s390x/kvm: legacy_s390_alloc() only supports one allocation

s390x/kvm: legacy_s390_alloc() only supports one allocation

We always allocate at a fixed address, a second allocation can therefore
of course never work. We would simply overwrite mappings.

This can e.g. happen in s390_memory_init(), if trying to allocate more
than > 8TB. Let's just bail out, as there is no need for supporting it
(legacy handling for z/VM).

Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20180628113817.30814-2-david@redhat.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>