Re: [PATCH vhost v4 12/16] vdpa/mlx5: Improve mr update flow

[Dragos Tatulea via Virtualization <virtualization@lists.linux-foundation.org>]

On Wed, 2023-10-18 at 20:14 +0300, Dragos Tatulea wrote:
> The current flow for updating an mr works directly on mvdev->mr which
> makes it cumbersome to handle multiple new mr structs.
> 
> This patch makes the flow more straightforward by having
> mlx5_vdpa_create_mr return a new mr which will update the old mr (if
> any). The old mr will be deleted and unlinked from mvdev. For the case
> when the iotlb is empty (not NULL), the old mr will be cleared.
> 
> This change paves the way for adding mrs for different ASIDs.
> 
> The initialized bool is no longer needed as mr is now a pointer in the
> mlx5_vdpa_dev struct which will be NULL when not initialized.
> 
> Acked-by: Eugenio Pérez <eperezma@redhat.com>
> Acked-by: Jason Wang <jasowang@redhat.com>
> Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
> ---
>  drivers/vdpa/mlx5/core/mlx5_vdpa.h | 14 +++--
>  drivers/vdpa/mlx5/core/mr.c        | 87 ++++++++++++++++--------------
>  drivers/vdpa/mlx5/net/mlx5_vnet.c  | 53 +++++++++---------
>  3 files changed, 82 insertions(+), 72 deletions(-)
> 
> diff --git a/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> index 9c6ac42c21e1..bbe4335106bd 100644
> --- a/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> +++ b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> @@ -31,8 +31,6 @@ struct mlx5_vdpa_mr {
>         struct list_head head;
>         unsigned long num_directs;
>         unsigned long num_klms;
> -       /* state of dvq mr */
> -       bool initialized;
>  
>         bool user_mr;
>  };
> @@ -91,7 +89,7 @@ struct mlx5_vdpa_dev {
>         u16 max_idx;
>         u32 generation;
>  
> -       struct mlx5_vdpa_mr mr;
> +       struct mlx5_vdpa_mr *mr;
>         /* serialize mr access */
>         struct mutex mr_mtx;
>         struct mlx5_control_vq cvq;
> @@ -114,14 +112,14 @@ void mlx5_vdpa_free_resources(struct mlx5_vdpa_dev
> *mvdev);
>  int mlx5_vdpa_create_mkey(struct mlx5_vdpa_dev *mvdev, u32 *mkey, u32 *in,
>                           int inlen);
>  int mlx5_vdpa_destroy_mkey(struct mlx5_vdpa_dev *mvdev, u32 mkey);
> -int mlx5_vdpa_handle_set_map(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb
> *iotlb,
> -                            bool *change_map, unsigned int asid);
> -int mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev,
> -                       struct mlx5_vdpa_mr *mr,
> -                       struct vhost_iotlb *iotlb);
> +struct mlx5_vdpa_mr *mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev,
> +                                        struct vhost_iotlb *iotlb);
>  void mlx5_vdpa_destroy_mr_resources(struct mlx5_vdpa_dev *mvdev);
>  void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev,
>                           struct mlx5_vdpa_mr *mr);
> +void mlx5_vdpa_update_mr(struct mlx5_vdpa_dev *mvdev,
> +                        struct mlx5_vdpa_mr *mr,
> +                        unsigned int asid);
>  int mlx5_vdpa_update_cvq_iotlb(struct mlx5_vdpa_dev *mvdev,
>                                 struct vhost_iotlb *iotlb,
>                                 unsigned int asid);
> diff --git a/drivers/vdpa/mlx5/core/mr.c b/drivers/vdpa/mlx5/core/mr.c
> index abd6a6fb122f..00eff5a07152 100644
> --- a/drivers/vdpa/mlx5/core/mr.c
> +++ b/drivers/vdpa/mlx5/core/mr.c
> @@ -495,30 +495,51 @@ static void destroy_user_mr(struct mlx5_vdpa_dev *mvdev,
> struct mlx5_vdpa_mr *mr
>  
>  static void _mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev, struct
> mlx5_vdpa_mr *mr)
>  {
> -       if (!mr->initialized)
> -               return;
> -
>         if (mr->user_mr)
>                 destroy_user_mr(mvdev, mr);
>         else
>                 destroy_dma_mr(mvdev, mr);
> -
> -       mr->initialized = false;
>  }
>  
>  void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev,
>                           struct mlx5_vdpa_mr *mr)
>  {
> +       if (!mr)
> +               return;
> +
>         mutex_lock(&mvdev->mr_mtx);
>  
>         _mlx5_vdpa_destroy_mr(mvdev, mr);
>  
> +       if (mvdev->mr == mr)
> +               mvdev->mr = NULL;
> +
> +       mutex_unlock(&mvdev->mr_mtx);
> +
> +       kfree(mr);
> +}
> +
> +void mlx5_vdpa_update_mr(struct mlx5_vdpa_dev *mvdev,
> +                        struct mlx5_vdpa_mr *new_mr,
> +                        unsigned int asid)
> +{
> +       struct mlx5_vdpa_mr *old_mr = mvdev->mr;
> +
> +       mutex_lock(&mvdev->mr_mtx);
> +
> +       mvdev->mr = new_mr;
> +       if (old_mr) {
> +               _mlx5_vdpa_destroy_mr(mvdev, old_mr);
> +               kfree(old_mr);
> +       }
> +
>         mutex_unlock(&mvdev->mr_mtx);
> +
>  }
>  
>  void mlx5_vdpa_destroy_mr_resources(struct mlx5_vdpa_dev *mvdev)
>  {
> -       mlx5_vdpa_destroy_mr(mvdev, &mvdev->mr);
> +       mlx5_vdpa_destroy_mr(mvdev, mvdev->mr);
>         prune_iotlb(mvdev);
>  }
>  
> @@ -528,52 +549,36 @@ static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev
> *mvdev,
>  {
>         int err;
>  
> -       if (mr->initialized)
> -               return 0;
> -
>         if (iotlb)
>                 err = create_user_mr(mvdev, mr, iotlb);
>         else
>                 err = create_dma_mr(mvdev, mr);
>  
> -       if (err)
> -               return err;
> -
> -       mr->initialized = true;
> -
> -       return 0;
> +       return err;
>  }
>  
> -int mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev,
> -                       struct mlx5_vdpa_mr *mr,
> -                       struct vhost_iotlb *iotlb)
> +struct mlx5_vdpa_mr *mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev,
> +                                        struct vhost_iotlb *iotlb)
>  {
> +       struct mlx5_vdpa_mr *mr;
>         int err;
>  
> +       mr = kzalloc(sizeof(*mr), GFP_KERNEL);
> +       if (!mr)
> +               return ERR_PTR(-ENOMEM);
> +
>         mutex_lock(&mvdev->mr_mtx);
>         err = _mlx5_vdpa_create_mr(mvdev, mr, iotlb);
>         mutex_unlock(&mvdev->mr_mtx);
>  
> -       return err;
> -}
> -
> -int mlx5_vdpa_handle_set_map(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb
> *iotlb,
> -                            bool *change_map, unsigned int asid)
> -{
> -       struct mlx5_vdpa_mr *mr = &mvdev->mr;
> -       int err = 0;
> +       if (err)
> +               goto out_err;
>  
> -       *change_map = false;
> -       mutex_lock(&mvdev->mr_mtx);
> -       if (mr->initialized) {
> -               mlx5_vdpa_info(mvdev, "memory map update\n");
> -               *change_map = true;
> -       }
> -       if (!*change_map)
> -               err = _mlx5_vdpa_create_mr(mvdev, mr, iotlb);
> -       mutex_unlock(&mvdev->mr_mtx);
> +       return mr;
>  
> -       return err;
> +out_err:
> +       kfree(mr);
> +       return ERR_PTR(err);
>  }
>  
>  int mlx5_vdpa_update_cvq_iotlb(struct mlx5_vdpa_dev *mvdev,
> @@ -597,11 +602,13 @@ int mlx5_vdpa_update_cvq_iotlb(struct mlx5_vdpa_dev
> *mvdev,
>  
>  int mlx5_vdpa_create_dma_mr(struct mlx5_vdpa_dev *mvdev)
>  {
> -       int err;
> +       struct mlx5_vdpa_mr *mr;
>  
> -       err = mlx5_vdpa_create_mr(mvdev, &mvdev->mr, NULL);
> -       if (err)
> -               return err;
> +       mr = mlx5_vdpa_create_mr(mvdev, NULL);
> +       if (IS_ERR(mr))
> +               return PTR_ERR(mr);
> +
> +       mlx5_vdpa_update_mr(mvdev, mr, 0);
>  
>         return mlx5_vdpa_update_cvq_iotlb(mvdev, NULL, 0);
>  }
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 256fdd80c321..7b878995b6aa 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -873,7 +873,7 @@ static int create_virtqueue(struct mlx5_vdpa_net *ndev,
> struct mlx5_vdpa_virtque
>         MLX5_SET64(virtio_q, vq_ctx, desc_addr, mvq->desc_addr);
>         MLX5_SET64(virtio_q, vq_ctx, used_addr, mvq->device_addr);
>         MLX5_SET64(virtio_q, vq_ctx, available_addr, mvq->driver_addr);
> -       MLX5_SET(virtio_q, vq_ctx, virtio_q_mkey, ndev->mvdev.mr.mkey);
> +       MLX5_SET(virtio_q, vq_ctx, virtio_q_mkey, ndev->mvdev.mr->mkey);
>         MLX5_SET(virtio_q, vq_ctx, umem_1_id, mvq->umem1.id);
>         MLX5_SET(virtio_q, vq_ctx, umem_1_size, mvq->umem1.size);
>         MLX5_SET(virtio_q, vq_ctx, umem_2_id, mvq->umem2.id);
> @@ -2633,7 +2633,7 @@ static void restore_channels_info(struct mlx5_vdpa_net
> *ndev)
>  }
>  
>  static int mlx5_vdpa_change_map(struct mlx5_vdpa_dev *mvdev,
> -                               struct vhost_iotlb *iotlb, unsigned int asid)
> +                               struct mlx5_vdpa_mr *new_mr, unsigned int
> asid)
>  {
>         struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
>         int err;
> @@ -2641,27 +2641,18 @@ static int mlx5_vdpa_change_map(struct mlx5_vdpa_dev
> *mvdev,
>         suspend_vqs(ndev);
>         err = save_channels_info(ndev);
>         if (err)
> -               goto err_mr;
> +               return err;
>  
>         teardown_driver(ndev);
> -       mlx5_vdpa_destroy_mr(mvdev, &mvdev->mr);
> -       err = mlx5_vdpa_create_mr(mvdev, &mvdev->mr, iotlb);
> -       if (err)
> -               goto err_mr;
> +
> +       mlx5_vdpa_update_mr(mvdev, new_mr, asid);
>  
>         if (!(mvdev->status & VIRTIO_CONFIG_S_DRIVER_OK) || mvdev->suspended)
> -               goto err_mr;
> +               return 0;
>  
>         restore_channels_info(ndev);
>         err = setup_driver(mvdev);
> -       if (err)
> -               goto err_setup;
> -
> -       return 0;
>  
> -err_setup:
> -       mlx5_vdpa_destroy_mr(mvdev, &mvdev->mr);
> -err_mr:
>         return err;
>  }
>  
> @@ -2875,26 +2866,40 @@ static u32 mlx5_vdpa_get_generation(struct vdpa_device
> *vdev)
>  static int set_map_data(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb
> *iotlb,
>                         unsigned int asid)
>  {
> -       bool change_map;
> +       struct mlx5_vdpa_mr *new_mr;
>         int err;
>  
>         if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] != asid)
>                 goto end;
>  
> -       err = mlx5_vdpa_handle_set_map(mvdev, iotlb, &change_map, asid);
> -       if (err) {
> -               mlx5_vdpa_warn(mvdev, "set map failed(%d)\n", err);
> -               return err;
> +       if (vhost_iotlb_itree_first(iotlb, 0, U64_MAX)) {
> +               new_mr = mlx5_vdpa_create_mr(mvdev, iotlb);
> +               if (IS_ERR(new_mr)) {
> +                       err = PTR_ERR(new_mr);
> +                       mlx5_vdpa_warn(mvdev, "create map failed(%d)\n", err);
> +                       return err;
> +               }
> +       } else {
> +               /* Empty iotlbs don't have an mr but will clear the previous
> mr. */
> +               new_mr = NULL;
>         }
Hi Jason and/or Eugenio, could you have a quick look at this part of the patch
that changed please?

Thanks,
Dragos
>  
> -       if (change_map) {
> -               err = mlx5_vdpa_change_map(mvdev, iotlb, asid);
> -               if (err)
> -                       return err;
> +       if (!mvdev->mr) {
> +               mlx5_vdpa_update_mr(mvdev, new_mr, asid);
> +       } else {
> +               err = mlx5_vdpa_change_map(mvdev, new_mr, asid);
> +               if (err) {
> +                       mlx5_vdpa_warn(mvdev, "change map failed(%d)\n", err);
> +                       goto out_err;
> +               }
>         }
>  
>  end:
>         return mlx5_vdpa_update_cvq_iotlb(mvdev, iotlb, asid);
> +
> +out_err:
> +       mlx5_vdpa_destroy_mr(mvdev, new_mr);
> +       return err;
>  }
>  
>  static int mlx5_vdpa_set_map(struct vdpa_device *vdev, unsigned int asid,

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