[RFC] adding a generic QAPI event for failed device hotunplug

[Daniel Henrique Barboza]

Hi,

Recent changes in pseries code (not yet pushed, available at David's
ppc-for-6.0) are using the QAPI event MEM_UNPLUG_ERROR to report memory
hotunplug errors in the pseries machine.

The pseries machine is also using a timeout to cancel CPU hotunplugs that
takes too long to finish (in which we're assuming a guest side error) and
it would be desirable to also send a QAPI event for this case as well.

At this moment, there is no "CPU_UNPLUG_ERROR" in QAPI (guess ACPI doesn't
need it). Before sending patches to implement this new event I had a talk
with David Gibson and he suggested that, instead of adding a new 
CPU_UNPLUG_ERROR
event, we could add a generic event (e.g. DEVICE_UNPLUG_ERROR) that can be
used by the pseries machine in both error scenarios (MEM and CPU).

This could also be used by x86 as well, although I believe the use of
MEM_UNPLUG_ERROR would need to be kept for awhile to avoid breaking ABI.


Any suggestions/comments?



Thanks,


DHB