Re: [PATCH 15/18] vhost-net: control virtqueue support

[Eugenio Perez Martin <eperezma@redhat.com>]

On Mon, Jun 21, 2021 at 6:18 AM Jason Wang <jasowang@redhat.com> wrote:
>
> We assume there's no cvq in the past, this is not true when we need
> control virtqueue support for vhost-user backends. So this patch
> implements the control virtqueue support for vhost-net. As datapath,
> the control virtqueue is also required to be coupled with the
> NetClientState. The vhost_net_start/stop() are tweaked to accept the
> number of datapath queue pairs plus the the number of control
> virtqueue for us to start and stop the vhost device.
>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  hw/net/vhost_net.c      | 43 ++++++++++++++++++++++++++++++-----------
>  hw/net/virtio-net.c     |  4 ++--
>  include/net/vhost_net.h |  6 ++++--
>  3 files changed, 38 insertions(+), 15 deletions(-)
>
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index ef1370bd92..fe2fd7e3d5 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -311,11 +311,14 @@ static void vhost_net_stop_one(struct vhost_net *net,
>  }
>
>  int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
> -                    int total_queues)
> +                    int data_qps, int cvq)

I can see the convenience of being an int, but maybe it is more clear
to use a boolean?

>  {
>      BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(dev)));
>      VirtioBusState *vbus = VIRTIO_BUS(qbus);
>      VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(vbus);
> +    int total_notifiers = data_qps * 2 + cvq;
> +    VirtIONet *n = VIRTIO_NET(dev);
> +    int nvhosts = data_qps + cvq;
>      struct vhost_net *net;
>      int r, e, i;
>      NetClientState *peer;
> @@ -325,9 +328,14 @@ int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
>          return -ENOSYS;
>      }
>
> -    for (i = 0; i < total_queues; i++) {
> +    for (i = 0; i < nvhosts; i++) {
> +
> +        if (i < data_qps) {
> +            peer = qemu_get_peer(ncs, i);
> +        } else { /* Control Virtqueue */
> +            peer = qemu_get_peer(ncs, n->max_qps);

The field max_qps should be max_queues until the next patch, or maybe
we can reorder the commits and then rename the field before this
commit?

Same comment later on this function and in vhost_net_stop.

Thanks!

> +        }
>
> -        peer = qemu_get_peer(ncs, i);
>          net = get_vhost_net(peer);
>          vhost_net_set_vq_index(net, i * 2);
>
> @@ -340,14 +348,18 @@ int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
>          }
>       }
>
> -    r = k->set_guest_notifiers(qbus->parent, total_queues * 2, true);
> +    r = k->set_guest_notifiers(qbus->parent, total_notifiers, true);
>      if (r < 0) {
>          error_report("Error binding guest notifier: %d", -r);
>          goto err;
>      }
>
> -    for (i = 0; i < total_queues; i++) {
> -        peer = qemu_get_peer(ncs, i);
> +    for (i = 0; i < nvhosts; i++) {
> +        if (i < data_qps) {
> +            peer = qemu_get_peer(ncs, i);
> +        } else {
> +            peer = qemu_get_peer(ncs, n->max_qps);
> +        }
>          r = vhost_net_start_one(get_vhost_net(peer), dev);
>
>          if (r < 0) {
> @@ -371,7 +383,7 @@ err_start:
>          peer = qemu_get_peer(ncs , i);
>          vhost_net_stop_one(get_vhost_net(peer), dev);
>      }
> -    e = k->set_guest_notifiers(qbus->parent, total_queues * 2, false);
> +    e = k->set_guest_notifiers(qbus->parent, total_notifiers, false);
>      if (e < 0) {
>          fprintf(stderr, "vhost guest notifier cleanup failed: %d\n", e);
>          fflush(stderr);
> @@ -381,18 +393,27 @@ err:
>  }
>
>  void vhost_net_stop(VirtIODevice *dev, NetClientState *ncs,
> -                    int total_queues)
> +                    int data_qps, int cvq)
>  {
>      BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(dev)));
>      VirtioBusState *vbus = VIRTIO_BUS(qbus);
>      VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(vbus);
> +    VirtIONet *n = VIRTIO_NET(dev);
> +    NetClientState *peer;
> +    int total_notifiers = data_qps * 2 + cvq;
> +    int nvhosts = data_qps + cvq;
>      int i, r;
>
> -    for (i = 0; i < total_queues; i++) {
> -        vhost_net_stop_one(get_vhost_net(ncs[i].peer), dev);
> +    for (i = 0; i < nvhosts; i++) {
> +        if (i < data_qps) {
> +            peer = qemu_get_peer(ncs, i);
> +        } else {
> +            peer = qemu_get_peer(ncs, n->max_qps);
> +        }
> +        vhost_net_stop_one(get_vhost_net(peer), dev);
>      }
>
> -    r = k->set_guest_notifiers(qbus->parent, total_queues * 2, false);
> +    r = k->set_guest_notifiers(qbus->parent, total_notifiers, false);
>      if (r < 0) {
>          fprintf(stderr, "vhost guest notifier cleanup failed: %d\n", r);
>          fflush(stderr);
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index bd7958b9f0..614660274c 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -285,14 +285,14 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
>          }
>
>          n->vhost_started = 1;
> -        r = vhost_net_start(vdev, n->nic->ncs, queues);
> +        r = vhost_net_start(vdev, n->nic->ncs, queues, 0);
>          if (r < 0) {
>              error_report("unable to start vhost net: %d: "
>                           "falling back on userspace virtio", -r);
>              n->vhost_started = 0;
>          }
>      } else {
> -        vhost_net_stop(vdev, n->nic->ncs, queues);
> +        vhost_net_stop(vdev, n->nic->ncs, queues, 0);
>          n->vhost_started = 0;
>      }
>  }
> diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
> index fba40cf695..e656e38af9 100644
> --- a/include/net/vhost_net.h
> +++ b/include/net/vhost_net.h
> @@ -21,8 +21,10 @@ typedef struct VhostNetOptions {
>  uint64_t vhost_net_get_max_queues(VHostNetState *net);
>  struct vhost_net *vhost_net_init(VhostNetOptions *options);
>
> -int vhost_net_start(VirtIODevice *dev, NetClientState *ncs, int total_queues);
> -void vhost_net_stop(VirtIODevice *dev, NetClientState *ncs, int total_queues);
> +int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
> +                    int data_qps, int cvq);
> +void vhost_net_stop(VirtIODevice *dev, NetClientState *ncs,
> +                    int data_qps, int cvq);
>
>  void vhost_net_cleanup(VHostNetState *net);
>
> --
> 2.25.1
>