KVM: s390: implement CPU model only facilities

Some facilities should only be provided to the guest, if they are
enabled by a CPU model. This allows us to avoid capabilities and
to simply fall back to the cpumodel for deciding about a facility
without enabling it for older QEMUs or QEMUs without a CPU
model.

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

arch/s390/tools/gen_facilities.c

@@ -62,6 +62,13 @@ static struct facility_def facility_defs[] = {
 		}
 	},
 	{
+		/*
+		 * FACILITIES_KVM contains the list of facilities that are part
+		 * of the default facility mask and list that are passed to the
+		 * initial CPU model. If no CPU model is used, this, together
+		 * with the non-hypervisor managed bits, is the maximum list of
+		 * guest facilities supported by KVM.
+		 */
 		.name = "FACILITIES_KVM",
 		.bits = (int[]){
 			0,  /* N3 instructions */
@@ -89,6 +96,19 @@ static struct facility_def facility_defs[] = {
 			-1  /* END */
 		}
 	},
+	{
+		/*
+		 * FACILITIES_KVM_CPUMODEL contains the list of facilities
+		 * that can be enabled by CPU model code if the host supports
+		 * it. These facilities are not passed to the guest without
+		 * CPU model support.
+		 */
+
+		.name = "FACILITIES_KVM_CPUMODEL",
+		.bits = (int[]){
+			-1  /* END */
+		}
+	},
 };
 
 static void print_facility_list(struct facility_def *def)