Re: [PATCH 1/1] spapr_vscsi: do not allow device hotplug

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

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 <danielhb413@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()?

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;
---

>  }
>  
>  void spapr_vscsi_create(SpaprVioBus *bus)
>