libvirt users - Oct 2018 - Re: Device lease hot unplug and events

Hi, when working on hot unplugs of various devices, I've found out that
hot unplugging <lease> device doesn't generate
VIR_DOMAIN_EVENT_ID_DEVICE_REMOVED event.  <lease> also doesn't have
an
alias, so it wouldn't be identifiable in the corresponding callback.

Is this difference from other hotpluggable devices intentional?  If yes,
is there any better way of checking that <lease> removal is completed
than querying and examining the domain XML?  From user's point of view,
it would be best if I could simply handle the device removal event the
same way as with other devices.

Thanks,
Milan

On Fri, Oct 12, 2018 at 19:33:54 +0200, Milan Zamazal
wrote:
> Hi, when working on hot unplugs of various devices, I've found out that
> hot unplugging <lease> device doesn't generate
> VIR_DOMAIN_EVENT_ID_DEVICE_REMOVED event.  <lease> also doesn't
have an
> alias, so it wouldn't be identifiable in the corresponding callback.
> 
> Is this difference from other hotpluggable devices intentional?  If yes,
Well a "lease" is not a device per-se. It's just libvirt putting
it with
devices. Currently the "lease" is always successfully
removed/unplugged
if the API returns success as there is no cooperation with qemu
necessary so the semantics of asking the guest OS to do something don't
apply.
> is there any better way of checking that <lease> removal is completed
> than querying and examining the domain XML?  From user's point of view,
> it would be best if I could simply handle the device removal event the
> same way as with other devices.
Yes, we probably should add the event and synthetize it for "lease"
since we will not get one from qemu. Also we'll need to add alias for
the lease so that the event can be used.

Peter Krempa <pkrempa@redhat.com> writes:
> On Fri, Oct 12, 2018 at 19:33:54 +0200, Milan Zamazal wrote:
>> Hi, when working on hot unplugs of various devices, I've found out
that
>> hot unplugging <lease> device doesn't generate
>> VIR_DOMAIN_EVENT_ID_DEVICE_REMOVED event.  <lease> also
doesn't have an
>> alias, so it wouldn't be identifiable in the corresponding
callback.
>> 
>> Is this difference from other hotpluggable devices intentional?  If
yes,
>
> Well a "lease" is not a device per-se. It's just libvirt
putting it with
> devices. Currently the "lease" is always successfully
removed/unplugged
> if the API returns success as there is no cooperation with qemu
> necessary so the semantics of asking the guest OS to do something don't
> apply.
I see, thank you for explanation.  Can we rely on the fact that lease
removal is and remains synchronous or is it a property that can change
in the future?
>> is there any better way of checking that <lease> removal is
completed
>> than querying and examining the domain XML?  From user's point of
view,
>> it would be best if I could simply handle the device removal event the
>> same way as with other devices.
>
> Yes, we probably should add the event and synthetize it for
"lease"
> since we will not get one from qemu. Also we'll need to add alias for
> the lease so that the event can be used.
Since this is what an uninformed user expects (and I believe libvirt
documentation doesn't contradict), I'd like to have the event + alias.
Should I file a corresponding bug or RFE?

Thanks,
Milan