On Sat, Sep 9, 2023 at 9:46 PM Si-Wei Liu <si-wei.liu@xxxxxxxxxx> 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@xxxxxxxxxx>
>
> ---
> 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
>
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