Re: [PATCH vhost 22/23] vdpa/mlx5: Don't reset VQs more than necessary

Eugenio Perez Martin
2024-06-19T16:15:24Z

On Mon, Jun 17, 2024 at 5:09 PM Dragos Tatulea <dtatulea@nvidia.com> wrote:
>
> The vdpa device can be reset many times in sequence without any
> significant state changes in between. Previously this was not a problem:
> VQs were torn down only on first reset. But after VQ pre-creation was
> introduced, each reset will delete and re-create the hardware VQs and
> their associated resources.
>
> To solve this problem, avoid resetting hardware VQs if the VQs are still
> in a blank state.
>
> Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
> Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>

Acked-by: Eugenio Pérez <eperezma@redhat.com>

> ---
> drivers/vdpa/mlx5/net/mlx5_vnet.c | 30 +++++++++++++++++++++++++++---
> 1 file changed, 27 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index d80d6b47da61..1a5ee0d2b47f 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -3134,18 +3134,41 @@ static void init_group_to_asid_map(struct mlx5_vdpa_dev *mvdev)
> mvdev->group2asid[i] = 0;
> }
>
> +static bool needs_vqs_reset(const struct mlx5_vdpa_dev *mvdev)
> +{
> + struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
> + struct mlx5_vdpa_virtqueue *mvq = &ndev->vqs[0];
> +
> + if (mvdev->status & VIRTIO_CONFIG_S_DRIVER_OK)
> + return true;
> +
> + if (mvq->fw_state != MLX5_VIRTIO_NET_Q_OBJECT_STATE_INIT)
> + return true;
> +
> + return mvq->modified_fields & (
> + MLX5_VIRTQ_MODIFY_MASK_STATE |
> + MLX5_VIRTQ_MODIFY_MASK_VIRTIO_Q_ADDRS |
> + MLX5_VIRTQ_MODIFY_MASK_VIRTIO_Q_AVAIL_IDX |
> + MLX5_VIRTQ_MODIFY_MASK_VIRTIO_Q_USED_IDX
> + );
> +}
> +
> static int mlx5_vdpa_compat_reset(struct vdpa_device *vdev, u32 flags)
> {
> struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
> + bool vq_reset;
>
> print_status(mvdev, 0, true);
> mlx5_vdpa_info(mvdev, "performing device reset\n");
>
> down_write(&ndev->reslock);
> unregister_link_notifier(ndev);
> - teardown_vq_resources(ndev);
> - init_mvqs(ndev);
> + vq_reset = needs_vqs_reset(mvdev);
> + if (vq_reset) {
> + teardown_vq_resources(ndev);
> + init_mvqs(ndev);
> + }
>
> if (flags & VDPA_RESET_F_CLEAN_MAP)
> mlx5_vdpa_destroy_mr_resources(&ndev->mvdev);
> @@ -3165,7 +3188,8 @@ static int mlx5_vdpa_compat_reset(struct vdpa_device *vdev, u32 flags)
> if (mlx5_vdpa_create_dma_mr(mvdev))
> mlx5_vdpa_warn(mvdev, "create MR failed\n");
> }
> - setup_vq_resources(ndev, false);
> + if (vq_reset)
> + setup_vq_resources(ndev, false);
> up_write(&ndev->reslock);
>
> return 0;
>
> --
> 2.45.1
>