Philippe Mathieu-Daudé <phi...@redhat.com> writes: > Cc'ing Markus > > On 8/20/20 9:06 PM, Daniel Henrique Barboza wrote: >> We do not implement hotplug in the vscsi bus, but we forgot to >> tell qdev about it. The result is that users are able to hotplug >> devices in the vscsi bus, the devices appear in qdev, but they >> aren't usable by the guest OS unless the user reboots it first. >> >> Setting qbus hotplug_handler to NULL will tell qdev-monitor, via >> qbus_is_hotpluggable(), that we do not support hotplug operations >> in spapr_vscsi. >> >> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1862059 >> >> Signed-off-by: Daniel Henrique Barboza <danielhb...@gmail.com> >> --- >> hw/scsi/spapr_vscsi.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/hw/scsi/spapr_vscsi.c b/hw/scsi/spapr_vscsi.c >> index d17dc03c73..57f0a1336f 100644 >> --- a/hw/scsi/spapr_vscsi.c >> +++ b/hw/scsi/spapr_vscsi.c >> @@ -1219,6 +1219,9 @@ static void spapr_vscsi_realize(SpaprVioDevice *dev, >> Error **errp) >> >> scsi_bus_new(&s->bus, sizeof(s->bus), DEVICE(dev), >> &vscsi_scsi_info, NULL); >> + >> + /* ibmvscsi SCSI bus does not allow hotplug. */ >> + qbus_set_hotplug_handler(BUS(&s->bus), NULL); > > Can't this be a problem later in DeviceClass::unrealize()?
Can't say offhand. Cc'ing QOM maintainers for actual expertise. A quick grep coughs up virtio_serial_device_realize() / virtio_serial_device_unrealize(), which set and unset the hotplug handler of a bus their device provides. Not the same as the code above, just a clue that messing with a bus's hotplug handler in a realize method can work. qbus_set_hotplug_handler() is entirely undocumented. It sets a link. Might be intended for use by the device that provides the bus. > I was expecting something like, overwriting the parent bus type: > > -- >8 -- > @@ -1271,6 +1271,7 @@ static void spapr_vscsi_class_init(ObjectClass > *klass, void *data) > DeviceClass *dc = DEVICE_CLASS(klass); > SpaprVioDeviceClass *k = VIO_SPAPR_DEVICE_CLASS(klass); > > + k->bus_type = NULL; /* ibmvscsi SCSI bus does not allow hotplug. */ > k->realize = spapr_vscsi_realize; > k->reset = spapr_vscsi_reset; > k->devnode = spapr_vscsi_devnode; k->bus_type does not exist. Do you mean dc->bus_type? TYPE_VIO_SPAPR_VSCSI_DEVICE is a subtype of TYPE_VIO_SPAPR_DEVICE is a subtype of TYPE_DEVICE. TYPE_DEVICE is bus-less, i.e. (concrete) instances do not plug into a bus. TYPE_VIO_SPAPR_DEVICE has bus_type TYPE_SPAPR_VIO_BUS, i.e. (concrete) instances plug into a TYPE_SPAPR_VIO_BUS. Both hot and cold plug. Zapping TYPE_VIO_SPAPR_VSCSI_DEVICE's bus_type makes it bus-less. I doubt that's okay. Also, it's not just about hot plug. What are you trying to accomplish?
