[Qemu-devel] [PATCH] hw/ppc/spapr: Use POWER8 by default for the pseries-2.8 machine

[Thomas Huth <thuth@redhat.com>]

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. Due to this reason, the linux-user
target already switched to POWER8 by default a while ago (see commit
de3f1b98410e0d5b406a0df3a48547b559d18602). Since the softmmu target
of course has the same problem, we should switch there to POWER8
by default for the newer machine types, too.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1357808
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 Note: This patch should be applied on top of David's ppc-for-2.8
 tree, since the pseries-2.8 machine has just been added there
 recently.

 hw/ppc/spapr.c         | 11 ++++++++++-
 include/hw/ppc/spapr.h |  1 +
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 63b6a0d..799bcff 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1775,7 +1775,13 @@ static void ppc_spapr_init(MachineState *machine)
 
     /* init CPUs */
     if (machine->cpu_model == NULL) {
-        machine->cpu_model = kvm_enabled() ? "host" : "POWER7";
+        if (kvm_enabled()) {
+            machine->cpu_model = "host";
+        } else if (smc->tcg_default_cpu) {
+            machine->cpu_model = smc->tcg_default_cpu;
+        } else {
+            machine->cpu_model = "POWER8";
+        }
     }
 
     ppc_cpu_parse_features(machine->cpu_model);
@@ -2478,7 +2484,10 @@ 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);
 }
 
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 6289d50..39dadaa 100644
--- a/include/hw/ppc/spapr.h
+++ b/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 */
 };
 
 /**
-- 
1.8.3.1