Re: [PATCH rdma-next 5/6] RDMA/mlx5: Change check for cacheable user mkeys

[Junxian Huang <huangjunxian6@hisilicon.com>]

On 2024/1/25 20:30, Leon Romanovsky wrote:
> From: Or Har-Toov <ohartoov@nvidia.com>
> 
> In the dereg flow, UMEM is not a good enough indication whether an MR
> is from userspace since in mlx5_ib_rereg_user_mr there are some cases
> when a new MR is created and the UMEM of the old MR is set to NULL.
> Currently when mlx5_ib_dereg_mr is called on the old MR, UMEM is NULL
> but cache_ent can be different than NULL. So, the mkey will not be
> destroyed.
> Therefore checking if mkey is from user application and cacheable
> should be done by checking if rb_key or cache_ent exist and all other kind of
> mkeys should be destroyed.
> 
> Fixes: dd1b913fb0d0 ("RDMA/mlx5: Cache all user cacheable mkeys on dereg MR flow")
> Signed-off-by: Or Har-Toov <ohartoov@nvidia.com>
> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> ---
>  drivers/infiniband/hw/mlx5/mr.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
> index 12bca6ca4760..3c241898e064 100644
> --- a/drivers/infiniband/hw/mlx5/mr.c
> +++ b/drivers/infiniband/hw/mlx5/mr.c
> @@ -1857,6 +1857,11 @@ static int cache_ent_find_and_store(struct mlx5_ib_dev *dev,
>  	return ret;
>  }
>  
> +static bool is_cacheable_mkey(struct mlx5_ib_mkey mkey)

I think it's better using a pointer as the parameter instead of the struct itself.

Junxian

> +{
> +	return mkey.cache_ent || mkey.rb_key.ndescs;
> +}
> +
>  int mlx5_ib_dereg_mr(struct ib_mr *ibmr, struct ib_udata *udata)
>  {
>  	struct mlx5_ib_mr *mr = to_mmr(ibmr);
> @@ -1901,12 +1906,6 @@ int mlx5_ib_dereg_mr(struct ib_mr *ibmr, struct ib_udata *udata)
>  		mr->sig = NULL;
>  	}
>  
> -	/* Stop DMA */
> -	if (mr->umem && mlx5r_umr_can_load_pas(dev, mr->umem->length))
> -		if (mlx5r_umr_revoke_mr(mr) ||
> -		    cache_ent_find_and_store(dev, mr))
> -			mr->mmkey.cache_ent = NULL;
> -
>  	if (mr->umem && mr->umem->is_peer) {
>  		rc = mlx5r_umr_revoke_mr(mr);
>  		if (rc)
> @@ -1914,7 +1913,9 @@ int mlx5_ib_dereg_mr(struct ib_mr *ibmr, struct ib_udata *udata)
>  		ib_umem_stop_invalidation_notifier(mr->umem);
>  	}
>  
> -	if (!mr->mmkey.cache_ent) {
> +	/* Stop DMA */
> +	if (!is_cacheable_mkey(mr->mmkey) || mlx5r_umr_revoke_mr(mr) ||
> +	    cache_ent_find_and_store(dev, mr)) {
>  		rc = destroy_mkey(to_mdev(mr->ibmr.device), mr);
>  		if (rc)
>  			return rc;