ppc/kvm: have the "family" CPU alias to point to TYPE_HOST_POWERPC_CPU

When running KVM on POWER, we allow the user to pass "-cpu POWERx" instead
of "-cpu host". This is achieved by patching the ppc_cpu_aliases[] array
so that "POWERx" points to the CPU class with the same PVR as the host CPU.
This causes CPUs to be instantiated from this CPU class instead of the
TYPE_HOST_POWERPC_CPU class which is used with "-cpu host". These CPUs thus
miss all the KVM specific tuning from kvmppc_host_cpu_class_init().

This currently causes QEMU with "-cpu POWER9" to fail when running KVM on a
POWER9 DD1 host:

qemu-system-ppc64: Register sync failed... If you're using kvm-hv.ko, only
 "-cpu host" is possible
kvm_init_vcpu failed: Invalid argument

Let's have the "POWERx" alias to point to TYPE_HOST_POWERPC_CPU directly,
so that "-cpu POWERx" instantiates CPUs from the same class as "-cpu host".
Signed-off-by: NGreg Kurz <groug@kaod.org>
Tested-by: NLaurent Vivier <lvivier@redhat.com>
Reviewed-by: NLaurent Vivier <lvivier@redhat.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>

target/ppc/kvm.c

@@ -2445,6 +2445,7 @@ static int kvm_ppc_register_host_cpu_type(void)
         .class_init = kvmppc_host_cpu_class_init,
     };
     PowerPCCPUClass *pvr_pcc;
+    ObjectClass *oc;
     DeviceClass *dc;
     int i;
 
@@ -2455,6 +2456,9 @@ static int kvm_ppc_register_host_cpu_type(void)
     type_info.parent = object_class_get_name(OBJECT_CLASS(pvr_pcc));
     type_register(&type_info);
 
+    oc = object_class_by_name(type_info.name);
+    g_assert(oc);
+
 #if defined(TARGET_PPC64)
     type_info.name = g_strdup_printf("%s-"TYPE_SPAPR_CPU_CORE, "host");
     type_info.parent = TYPE_SPAPR_CPU_CORE,
@@ -2474,7 +2478,6 @@ static int kvm_ppc_register_host_cpu_type(void)
     dc = DEVICE_CLASS(ppc_cpu_get_family_class(pvr_pcc));
     for (i = 0; ppc_cpu_aliases[i].alias != NULL; i++) {
         if (strcmp(ppc_cpu_aliases[i].alias, dc->desc) == 0) {
-            ObjectClass *oc = OBJECT_CLASS(pvr_pcc);
             char *suffix;
 
             ppc_cpu_aliases[i].model = g_strdup(object_class_get_name(oc));