linux-kernel - Re: [PATCH vhost 16/16] vdpa/mlx5: Update cvq iotlb mapping on ASID change

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Message-ID: <CAJaqyWe9iYnh_DwZbU4986bSAZ0C1=Y9Th6-vv_ZRTTYwQqhYA@mail.gmail.com>
Date:   Thu, 5 Oct 2023 12:41:48 +0200
From:   Eugenio Perez Martin <eperezma@...hat.com>
To:     Dragos Tatulea <dtatulea@...dia.com>
Cc:     gal@...dia.com, "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH vhost 16/16] vdpa/mlx5: Update cvq iotlb mapping on ASID change

On Thu, Sep 28, 2023 at 6:50 PM Dragos Tatulea <dtatulea@...dia.com> wrote:
>
> For the following sequence:
> - cvq group is in ASID 0
> - .set_map(1, cvq_iotlb)
> - .set_group_asid(cvq_group, 1)
>
> ... the cvq mapping from ASID 0 will be used. This is not always correct
> behaviour.
>
> This patch adds support for the above mentioned flow by saving the iotlb
> on each .set_map and updating the cvq iotlb with it on a cvq group change.
>
> Signed-off-by: Dragos Tatulea <dtatulea@...dia.com>
> ---
>  drivers/vdpa/mlx5/core/mlx5_vdpa.h |  2 ++
>  drivers/vdpa/mlx5/core/mr.c        | 26 ++++++++++++++++++++++++++
>  drivers/vdpa/mlx5/net/mlx5_vnet.c  |  9 ++++++++-
>  3 files changed, 36 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vdpa/mlx5/core/mlx5_vdpa.h b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> index ae09296f4270..db988ced5a5d 100644
> --- a/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> +++ b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> @@ -32,6 +32,8 @@ struct mlx5_vdpa_mr {
>         unsigned long num_directs;
>         unsigned long num_klms;
>
> +       struct vhost_iotlb *iotlb;
> +
>         bool user_mr;
>  };
>
> diff --git a/drivers/vdpa/mlx5/core/mr.c b/drivers/vdpa/mlx5/core/mr.c
> index a4135c16b5bf..403c08271489 100644
> --- a/drivers/vdpa/mlx5/core/mr.c
> +++ b/drivers/vdpa/mlx5/core/mr.c
> @@ -499,6 +499,8 @@ static void _mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev, struct mlx5_vdpa_
>                 destroy_user_mr(mvdev, mr);
>         else
>                 destroy_dma_mr(mvdev, mr);
> +
> +       vhost_iotlb_free(mr->iotlb);
>  }
>
>  void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev,
> @@ -558,6 +560,30 @@ static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev,
>         else
>                 err = create_dma_mr(mvdev, mr);
>
> +       if (err)
> +               return err;
> +
> +       mr->iotlb = vhost_iotlb_alloc(0, 0);
> +       if (!mr->iotlb) {
> +               err = -ENOMEM;
> +               goto err_mr;
> +       }
> +
> +       err = dup_iotlb(mr->iotlb, iotlb);
> +       if (err)
> +               goto err_iotlb;
> +
> +       return 0;
> +
> +err_iotlb:
> +       vhost_iotlb_free(mr->iotlb);
> +
> +err_mr:
> +       if (iotlb)
> +               destroy_user_mr(mvdev, mr);
> +       else
> +               destroy_dma_mr(mvdev, mr);
> +
>         return err;
>  }
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 46441e41892c..fc5d6b989a5a 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -3154,12 +3154,19 @@ static int mlx5_set_group_asid(struct vdpa_device *vdev, u32 group,
>                                unsigned int asid)
>  {
>         struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> +       int err = 0;
>
>         if (group >= MLX5_VDPA_NUMVQ_GROUPS || asid >= MLX5_VDPA_NUM_AS)
>                 return -EINVAL;
>
>         mvdev->group2asid[group] = asid;
> -       return 0;
> +
> +       mutex_lock(&mvdev->mr_mtx);
> +       if (group == MLX5_VDPA_CVQ_GROUP && mvdev->mr[asid])
> +               err = mlx5_vdpa_update_cvq_iotlb(mvdev, mvdev->mr[asid]->iotlb, asid);

Do we need to protect here in case userspace sets the same ASID twice?
mlx5_vdpa_update_cvq_iotlb shouldn't call dup_iotlb with the same src
and dst.

Apart from that:

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

> +       mutex_unlock(&mvdev->mr_mtx);
> +
> +       return err;
>  }
>
>  static const struct vdpa_config_ops mlx5_vdpa_ops = {
> --
> 2.41.0
>