[Qemu-devel] block ais migration for machines <= 2.9

[Christian Borntraeger]

Something like the following seems to do the tricks.
Needs proper patch description, review, full test with different kernel 
versions.....

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 1c7af39..2ff32ba 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -212,6 +212,7 @@ static void ccw_machine_class_init(ObjectClass *oc, void 
*data)
     s390mc->cpu_model_allowed = true;
     s390mc->css_migration_enabled = true;
     s390mc->gs_allowed = true;
+    s390mc->ais_allowed = true;
     mc->init = ccw_init;
     mc->reset = s390_machine_reset;
     mc->hot_add_cpu = s390_hot_add_cpu;
@@ -305,6 +306,11 @@ bool gs_allowed(void)
     return false;
 }
 
+bool ais_allowed(void)
+{
+    return get_machine_class()->ais_allowed;
+}
+
 static char *machine_get_loadparm(Object *obj, Error **errp)
 {
     S390CcwMachineState *ms = S390_CCW_MACHINE(obj);
@@ -533,6 +539,7 @@ static void ccw_machine_2_9_class_options(MachineClass *mc)
     S390CcwMachineClass *s390mc = S390_MACHINE_CLASS(mc);
 
     s390mc->gs_allowed = false;
+    s390mc->ais_allowed = false;
     ccw_machine_2_10_class_options(mc);
     SET_MACHINE_COMPAT(mc, CCW_COMPAT_2_9);
     s390mc->css_migration_enabled = false;
diff --git a/include/hw/s390x/s390-virtio-ccw.h 
b/include/hw/s390x/s390-virtio-ccw.h
index 41a9d28..bba8660 100644
--- a/include/hw/s390x/s390-virtio-ccw.h
+++ b/include/hw/s390x/s390-virtio-ccw.h
@@ -41,6 +41,7 @@ typedef struct S390CcwMachineClass {
     bool cpu_model_allowed;
     bool css_migration_enabled;
     bool gs_allowed;
+    bool ais_allowed;
 } S390CcwMachineClass;
 
 /* runtime-instrumentation allowed by the machine */
@@ -49,6 +50,8 @@ bool ri_allowed(void);
 bool cpu_model_allowed(void);
 /* guarded-storage allowed by the machine */
 bool gs_allowed(void);
+/* ais allowed by the machine */
+bool ais_allowed(void);
 
 /**
  * Returns true if (vmstate based) migration of the channel subsystem
diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
index c4c5791..531d474 100644
--- a/target/s390x/kvm.c
+++ b/target/s390x/kvm.c
@@ -309,7 +309,9 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
     }
 
     /* Try to enable AIS facility */
-    kvm_vm_enable_cap(s, KVM_CAP_S390_AIS, 0);
+    if (ais_allowed()) {
+       kvm_vm_enable_cap(s, KVM_CAP_S390_AIS, 0);
+    }
 
     qemu_mutex_init(&qemu_sigp_mutex);