Re: [PATCH v2] vdpa/mlx5: Allow CVQ size changes

[Lei Yang]

QE tested this patch's V2, qemu no longer print error messages
"qemu-system-x86_64: Insufficient written data (0)" after
enable/disable multi queues multi times inside guest. Both "x-svq=on
'' and without it are all test pass.

Tested-by: Lei Yang <leiyang@xxxxxxxxxx>

On Fri, Feb 16, 2024 at 10:25 PM Jonah Palmer <jonah.palmer@xxxxxxxxxx> wrote:
>
> The MLX driver was not updating its control virtqueue size at set_vq_num
> and instead always initialized to MLX5_CVQ_MAX_ENT (16) at
> setup_cvq_vring.
>
> Qemu would try to set the size to 64 by default, however, because the
> CVQ size always was initialized to 16, an error would be thrown when
> sending >16 control messages (as used-ring entry 17 is initialized to 0).
> For example, starting a guest with x-svq=on and then executing the
> following command would produce the error below:
>
>  # for i in {1..20}; do ifconfig eth0 hw ether XX:xx:XX:xx:XX:XX; done
>
>  qemu-system-x86_64: Insufficient written data (0)
>  [  435.331223] virtio_net virtio0: Failed to set mac address by vq command.
>  SIOCSIFHWADDR: Invalid argument
>
> Acked-by: Dragos Tatulea <dtatulea@xxxxxxxxxx>
> Acked-by: Eugenio Pérez <eperezma@xxxxxxxxxx>
> Signed-off-by: Jonah Palmer <jonah.palmer@xxxxxxxxxx>
> ---
>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 778821bab7d9..ecfc16151d61 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -151,8 +151,6 @@ static void teardown_driver(struct mlx5_vdpa_net *ndev);
>
>  static bool mlx5_vdpa_debug;
>
> -#define MLX5_CVQ_MAX_ENT 16
> -
>  #define MLX5_LOG_VIO_FLAG(_feature)                                                                \
>         do {                                                                                       \
>                 if (features & BIT_ULL(_feature))                                                  \
> @@ -2276,9 +2274,16 @@ static void mlx5_vdpa_set_vq_num(struct vdpa_device *vdev, u16 idx, u32 num)
>         struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
>         struct mlx5_vdpa_virtqueue *mvq;
>
> -       if (!is_index_valid(mvdev, idx) || is_ctrl_vq_idx(mvdev, idx))
> +       if (!is_index_valid(mvdev, idx))
>                 return;
>
> +        if (is_ctrl_vq_idx(mvdev, idx)) {
> +                struct mlx5_control_vq *cvq = &mvdev->cvq;
> +
> +                cvq->vring.vring.num = num;
> +                return;
> +        }
> +
>         mvq = &ndev->vqs[idx];
>         mvq->num_ent = num;
>  }
> @@ -2963,7 +2968,7 @@ static int setup_cvq_vring(struct mlx5_vdpa_dev *mvdev)
>                 u16 idx = cvq->vring.last_avail_idx;
>
>                 err = vringh_init_iotlb(&cvq->vring, mvdev->actual_features,
> -                                       MLX5_CVQ_MAX_ENT, false,
> +                                       cvq->vring.vring.num, false,
>                                         (struct vring_desc *)(uintptr_t)cvq->desc_addr,
>                                         (struct vring_avail *)(uintptr_t)cvq->driver_addr,
>                                         (struct vring_used *)(uintptr_t)cvq->device_addr);
> --
> 2.39.3
>