[Qemu-ppc] [PATCH] spapr: Forbid setting ic-mode for old machine types

[Greg Kurz]

Machine types 3.0 and older only know about the legacy XICS backend.
Make it clear by erroring out if the user tries to set ic-mode on
such machines.

Signed-off-by: Greg Kurz <address@hidden>
---

Motivation for this comes from a failing backward migration test, caused
by ic-mode=xics I forgot to drop from the command line :)
---
 hw/ppc/spapr.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 0942f35bf87e..6b8dbf5c5a3c 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -3126,6 +3126,11 @@ static void spapr_set_ic_mode(Object *obj, const char 
*value, Error **errp)
 {
     sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
 
+    if (SPAPR_MACHINE_GET_CLASS(spapr)->legacy_irq_allocation) {
+        error_setg(errp, "This machine only uses the legacy XICS backend, 
don't pass ic-mode");
+        return;
+    }
+
     /* The legacy IRQ backend can not be set */
     if (strcmp(value, "xics") == 0) {
         spapr->irq = &spapr_irq_xics;