Re: [Qemu-devel] [PULL 12/47] virtio: remove ioeventfd_disabled altogether

[Christian Borntraeger]

On 10/30/2016 10:23 PM, Michael S. Tsirkin wrote:
> From: Paolo Bonzini <address@hidden>
> 
> Now that there is not anymore a switch from the generic ioeventfd handler
> to the dataplane handler, virtio_bus_set_host_notifier(assign=true) is
> always called with !bus->ioeventfd_started, hence virtio_bus_stop_ioeventfd
> does nothing in this case.  Move the invocation to vhost.c, which is the
> only place that needs it.
> 
> Reviewed-by: Cornelia Huck <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>
> Reviewed-by: Michael S. Tsirkin <address@hidden>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
>  include/hw/virtio/virtio-bus.h |  6 ------
>  hw/virtio/vhost.c              |  3 +++
>  hw/virtio/virtio-bus.c         | 23 ++++++++---------------
>  3 files changed, 11 insertions(+), 21 deletions(-)

This breaks vhost-net for s390/kvm after rebooting the guest. (ping fails and
ifconfig shows no packets is TXed)

Any idea?

> 
> diff --git a/include/hw/virtio/virtio-bus.h b/include/hw/virtio/virtio-bus.h
> index af6b5c4..cbdf745 100644
> --- a/include/hw/virtio/virtio-bus.h
> +++ b/include/hw/virtio/virtio-bus.h
> @@ -94,12 +94,6 @@ struct VirtioBusState {
>      BusState parent_obj;
> 
>      /*
> -     * Set if the default ioeventfd handlers are disabled by vhost
> -     * or dataplane.
> -     */
> -    bool ioeventfd_disabled;
> -
> -    /*
>       * Set if ioeventfd has been started.
>       */
>      bool ioeventfd_started;
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 501a5f4..131f164 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -1196,6 +1196,7 @@ int vhost_dev_enable_notifiers(struct vhost_dev *hdev, 
> VirtIODevice *vdev)
>          goto fail;
>      }
> 
> +    virtio_device_stop_ioeventfd(vdev);
>      for (i = 0; i < hdev->nvqs; ++i) {
>          r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), hdev->vq_index + 
> i,
>                                           true);
> @@ -1215,6 +1216,7 @@ fail_vq:
>          }
>          assert (e >= 0);
>      }
> +    virtio_device_start_ioeventfd(vdev);
>  fail:
>      return r;
>  }
> @@ -1237,6 +1239,7 @@ void vhost_dev_disable_notifiers(struct vhost_dev 
> *hdev, VirtIODevice *vdev)
>          }
>          assert (r >= 0);
>      }
> +    virtio_device_start_ioeventfd(vdev);
>  }
> 
>  /* Test and clear event pending status.
> diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
> index a619445..b0e4544 100644
> --- a/hw/virtio/virtio-bus.c
> +++ b/hw/virtio/virtio-bus.c
> @@ -190,7 +190,7 @@ int virtio_bus_start_ioeventfd(VirtioBusState *bus)
>      if (!k->ioeventfd_assign || !k->ioeventfd_enabled(proxy)) {
>          return -ENOSYS;
>      }
> -    if (bus->ioeventfd_started || bus->ioeventfd_disabled) {
> +    if (bus->ioeventfd_started) {
>          return 0;
>      }
>      r = vdc->start_ioeventfd(vdev);
> @@ -226,8 +226,8 @@ bool virtio_bus_ioeventfd_enabled(VirtioBusState *bus)
>  }
> 
>  /*
> - * This function switches from/to the generic ioeventfd handler.
> - * assign==false means 'use generic ioeventfd handler'.
> + * This function switches ioeventfd on/off in the device.
> + * The caller must set or clear the handlers for the EventNotifier.
>   */
>  int virtio_bus_set_host_notifier(VirtioBusState *bus, int n, bool assign)
>  {
> @@ -237,19 +237,12 @@ int virtio_bus_set_host_notifier(VirtioBusState *bus, 
> int n, bool assign)
>      if (!k->ioeventfd_assign) {
>          return -ENOSYS;
>      }
> -    bus->ioeventfd_disabled = assign;
>      if (assign) {
> -        /*
> -         * Stop using the generic ioeventfd, we are doing eventfd handling
> -         * ourselves below
> -         *
> -         * FIXME: We should just switch the handler and not deassign the
> -         * ioeventfd.
> -         * Otherwise, there's a window where we don't have an
> -         * ioeventfd and we may end up with a notification where
> -         * we don't expect one.
> -         */
> -        virtio_bus_stop_ioeventfd(bus);
> +        assert(!bus->ioeventfd_started);
> +    } else {
> +        if (!bus->ioeventfd_started) {
> +            return 0;
> +        }
>      }
>      return set_host_notifier_internal(proxy, bus, n, assign);
>  }
>