s390x/cpumodel: Set up CPU model for AQIC interception

s390x/cpumodel: Set up CPU model for AQIC interception

Let's add support for the AP-Queue interruption facility to the CPU
model.

The S390_FEAT_AP_QUEUE_INTERRUPT_CONTROL, CPU facility indicates
whether the PQAP instruction with the AQIC command is available
to the guest.
This feature will be enabled only if the AP instructions are
available on the linux host and AQIC facility is installed on
the host.

This feature must be turned on from userspace to intercept AP
instructions on the KVM guest. The QEMU command line to turn
this feature on looks something like this:

    qemu-system-s390x ... -cpu xxx,apqi=on ...
or
    ... -cpu host

Right now AP pass-through devices do not support migration,
which means that we do not have to take care of migrating
the interrupt data:
virsh migrate apguest --live qemu+ssh://root@target.lan/system
error: Requested operation is not valid: domain has assigned non-USB host devices

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
[rebase to newest qemu and fixup description]
Message-Id: <20190705153249.12525-1-borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>