Re: [RFC PATCH v13 4/4] s390: implementing CHSC SEI for AP config change

[Matthew Rosato <mjrosato@linux.ibm.com>]

>>
>> AFAICT this portion of the handler including mutex should be moved out of ap.c into chsc_sei_nt0_get_event().  When vfio_ap is not in use, we can't call into it.  Can't you also build without VFIO_AP?  I didn't try it but that sure seems like it would cause issues too.
> 
> If that were the case, I think the checks I mentioned above would be sufficient because
> the S390_FEAT_AP feature could not be set.
> 

OK, I tested it quick (remove VFIO_AP from config) and that appears to be the case; this also restores zPCI hotplug capability since we won't call info hw/vfio/ap.c/.

> 
> What about moving lock initialization to the vfio_ap_class_init() function?
> 

I tried a quick hack of that too and it appears to work, at least for the zPCI regression (note: I did not test the AP portion).

This approach is probably not the way I would have designed it initially...  But it does seem to be the simplest thing to do from a fix perspective.  

Can you or Rorie prepare a proper patch w/ a fixes tag and send (please add me to CC). Also please test the change against the vfio-ap environment; you can also test zPCI but I would also like to run some tests.