[PATCH RFC v3 2/4] vdpa/mlx5: implement .reset_map driver op

Jason Wang
Mon, 11 Sep 2023 03:48:19 -0000

On Sat, Sep 9, 2023 at 9:46?PM Si-Wei Liu <si-wei.liu at oracle.com>
wrote:
>
> Today, mlx5_vdpa gets started by preallocate 1:1 DMA mapping at
> device creation time, while this 1:1 mapping will be implicitly
> destroyed when the first .set_map call is invoked. Everytime
> when the .reset callback is invoked, any mapping left behind will
> be dropped then reset back to the initial 1:1 DMA mapping.
>
> In order to reduce excessive memory mapping cost during live
> migration, it is desirable to decouple the vhost-vdpa iotlb
> abstraction from the virtio device life cycle, i.e. mappings
> should be left intact across virtio device reset. Leverage the
> .reset_map callback to reset memory mapping, then the device
> .reset routine can run free from having to clean up memory
> mappings.

It's not clear the direct relationship between the persistent mapping
and reset_map. Could we do it step by step? For example, remove the
mlx5_vdpa_destroy_mr() in mlx5_vdpa_reset() when PERSIST_IOTLB exists?
And then we can deal with the resetting and others on top, or it needs
some explanation for why reset_map() must be done first.

Thanks

>
> Signed-off-by: Si-Wei Liu <si-wei.liu at oracle.com>
>
> ---
> RFC v1 -> v2:
>   - fix error path when both CVQ and DVQ fall in same asid
> ---
>  drivers/vdpa/mlx5/core/mlx5_vdpa.h |  1 +
>  drivers/vdpa/mlx5/core/mr.c        | 70
+++++++++++++++++++++++---------------
>  drivers/vdpa/mlx5/net/mlx5_vnet.c  | 18 +++++++---
>  3 files changed, 56 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/vdpa/mlx5/core/mlx5_vdpa.h
b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> index b53420e..5c9a25a 100644
> --- a/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> +++ b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> @@ -123,6 +123,7 @@ int mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev,
struct vhost_iotlb *iotlb,
>                         unsigned int asid);
>  void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev);
>  void mlx5_vdpa_destroy_mr_asid(struct mlx5_vdpa_dev *mvdev, unsigned int
asid);
> +int mlx5_vdpa_reset_mr(struct mlx5_vdpa_dev *mvdev, unsigned int asid);
>
>  #define mlx5_vdpa_warn(__dev, format, ...)
\
>         dev_warn((__dev)->mdev->device, "%s:%d:(pid %d) warning:
" format, __func__, __LINE__,     \
> diff --git a/drivers/vdpa/mlx5/core/mr.c b/drivers/vdpa/mlx5/core/mr.c
> index 5a1971fc..ec2c7b4e1 100644
> --- a/drivers/vdpa/mlx5/core/mr.c
> +++ b/drivers/vdpa/mlx5/core/mr.c
> @@ -489,21 +489,15 @@ static void destroy_user_mr(struct mlx5_vdpa_dev
*mvdev, struct mlx5_vdpa_mr *mr
>         }
>  }
>
> -static void _mlx5_vdpa_destroy_cvq_mr(struct mlx5_vdpa_dev *mvdev,
unsigned int asid)
> +static void _mlx5_vdpa_destroy_cvq_mr(struct mlx5_vdpa_dev *mvdev)
>  {
> -       if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] != asid)
> -               return;
> -
>         prune_iotlb(mvdev);
>  }
>
> -static void _mlx5_vdpa_destroy_dvq_mr(struct mlx5_vdpa_dev *mvdev,
unsigned int asid)
> +static void _mlx5_vdpa_destroy_dvq_mr(struct mlx5_vdpa_dev *mvdev)
>  {
>         struct mlx5_vdpa_mr *mr = &mvdev->mr;
>
> -       if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] != asid)
> -               return;
> -
>         if (!mr->initialized)
>                 return;
>
> @@ -521,8 +515,10 @@ void mlx5_vdpa_destroy_mr_asid(struct mlx5_vdpa_dev
*mvdev, unsigned int asid)
>
>         mutex_lock(&mr->mkey_mtx);
>
> -       _mlx5_vdpa_destroy_dvq_mr(mvdev, asid);
> -       _mlx5_vdpa_destroy_cvq_mr(mvdev, asid);
> +       if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid)
> +               _mlx5_vdpa_destroy_dvq_mr(mvdev);
> +       if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] == asid)
> +               _mlx5_vdpa_destroy_cvq_mr(mvdev);
>
>         mutex_unlock(&mr->mkey_mtx);
>  }
> @@ -534,25 +530,17 @@ void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev
*mvdev)
>  }
>
>  static int _mlx5_vdpa_create_cvq_mr(struct mlx5_vdpa_dev *mvdev,
> -                                   struct vhost_iotlb *iotlb,
> -                                   unsigned int asid)
> +                                   struct vhost_iotlb *iotlb)
>  {
> -       if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] != asid)
> -               return 0;
> -
>         return dup_iotlb(mvdev, iotlb);
>  }
>
>  static int _mlx5_vdpa_create_dvq_mr(struct mlx5_vdpa_dev *mvdev,
> -                                   struct vhost_iotlb *iotlb,
> -                                   unsigned int asid)
> +                                   struct vhost_iotlb *iotlb)
>  {
>         struct mlx5_vdpa_mr *mr = &mvdev->mr;
>         int err;
>
> -       if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] != asid)
> -               return 0;
> -
>         if (mr->initialized)
>                 return 0;
>
> @@ -574,18 +562,22 @@ static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev
*mvdev,
>  {
>         int err;
>
> -       err = _mlx5_vdpa_create_dvq_mr(mvdev, iotlb, asid);
> -       if (err)
> -               return err;
> -
> -       err = _mlx5_vdpa_create_cvq_mr(mvdev, iotlb, asid);
> -       if (err)
> -               goto out_err;
> +       if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid) {
> +               err = _mlx5_vdpa_create_dvq_mr(mvdev, iotlb);
> +               if (err)
> +                       return err;
> +       }
> +       if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] == asid) {
> +               err = _mlx5_vdpa_create_cvq_mr(mvdev, iotlb);
> +               if (err)
> +                       goto out_err;
> +       }
>
>         return 0;
>
>  out_err:
> -       _mlx5_vdpa_destroy_dvq_mr(mvdev, asid);
> +       if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid)
> +               _mlx5_vdpa_destroy_dvq_mr(mvdev);
>
>         return err;
>  }
> @@ -601,6 +593,28 @@ int mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev,
struct vhost_iotlb *iotlb,
>         return err;
>  }
>
> +int mlx5_vdpa_reset_mr(struct mlx5_vdpa_dev *mvdev, unsigned int asid)
> +{
> +       struct mlx5_vdpa_mr *mr = &mvdev->mr;
> +       int err = 0;
> +
> +       if (asid != 0)
> +               return 0;
> +
> +       mutex_lock(&mr->mkey_mtx);
> +       if (!mr->user_mr)
> +               goto out;
> +       _mlx5_vdpa_destroy_dvq_mr(mvdev);
> +       if (MLX5_CAP_GEN(mvdev->mdev, umem_uid_0)) {
> +               err = _mlx5_vdpa_create_dvq_mr(mvdev, NULL);
> +               if (err)
> +                       mlx5_vdpa_warn(mvdev, "create DMA MR
failed\n");
> +       }
> +out:
> +       mutex_unlock(&mr->mkey_mtx);
> +       return err;
> +}
> +
>  int mlx5_vdpa_handle_set_map(struct mlx5_vdpa_dev *mvdev, struct
vhost_iotlb *iotlb,
>                              bool *change_map, unsigned int asid)
>  {
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c
b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 37be945..3cb5db6 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -2824,7 +2824,6 @@ static int mlx5_vdpa_reset(struct vdpa_device *vdev)
>         unregister_link_notifier(ndev);
>         teardown_driver(ndev);
>         clear_vqs_ready(ndev);
> -       mlx5_vdpa_destroy_mr(&ndev->mvdev);
>         ndev->mvdev.status = 0;
>         ndev->mvdev.suspended = false;
>         ndev->cur_num_vqs = 0;
> @@ -2835,10 +2834,6 @@ static int mlx5_vdpa_reset(struct vdpa_device *vdev)
>         init_group_to_asid_map(mvdev);
>         ++mvdev->generation;
>
> -       if (MLX5_CAP_GEN(mvdev->mdev, umem_uid_0)) {
> -               if (mlx5_vdpa_create_mr(mvdev, NULL, 0))
> -                       mlx5_vdpa_warn(mvdev, "create MR
failed\n");
> -       }
>         up_write(&ndev->reslock);
>
>         return 0;
> @@ -2903,6 +2898,18 @@ static int mlx5_vdpa_set_map(struct vdpa_device
*vdev, unsigned int asid,
>         return err;
>  }
>
> +static int mlx5_vdpa_reset_map(struct vdpa_device *vdev, unsigned int
asid)
> +{
> +       struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> +       struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
> +       int err;
> +
> +       down_write(&ndev->reslock);
> +       err = mlx5_vdpa_reset_mr(mvdev, asid);
> +       up_write(&ndev->reslock);
> +       return err;
> +}
> +
>  static struct device *mlx5_get_vq_dma_dev(struct vdpa_device *vdev, u16
idx)
>  {
>         struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> @@ -3162,6 +3169,7 @@ static int mlx5_set_group_asid(struct vdpa_device
*vdev, u32 group,
>         .set_config = mlx5_vdpa_set_config,
>         .get_generation = mlx5_vdpa_get_generation,
>         .set_map = mlx5_vdpa_set_map,
> +       .reset_map = mlx5_vdpa_reset_map,
>         .set_group_asid = mlx5_set_group_asid,
>         .get_vq_dma_dev = mlx5_get_vq_dma_dev,
>         .free = mlx5_vdpa_free,
> --
> 1.8.3.1
>