Re: [PATCH vhost 14/16] vdpa/mlx5: Enable hw support for vq descriptor mapping

From: Eugenio Perez Martin
Date: Thu Oct 05 2023 - 12:41:38 EST

On Thu, Sep 28, 2023 at 6:50 PM Dragos Tatulea <dtatulea@xxxxxxxxxx> wrote:
>
> Vq descriptor mappings are supported in hardware by filling in an
> additional mkey which contains the descriptor mappings to the hw vq.
>
> A previous patch in this series added support for hw mkey (mr) creation
> for ASID 1.
>
> This patch fills in both the vq data and vq descriptor mkeys based on
> group ASID mapping.
>
> The feature is signaled to the vdpa core through the presence of the
> .get_vq_desc_group op.
>
> Signed-off-by: Dragos Tatulea <dtatulea@xxxxxxxxxx>
> ---
> drivers/vdpa/mlx5/net/mlx5_vnet.c | 26 ++++++++++++++++++++++++--
> include/linux/mlx5/mlx5_ifc_vdpa.h | 7 ++++++-
> 2 files changed, 30 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 25bd2c324f5b..46441e41892c 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -823,6 +823,7 @@ static int create_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtque
> u32 out[MLX5_ST_SZ_DW(create_virtio_net_q_out)] = {};
> struct mlx5_vdpa_dev *mvdev = &ndev->mvdev;
> struct mlx5_vdpa_mr *vq_mr;
> + struct mlx5_vdpa_mr *vq_desc_mr;
> void *obj_context;
> u16 mlx_features;
> void *cmd_hdr;
> @@ -878,6 +879,11 @@ static int create_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtque
> vq_mr = mvdev->mr[mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP]];
> if (vq_mr)
> MLX5_SET(virtio_q, vq_ctx, virtio_q_mkey, vq_mr->mkey);
> +
> + vq_desc_mr = mvdev->mr[mvdev->group2asid[MLX5_VDPA_DATAVQ_DESC_GROUP]];
> + if (vq_desc_mr)
> + MLX5_SET(virtio_q, vq_ctx, desc_group_mkey, vq_desc_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);
> @@ -2265,6 +2271,16 @@ static u32 mlx5_vdpa_get_vq_group(struct vdpa_device *vdev, u16 idx)
> return MLX5_VDPA_DATAVQ_GROUP;
> }
>
> +static u32 mlx5_vdpa_get_vq_desc_group(struct vdpa_device *vdev, u16 idx)
> +{
> + struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> +
> + if (is_ctrl_vq_idx(mvdev, idx))
> + return MLX5_VDPA_CVQ_GROUP;
> +
> + return MLX5_VDPA_DATAVQ_DESC_GROUP;
> +}
> +
> static u64 mlx_to_vritio_features(u16 dev_features)
> {
> u64 result = 0;
> @@ -3139,7 +3155,7 @@ static int mlx5_set_group_asid(struct vdpa_device *vdev, u32 group,
> {
> struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
>
> - if (group >= MLX5_VDPA_NUMVQ_GROUPS)
> + if (group >= MLX5_VDPA_NUMVQ_GROUPS || asid >= MLX5_VDPA_NUM_AS)

Nit: the check for asid >= MLX5_VDPA_NUM_AS is redundant, as it will
be already checked by VHOST_VDPA_SET_GROUP_ASID handler in
drivers/vhost/vdpa.c:vhost_vdpa_vring_ioctl. Not a big deal.

> return -EINVAL;
>
> mvdev->group2asid[group] = asid;
> @@ -3160,6 +3176,7 @@ static const struct vdpa_config_ops mlx5_vdpa_ops = {
> .get_vq_irq = mlx5_get_vq_irq,
> .get_vq_align = mlx5_vdpa_get_vq_align,
> .get_vq_group = mlx5_vdpa_get_vq_group,
> + .get_vq_desc_group = mlx5_vdpa_get_vq_desc_group, /* Op disabled if not supported. */
> .get_device_features = mlx5_vdpa_get_device_features,
> .set_driver_features = mlx5_vdpa_set_driver_features,
> .get_driver_features = mlx5_vdpa_get_driver_features,
> @@ -3258,6 +3275,7 @@ struct mlx5_vdpa_mgmtdev {
> struct vdpa_mgmt_dev mgtdev;
> struct mlx5_adev *madev;
> struct mlx5_vdpa_net *ndev;
> + struct vdpa_config_ops vdpa_ops;
> };
>
> static int config_func_mtu(struct mlx5_core_dev *mdev, u16 mtu)
> @@ -3371,7 +3389,7 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
> max_vqs = 2;
> }
>
> - ndev = vdpa_alloc_device(struct mlx5_vdpa_net, mvdev.vdev, mdev->device, &mlx5_vdpa_ops,
> + ndev = vdpa_alloc_device(struct mlx5_vdpa_net, mvdev.vdev, mdev->device, &mgtdev->vdpa_ops,
> MLX5_VDPA_NUMVQ_GROUPS, MLX5_VDPA_NUM_AS, name, false);
> if (IS_ERR(ndev))
> return PTR_ERR(ndev);
> @@ -3546,6 +3564,10 @@ static int mlx5v_probe(struct auxiliary_device *adev,
> MLX5_CAP_DEV_VDPA_EMULATION(mdev, max_num_virtio_queues) + 1;
> mgtdev->mgtdev.supported_features = get_supported_features(mdev);
> mgtdev->madev = madev;
> + mgtdev->vdpa_ops = mlx5_vdpa_ops;
> +
> + if (!MLX5_CAP_DEV_VDPA_EMULATION(mdev, desc_group_mkey_supported))
> + mgtdev->vdpa_ops.get_vq_desc_group = NULL;

I think this is better handled by splitting mlx5_vdpa_ops in two: One
with get_vq_desc_group and other without it. You can see an example of
this in the simulator, where one version supports .dma_map incremental
updating with .dma_map and the other supports .set_map. Otherwise,
this can get messy if more members opt-out or opt-in.

But I'm ok with this too, so whatever version you choose:

Acked-by: Eugenio Pérez <eperezma@xxxxxxxxxx>

>
> err = vdpa_mgmtdev_register(&mgtdev->mgtdev);
> if (err)
> diff --git a/include/linux/mlx5/mlx5_ifc_vdpa.h b/include/linux/mlx5/mlx5_ifc_vdpa.h
> index 9becdc3fa503..b86d51a855f6 100644
> --- a/include/linux/mlx5/mlx5_ifc_vdpa.h
> +++ b/include/linux/mlx5/mlx5_ifc_vdpa.h
> @@ -74,7 +74,11 @@ struct mlx5_ifc_virtio_q_bits {
> u8 reserved_at_320[0x8];
> u8 pd[0x18];
>
> - u8 reserved_at_340[0xc0];
> + u8 reserved_at_340[0x20];
> +
> + u8 desc_group_mkey[0x20];
> +
> + u8 reserved_at_380[0x80];
> };
>
> struct mlx5_ifc_virtio_net_q_object_bits {
> @@ -141,6 +145,7 @@ enum {
> MLX5_VIRTQ_MODIFY_MASK_STATE = (u64)1 << 0,
> MLX5_VIRTQ_MODIFY_MASK_DIRTY_BITMAP_PARAMS = (u64)1 << 3,
> MLX5_VIRTQ_MODIFY_MASK_DIRTY_BITMAP_DUMP_ENABLE = (u64)1 << 4,
> + MLX5_VIRTQ_MODIFY_MASK_DESC_GROUP_MKEY = (u64)1 << 14,
> };
>
> enum {
> --
> 2.41.0
>