[Qemu-ppc] [RFC 17/17] pseries: Default to POWER8 compatibility mode

[David Gibson]

Currently, the pseries machine defaults to running in the "raw" mode of
whatever the CPU version is - that is, without any compatibility options
enabled in the CPU.

However, migration is only really safe in "raw" mode if source and
destination have exactly the same cpu model.  Since HV KVM exposes the
version of the host CPU to the guest, that means "raw" migration between
hosts with different minor revisions isn't strictly safe, although it
generally works in practice.

To allow this sort of migration in a more clearly defined way, instead
default to running in POWER8 compatibility mode - if an older CPU is used
that will automatically be downgraded to the higest available compatibility
mode.

Signed-off-by: David Gibson <address@hidden>
---
 hw/ppc/spapr.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 2aa0900..8c18dc8 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2194,6 +2194,7 @@ static void spapr_machine_initfn(Object *obj)
                                     " (required for memory hot-unplug 
support)",
                                     NULL);
 
+    spapr->max_compat_pvr = CPU_POWERPC_LOGICAL_2_07; /* POWER8 */
     object_property_add(obj, "max-cpu-compat", "str",
                         ppc_compat_prop_get, ppc_compat_prop_set,
                         NULL, &spapr->max_compat_pvr, &error_fatal);
-- 
2.7.4