KVM: s390: define GISA format-0 data structure

In preperation to support pass-through adapter interrupts, the Guest
Interruption State Area (GISA) and the Adapter Interruption Virtualization
(AIV) features will be introduced here.

This patch introduces format-0 GISA (that is defines the struct describing
the GISA, allocates storage for it, and introduces fields for the
GISA address in kvm_s390_sie_block and kvm_s390_vsie).

As the GISA requires storage below 2GB, it is put in sie_page2, which is
already allocated in ZONE_DMA. In addition, The GISA requires alignment to
its integral boundary. This is already naturally aligned via the
padding in the sie_page2.

Signed-off-by: Michael Mueller <mimu@linux.vnet.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

arch/s390/kvm/kvm-s390.c

@@ -1928,6 +1928,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	if (!kvm->arch.dbf)
 		goto out_err;
 
+	BUILD_BUG_ON(sizeof(struct sie_page2) != 4096);
 	kvm->arch.sie_page2 =
 	     (struct sie_page2 *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
 	if (!kvm->arch.sie_page2)