Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

On Fri, Sep 22, 2017 at 11:16:34AM +0200, Thomas Huth wrote:
> Historically we've marked all devices as hotpluggable by default. However,
> most devices are not hotpluggable, and you also need a HotplugHandler to
> support these devices. So if the user tries to "device_add" or "device_del"
> such a non-hotpluggable device during runtime, either nothing really usable
> happens, or QEMU even crashes/aborts unexpectedly (see for example commit
> 84ebd3e8c7d4fe955b - "Mark diag288 watchdog as non-hotpluggable").
> So let's change this dangerous default behaviour and mark the devices as
> non-hotpluggable by default. Certain parent devices classes which are known
> as hotpluggable (e.g. PCI, USB, etc.) are marked with "hotpluggable = true",
> so that devices that are derived from these classes continue to work as
> expected.

I see that the discussion has moved on, but want to note here that
CPU hotplug on pseries breaks with this patch.

(qemu) device_add host-spapr-cpu-core,core-id=8,id=core8
Device 'host-powerpc64-cpu' does not support hotplugging

(qemu) device_add POWER8E_v2.1-spapr-cpu-core,id=core8,core-id=8
Device 'POWER8E_v2.1-powerpc64-cpu' does not support hotplugging

Hope I am not missing anything.

Regards,
Bharata.