_lb() returns an
> error. Also return 0 explicitly in the no-loopback-capability success
> branch, and move dev->lb.mutex initialization to mlx5_ib_stage_init_init().
> 
> Fixes: 146d2f1af324 ("IB/mlx5: Allocate a Transport Domain for each ucontext")
> Signed-off-by: Prathamesh Deshpande <prathameshdeshpande7@gmail.com>
> ---
>  drivers/infiniband/hw/mlx5/main.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
> index e02bfb1479f5..6be198c0651c 100644
> --- a/drivers/infiniband/hw/mlx5/main.c
> +++ b/drivers/infiniband/hw/mlx5/main.c
> @@ -2068,9 +2068,13 @@ static int mlx5_ib_alloc_transport_domain(struct mlx5_ib_dev *dev, u32 *tdn,
>  	if ((MLX5_CAP_GEN(dev->mdev, port_type) != MLX5_CAP_PORT_TYPE_ETH) ||
>  	    (!MLX5_CAP_GEN(dev->mdev, disable_local_lb_uc) &&
>  	     !MLX5_CAP_GEN(dev->mdev, disable_local_lb_mc)))
> -		return err;
> +		return 0;
> +
> +	err = mlx5_ib_enable_lb(dev, true, false);
> +	if (err)
> +		mlx5_cmd_dealloc_transport_domain(dev->mdev, *tdn, uid);
>  
> -	return mlx5_ib_enable_lb(dev, true, false);
> +	return err;
>  }
>  
>  static void mlx5_ib_dealloc_transport_domain(struct mlx5_ib_dev *dev, u32 tdn,
> @@ -4513,6 +4517,7 @@ static int mlx5_ib_stage_init_init(struct mlx5_ib_dev *dev)
>  
>  	mutex_init(&dev->cap_mask_mutex);
>  	mutex_init(&dev->data_direct_lock);
> +	mutex_init(&dev->lb.mutex);

There is also a need to call mutex_destroy() to ensure proper resource cleanup.

Thanks

>  	INIT_LIST_HEAD(&dev->qp_list);
>  	spin_lock_init(&dev->reset_flow_resource_lock);
>  	xa_init(&dev->odp_mkeys);
> @@ -4786,11 +4791,6 @@ static int mlx5_ib_stage_caps_init(struct mlx5_ib_dev *dev)
>  	if (err)
>  		return err;
>  
> -	if ((MLX5_CAP_GEN(dev->mdev, port_type) == MLX5_CAP_PORT_TYPE_ETH) &&
> -	    (MLX5_CAP_GEN(dev->mdev, disable_local_lb_uc) ||
> -	     MLX5_CAP_GEN(dev->mdev, disable_local_lb_mc)))
> -		mutex_init(&dev->lb.mutex);
> -
>  	if (MLX5_CAP_GEN_64(dev->mdev, general_obj_types) &
>  			MLX5_GENERAL_OBJ_TYPES_CAP_VIRTIO_NET_Q) {
>  		err = mlx5_ib_init_var_region(dev);
> -- 
> 2.43.0
> 

Re: [PATCH v9 0/2] IB/mlx5: Fix loopback rollback and locking

[Prathamesh Deshpande]

On Sun, May 10, 2026 at 13:55:31 +0300, Leon Romanovsky wrote:
> On Fri, Apr 10, 2026 at 01:52:16AM +0100, Prathamesh Deshpande wrote:
> > Prathamesh Deshpande (2):
> >   IB/mlx5: Fix transport-domain rollback and initialize lb mutex earlier
> 
> I agree that this patch is needed.
> 
> >   IB/mlx5: Serialize force-enable state and preserve loopback accounting
> 
> This change does not appear to be justified. The commit message provides no
> clear explanation of why it is needed.
> 
> Thanks
 
Thanks, Leon.
 
v11 dropped the MP force-enable locking changes and kept MP helper behavior
unchanged. Patch 2 is now limited to the regular-path threshold/accounting
fixes.

I have also just sent a fresh v12 series that addresses your Patch 1 
review regarding the missing mutex cleanups. You can find the updated 
series here: https://lore.kernel.org/all/20260510222258.6654-1-prathameshdeshpande7@gmail.com/