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

[KONRAD Frédéric]

On 15/04/2013 15:38, Cornelia Huck wrote:
On Sun, 14 Apr 2013 23:26:34 +0200
fred.kon...@greensocs.com wrote:
From: KONRAD Frederic <fred.kon...@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.kon...@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)