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

["KONRAD Frédéric" <fred.konrad@greensocs.com>]

On 15/04/2013 15:38, Cornelia Huck wrote:
> On Sun, 14 Apr 2013 23:26:34 +0200
> fred.konrad@greensocs.com wrote:
>
>> From: KONRAD Frederic <fred.konrad@greensocs.com>
>>
>> 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...
Yes, I think this is not the right thing to do.

Originally, virtio-device was able to be hot-plugged in virtio-bus, 
that's why I
used this callback.

So two solutions,
     * Leave the init function as this.
     * Modify the callback prototype (returning the error).

And probably do the same with PCI and S390.

What do you think is the best?

Thanks,
Fred

>
>> Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
>> ---
>>   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)