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

[Eli Cohen]

> -----Original Message-----
> From: Jason Wang <jasowang@xxxxxxxxxx>
> Sent: Monday, June 20, 2022 11:56 AM
> To: Eli Cohen <elic@xxxxxxxxxx>
> Cc: eperezma <eperezma@xxxxxxxxxx>; mst <mst@xxxxxxxxxx>; virtualization <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx>; linux-
> kernel <linux-kernel@xxxxxxxxxxxxxxx>; Si-Wei Liu <si-wei.liu@xxxxxxxxxx>; Parav Pandit <parav@xxxxxxxxxx>
> Subject: Re: [PATCH RFC 1/3] vdpa/mlx5: Implement susupend virtqueue callback
> 
> On Thu, Jun 16, 2022 at 9:27 PM Eli Cohen <elic@xxxxxxxxxx> 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@xxxxxxxxxx>
> > ---
> >  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.
> 

It's already being held by mlx5_vdpa_suspend

> > +
> > +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.
> 

Are you saying we should not allow carrier updates after the VQs have been suspended?
Link state should not be related to suspension of VQs.

> > +       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
> >