Re: [Qemu-devel] [PATCH v3 5/8] virtio-ccw: cleanup.

[Cornelia Huck]

On Sun, 14 Apr 2013 23:26:34 +0200
address@hidden wrote:

> From: KONRAD Frederic <address@hidden>
> 
> This is a cleanup for virtio-ccw.
> The init function is replaced by the device_plugged callback from
> virtio-bus.

Hm, so you replaced a callback that might return an error by another
one that can't...

> 
> Signed-off-by: KONRAD Frederic <address@hidden>
> ---
>  hw/s390x/virtio-ccw.c | 34 ++++++++++++++--------------------
>  1 file changed, 14 insertions(+), 20 deletions(-)
> 
> diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
> index 5d62606..4857f97 100644
> --- a/hw/s390x/virtio-ccw.c
> +++ b/hw/s390x/virtio-ccw.c
> @@ -392,8 +392,10 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
>      return ret;
>  }
> 
> -static int virtio_ccw_device_init(VirtioCcwDevice *dev, VirtIODevice *vdev)
> +/* This is called by virtio-bus just after the device is plugged. */
> +static void virtio_ccw_device_plugged(DeviceState *d)
>  {
> +    VirtioCcwDevice *dev = VIRTIO_CCW_DEVICE(d);
>      unsigned int cssid = 0;
>      unsigned int ssid = 0;
>      unsigned int schid;
> @@ -401,7 +403,6 @@ static int virtio_ccw_device_init(VirtioCcwDevice *dev, 
> VirtIODevice *vdev)
>      bool have_devno = false;
>      bool found = false;
>      SubchDev *sch;
> -    int ret;
>      int num;
>      DeviceState *parent = DEVICE(dev);
> 
> @@ -410,7 +411,7 @@ static int virtio_ccw_device_init(VirtioCcwDevice *dev, 
> VirtIODevice *vdev)
>      sch->driver_data = dev;
>      dev->sch = sch;
> 
> -    dev->vdev = vdev;
> +    dev->vdev = dev->bus.vdev;
>      dev->indicators = 0;
> 
>      /* Initialize subchannel structure. */
> @@ -425,19 +426,16 @@ static int virtio_ccw_device_init(VirtioCcwDevice *dev, 
> VirtIODevice *vdev)
>          num = sscanf(dev->bus_id, "%x.%x.%04x", &cssid, &ssid, &devno);
>          if (num == 3) {
>              if ((cssid > MAX_CSSID) || (ssid > MAX_SSID)) {
> -                ret = -EINVAL;
>                  error_report("Invalid cssid or ssid: cssid %x, ssid %x",
>                               cssid, ssid);
>                  goto out_err;
>              }
>              /* Enforce use of virtual cssid. */
>              if (cssid != VIRTUAL_CSSID) {
> -                ret = -EINVAL;
>                  error_report("cssid %x not valid for virtio devices", cssid);
>                  goto out_err;
>              }
>              if (css_devno_used(cssid, ssid, devno)) {
> -                ret = -EEXIST;
>                  error_report("Device %x.%x.%04x already exists", cssid, ssid,
>                               devno);
>                  goto out_err;
> @@ -447,7 +445,6 @@ static int virtio_ccw_device_init(VirtioCcwDevice *dev, 
> VirtIODevice *vdev)
>              sch->devno = devno;
>              have_devno = true;
>          } else {
> -            ret = -EINVAL;
>              error_report("Malformed devno parameter '%s'", dev->bus_id);
>              goto out_err;
>          }
> @@ -464,7 +461,6 @@ static int virtio_ccw_device_init(VirtioCcwDevice *dev, 
> VirtIODevice *vdev)
>              }
>          }
>          if (!found) {
> -            ret = -ENODEV;
>              error_report("No free subchannel found for %x.%x.%04x", cssid, 
> ssid,
>                           devno);
>              goto out_err;
> @@ -488,7 +484,6 @@ static int virtio_ccw_device_init(VirtioCcwDevice *dev, 
> VirtIODevice *vdev)
>                          if (devno == MAX_SCHID) {
>                              devno = 0;
>                          } else if (devno == schid - 1) {
> -                            ret = -ENODEV;
>                              error_report("No free devno found");
>                              goto out_err;
>                          } else {
> @@ -506,7 +501,6 @@ static int virtio_ccw_device_init(VirtioCcwDevice *dev, 
> VirtIODevice *vdev)
>              }
>          }
>          if (!found) {
> -            ret = -ENODEV;
>              error_report("Virtual channel subsystem is full!");
>              goto out_err;
>          }
> @@ -525,20 +519,19 @@ static int virtio_ccw_device_init(VirtioCcwDevice *dev, 
> VirtIODevice *vdev)
>      sch->id.cu_type = VIRTIO_CCW_CU_TYPE;
>      sch->id.cu_model = dev->vdev->device_id;
> 
> -    virtio_bind_device(vdev, &virtio_ccw_bindings, DEVICE(dev));
>      /* Only the first 32 feature bits are used. */
> -    dev->host_features[0] = vdev->get_features(vdev, dev->host_features[0]);
> +    dev->host_features[0] = dev->vdev->get_features(dev->vdev,
> +                                                    dev->host_features[0]);
>      dev->host_features[0] |= 0x1 << VIRTIO_F_NOTIFY_ON_EMPTY;
>      dev->host_features[0] |= 0x1 << VIRTIO_F_BAD_FEATURE;
> 
>      css_generate_sch_crws(sch->cssid, sch->ssid, sch->schid,
>                            parent->hotplugged, 1);
> -    return 0;
> +    return;
> 
>  out_err:
>      dev->sch = NULL;
>      g_free(sch);
> -    return ret;

What happens here? We now have a VirtioCcwDevice without an associated
subchannel device (i. e. no way to do any I/O). With the old code, we'd
just have failed initializing the virtio device, but now we have a
useless device laying around.

>  }
> 
>  static int virtio_ccw_exit(VirtioCcwDevice *dev)