[Qemu-ppc] [PATCH 2/3] spapr: don't migrate "spapr_option_vector_ov5_cas" to pre 2.8 machines

[Greg Kurz]

a324d6f16697 "spapr: Support ibm,dynamic-memory-v2 property" added
a new feature in the set of CAS-negotiatable options. This causes
the CAS-negotiated options subsection to be migrated, even for old
machine types that don't know about it, and breaks backward migration
to QEMU 2.7 and older versions:

qemu-system-ppc64: error while loading state for instance 0x0 of device
 'spapr'
qemu-system-ppc64: load of migration failed: No such file or directory

Since this feature only affects boot time behaviour, it should be
filtered out when we decide to migrate CAS-negotiated options, like
we already do with OV5_FORM1_AFFINITY and OV5_DRCONF_MEMORY.

Signed-off-by: Greg Kurz <address@hidden>
---
 hw/ppc/spapr.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index b35aff5d811c..eb9d087d1a60 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1851,10 +1851,12 @@ static bool spapr_ov5_cas_needed(void *opaque)
      *
      * Thus, for any cases where the set of available CAS-negotiatable
      * options extends beyond OV5_FORM1_AFFINITY and OV5_DRCONF_MEMORY, we
-     * include the CAS-negotiated options in the migration stream.
+     * include the CAS-negotiated options in the migration stream, unless
+     * if they affect boot time behaviour only.
      */
     spapr_ovec_set(ov5_mask, OV5_FORM1_AFFINITY);
     spapr_ovec_set(ov5_mask, OV5_DRCONF_MEMORY);
+    spapr_ovec_set(ov5_mask, OV5_DRMEM_V2);
 
     /* spapr_ovec_diff returns true if bits were removed. we avoid using
      * the mask itself since in the future it's possible "legacy" bits may be