hw/ppc/spapr: Use POWER8 by default for the pseries-2.8 machine

A couple of distributors are compiling their distributions
with "-mcpu=power8" for ppc64le these days, so the user sooner
or later runs into a crash there when not explicitely specifying
the "-cpu POWER8" option to QEMU (which is currently using POWER7
for the "pseries" machine by default). Due to this reason, the
linux-user target already switched to POWER8 a while ago (see commit
de3f1b98). Since the softmmu target
of course has the same problem, we should switch there to POWER8 for
the newer machine types, too.
Signed-off-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>

hw/ppc/spapr.c

@@ -1775,7 +1775,7 @@ static void ppc_spapr_init(MachineState *machine)
 
     /* init CPUs */
     if (machine->cpu_model == NULL) {
-        machine->cpu_model = kvm_enabled() ? "host" : "POWER7";
+        machine->cpu_model = kvm_enabled() ? "host" : smc->tcg_default_cpu;
     }
 
     ppc_cpu_parse_features(machine->cpu_model);
@@ -2402,6 +2402,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
     mc->cpu_index_to_socket_id = spapr_cpu_index_to_socket_id;
 
     smc->dr_lmb_enabled = true;
+    smc->tcg_default_cpu = "POWER8";
     mc->query_hotpluggable_cpus = spapr_query_hotpluggable_cpus;
     fwc->get_dev_path = spapr_get_fw_dev_path;
     nc->nmi_monitor_handler = spapr_nmi;
@@ -2478,7 +2479,10 @@ static void spapr_machine_2_7_instance_options(MachineState *machine)
 
 static void spapr_machine_2_7_class_options(MachineClass *mc)
 {
+    sPAPRMachineClass *smc = SPAPR_MACHINE_CLASS(mc);
+
     spapr_machine_2_8_class_options(mc);
+    smc->tcg_default_cpu = "POWER7";
     SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_7);
 }
 

include/hw/ppc/spapr.h

@@ -39,6 +39,7 @@ struct sPAPRMachineClass {
     /*< public >*/
     bool dr_lmb_enabled;       /* enable dynamic-reconfig/hotplug of LMBs */
     bool use_ohci_by_default;  /* use USB-OHCI instead of XHCI */
+    const char *tcg_default_cpu; /* which (TCG) CPU to simulate by default */
 };
 
 /**