Re: [PATCH RFC 1/3] vdpa/mlx5: Implement susupend virtqueue callback

Jason Wang
2022-06-20T08:56:38Z

On Thu, Jun 16, 2022 at 9:27 PM Eli Cohen <elic@nvidia.com> wrote:
>
> Implement the suspend callback allowing to suspend the virtqueues so
> they stop processing descriptors. This is required to allow the shadow
> virtqueue to kick in.
>
> Signed-off-by: Eli Cohen <elic@nvidia.com>
> ---
> drivers/vdpa/mlx5/net/mlx5_vnet.c | 68 +++++++++++++++++++++++++++++-
> include/linux/mlx5/mlx5_ifc_vdpa.h | 8 ++++
> 2 files changed, 75 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index fb0b23e71383..ea4bc8a0cd25 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -895,6 +895,7 @@ static int create_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtque
> if (err)
> goto err_cmd;
>
> + mvq->fw_state = MLX5_VIRTIO_NET_Q_OBJECT_STATE_INIT;
> kfree(in);
> mvq->virtq_id = MLX5_GET(general_obj_out_cmd_hdr, out, obj_id);
>
> @@ -922,6 +923,7 @@ static void destroy_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtq
> mlx5_vdpa_warn(&ndev->mvdev, "destroy virtqueue 0x%x\n", mvq->virtq_id);
> return;
> }
> + mvq->fw_state = MLX5_VIRTIO_NET_Q_OBJECT_NONE;
> umems_destroy(ndev, mvq);
> }
>
> @@ -1121,6 +1123,20 @@ static int query_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueu
> return err;
> }
>
> +static bool is_valid_state_change(int oldstate, int newstate)
> +{
> + switch (oldstate) {
> + case MLX5_VIRTIO_NET_Q_OBJECT_STATE_INIT:
> + return newstate == MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY;
> + case MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY:
> + return newstate == MLX5_VIRTIO_NET_Q_OBJECT_STATE_SUSPEND;
> + case MLX5_VIRTIO_NET_Q_OBJECT_STATE_SUSPEND:
> + case MLX5_VIRTIO_NET_Q_OBJECT_STATE_ERR:
> + default:
> + return false;
> + }
> +}
> +
> static int modify_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq, int state)
> {
> int inlen = MLX5_ST_SZ_BYTES(modify_virtio_net_q_in);
> @@ -1130,6 +1146,12 @@ static int modify_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtque
> void *in;
> int err;
>
> + if (mvq->fw_state == MLX5_VIRTIO_NET_Q_OBJECT_NONE)
> + return 0;
> +
> + if (!is_valid_state_change(mvq->fw_state, state))
> + return -EINVAL;
> +
> in = kzalloc(inlen, GFP_KERNEL);
> if (!in)
> return -ENOMEM;
> @@ -1991,6 +2013,7 @@ static void mlx5_vdpa_set_vq_ready(struct vdpa_device *vdev, u16 idx, bool ready
> struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
> struct mlx5_vdpa_virtqueue *mvq;
> + int err;
>
> if (!mvdev->actual_features)
> return;
> @@ -2004,8 +2027,16 @@ static void mlx5_vdpa_set_vq_ready(struct vdpa_device *vdev, u16 idx, bool ready
> }
>
> mvq = &ndev->vqs[idx];
> - if (!ready)
> + if (!ready) {
> suspend_vq(ndev, mvq);
> + } else {
> + err = modify_virtqueue(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY);
> + if (err) {
> + mlx5_vdpa_warn(mvdev, "modify VQ %d to ready failed (%d)\n", idx, err);
> + ready = false;
> + }
> + }
> +
>
> mvq->ready = ready;
> }
> @@ -2732,6 +2763,39 @@ static int mlx5_vdpa_get_vendor_vq_stats(struct vdpa_device *vdev, u16 idx,
> return err;
> }
>
> +static void mlx5_vdpa_cvq_suspend(struct mlx5_vdpa_dev *mvdev, bool suspend)
> +{
> + struct mlx5_control_vq *cvq;
> +
> + if (!(mvdev->actual_features & BIT_ULL(VIRTIO_NET_F_CTRL_VQ)))
> + return;
> +
> + cvq = &mvdev->cvq;
> + cvq->ready = !suspend;
> +}

It looks to me we need to synchronize this with reslock. And this
probably deserve a dedicated fix.

> +
> +static int mlx5_vdpa_suspend(struct vdpa_device *vdev, bool suspend)
> +{
> + struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> + struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
> + struct mlx5_vdpa_virtqueue *mvq;
> + int i;
> +
> + if (!suspend) {
> + mlx5_vdpa_warn(mvdev, "Resume of virtqueues is not supported\n");
> + return -EOPNOTSUPP;
> + }
> +
> + down_write(&ndev->reslock);
> + for (i = 0; i < ndev->cur_num_vqs; i++) {
> + mvq = &ndev->vqs[i];
> + suspend_vq(ndev, mvq);
> + }
> + mlx5_vdpa_cvq_suspend(mvdev, suspend);

Do we need to synchronize with the carrier work here? Otherwise we may
get config notification after suspending.

> + up_write(&ndev->reslock);
> + return 0;
> +}
> +
> static const struct vdpa_config_ops mlx5_vdpa_ops = {
> .set_vq_address = mlx5_vdpa_set_vq_address,
> .set_vq_num = mlx5_vdpa_set_vq_num,
> @@ -2762,6 +2826,7 @@ static const struct vdpa_config_ops mlx5_vdpa_ops = {
> .get_generation = mlx5_vdpa_get_generation,
> .set_map = mlx5_vdpa_set_map,
> .free = mlx5_vdpa_free,
> + .suspend = mlx5_vdpa_suspend,

I don't see the vDPA bus patch to enable this method. Or anything I missed here?

Thanks

> };
>
> static int query_mtu(struct mlx5_core_dev *mdev, u16 *mtu)
> @@ -2827,6 +2892,7 @@ static void init_mvqs(struct mlx5_vdpa_net *ndev)
> mvq->index = i;
> mvq->ndev = ndev;
> mvq->fwqp.fw = true;
> + mvq->fw_state = MLX5_VIRTIO_NET_Q_OBJECT_NONE;
> }
> for (; i < ndev->mvdev.max_vqs; i++) {
> mvq = &ndev->vqs[i];
> diff --git a/include/linux/mlx5/mlx5_ifc_vdpa.h b/include/linux/mlx5/mlx5_ifc_vdpa.h
> index 4414ed5b6ed2..423562f39d3c 100644
> --- a/include/linux/mlx5/mlx5_ifc_vdpa.h
> +++ b/include/linux/mlx5/mlx5_ifc_vdpa.h
> @@ -150,6 +150,14 @@ enum {
> MLX5_VIRTIO_NET_Q_OBJECT_STATE_ERR = 0x3,
> };
>
> +/* This indicates that the object was not created or has alreadyi
> + * been desroyed. It is very safe to assume that this object will never
> + * have so many states
> + */
> +enum {
> + MLX5_VIRTIO_NET_Q_OBJECT_NONE = 0xffffffff
> +};
> +
> enum {
> MLX5_RQTC_LIST_Q_TYPE_RQ = 0x0,
> MLX5_RQTC_LIST_Q_TYPE_VIRTIO_NET_Q = 0x1,
> --
> 2.35.1
>