Re: [PATCH v1 1/2] vdpa/mlx5: Support creating resources with uid == 0

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, May 31, 2021 at 07:04:04PM +0300, Eli Cohen wrote:
> Currently all resources must be created with uid != 0 which is essential
> when userspace processes are allocating virtquueue resources. Since this
> is a kernel implementation, it is perfectly legal to open resources with
> uid == 0.
> 
> In case firmware supports, avoid allocating user context.
> 
> Signed-off-by: Eli Cohen <elic@nvidia.com>
> ---
> v0 --> v1:
>   Fix typo and modify phrasing

threading's broken now

>  drivers/vdpa/mlx5/core/resources.c | 6 ++++++
>  include/linux/mlx5/mlx5_ifc.h      | 4 +++-
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vdpa/mlx5/core/resources.c b/drivers/vdpa/mlx5/core/resources.c
> index 6521cbd0f5c2..836ab9ef0fa6 100644
> --- a/drivers/vdpa/mlx5/core/resources.c
> +++ b/drivers/vdpa/mlx5/core/resources.c
> @@ -54,6 +54,9 @@ static int create_uctx(struct mlx5_vdpa_dev *mvdev, u16 *uid)
>  	void *in;
>  	int err;
>  
> +	if (MLX5_CAP_GEN(mvdev->mdev, umem_uid_0))
> +		return 0;
> +
>  	/* 0 means not supported */
>  	if (!MLX5_CAP_GEN(mvdev->mdev, log_max_uctx))
>  		return -EOPNOTSUPP;
> @@ -79,6 +82,9 @@ static void destroy_uctx(struct mlx5_vdpa_dev *mvdev, u32 uid)
>  	u32 out[MLX5_ST_SZ_DW(destroy_uctx_out)] = {};
>  	u32 in[MLX5_ST_SZ_DW(destroy_uctx_in)] = {};
>  
> +	if (!uid)
> +		return;
> +
>  	MLX5_SET(destroy_uctx_in, in, opcode, MLX5_CMD_OP_DESTROY_UCTX);
>  	MLX5_SET(destroy_uctx_in, in, uid, uid);
>  
> diff --git a/include/linux/mlx5/mlx5_ifc.h b/include/linux/mlx5/mlx5_ifc.h
> index 9c68b2da14c6..606d2aeacad4 100644
> --- a/include/linux/mlx5/mlx5_ifc.h
> +++ b/include/linux/mlx5/mlx5_ifc.h
> @@ -1487,7 +1487,9 @@ struct mlx5_ifc_cmd_hca_cap_bits {
>  	u8         uar_4k[0x1];
>  	u8         reserved_at_241[0x9];
>  	u8         uar_sz[0x6];
> -	u8         reserved_at_250[0x8];
> +	u8         reserved_at_248[0x2];
> +	u8         umem_uid_0[0x1];
> +	u8         reserved_at_250[0x5];
>  	u8         log_pg_sz[0x8];
>  
>  	u8         bf[0x1];
> -- 
> 2.31.1