Re: [PATCH vhost 21/23] vdpa/mlx5: Re-create HW VQs under certain conditions

[Eugenio Perez Martin]

On Mon, Jun 17, 2024 at 5:09 PM Dragos Tatulea <dtatulea@xxxxxxxxxx> wrote:
>
> There are a few conditions under which the hardware VQs need a full
> teardown and setup:
>
> - VQ size changed to something else than default value. Hardware VQ size
>   modification is not supported.
>
> - User turns off certain device features: mergeable buffers, checksum
>   virtio 1.0 compliance. In these cases, the TIR and RQT need to be
>   re-created.
>
> Add a needs_teardown configuration variable and set it when detecting
> the above scenarios. On next DRIVER_OK, the resources will be torn down
> first.
>
> Signed-off-by: Dragos Tatulea <dtatulea@xxxxxxxxxx>
> Reviewed-by: Cosmin Ratiu <cratiu@xxxxxxxxxx>

Acked-by: Eugenio Pérez <eperezma@xxxxxxxxxx>

> ---
>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 15 +++++++++++++++
>  drivers/vdpa/mlx5/net/mlx5_vnet.h |  1 +
>  2 files changed, 16 insertions(+)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index b2836fd3d1dd..d80d6b47da61 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -2390,6 +2390,7 @@ static void mlx5_vdpa_set_vq_num(struct vdpa_device *vdev, u16 idx, u32 num)
>          }
>
>         mvq = &ndev->vqs[idx];
> +       ndev->needs_teardown = num != mvq->num_ent;
>         mvq->num_ent = num;
>  }
>
> @@ -2800,6 +2801,7 @@ static int mlx5_vdpa_set_driver_features(struct vdpa_device *vdev, u64 features)
>         struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
>         struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
>         u64 old_features = mvdev->actual_features;
> +       u64 diff_features;
>         int err;
>
>         print_features(mvdev, features, true);
> @@ -2822,6 +2824,14 @@ static int mlx5_vdpa_set_driver_features(struct vdpa_device *vdev, u64 features)
>                 }
>         }
>
> +       /* When below features diverge from initial device features, VQs need a full teardown. */
> +#define NEEDS_TEARDOWN_MASK (BIT_ULL(VIRTIO_NET_F_MRG_RXBUF) | \
> +                            BIT_ULL(VIRTIO_NET_F_CSUM) | \
> +                            BIT_ULL(VIRTIO_F_VERSION_1))
> +
> +       diff_features = mvdev->mlx_features ^ mvdev->actual_features;
> +       ndev->needs_teardown = !!(diff_features & NEEDS_TEARDOWN_MASK);
> +
>         update_cvq_info(mvdev);
>         return err;
>  }
> @@ -3038,6 +3048,7 @@ static void teardown_vq_resources(struct mlx5_vdpa_net *ndev)
>         destroy_rqt(ndev);
>         teardown_virtqueues(ndev);
>         ndev->setup = false;
> +       ndev->needs_teardown = false;
>  }
>
>  static int setup_cvq_vring(struct mlx5_vdpa_dev *mvdev)
> @@ -3078,6 +3089,10 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>                                 goto err_setup;
>                         }
>                         register_link_notifier(ndev);
> +
> +                       if (ndev->needs_teardown)
> +                               teardown_vq_resources(ndev);
> +
>                         if (ndev->setup) {
>                                 err = resume_vqs(ndev);
>                                 if (err) {
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.h b/drivers/vdpa/mlx5/net/mlx5_vnet.h
> index 2ada29767cc5..da7318f82d2a 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.h
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.h
> @@ -56,6 +56,7 @@ struct mlx5_vdpa_net {
>         struct dentry *rx_dent;
>         struct dentry *rx_table_dent;
>         bool setup;
> +       bool needs_teardown;
>         u32 cur_num_vqs;
>         u32 rqt_size;
>         u16 default_queue_size;
>
> --
> 2.45.1
>