s390x: add css_migration_enabled to machine class

Currently the migration of the channel subsystem (css) is only partial
and is done by the virtio ccw proxies -- the only migratable css devices
existing at the moment.

With the current work on emulated and passthrough devices we need to
decouple the migration of the channel subsystem state from virtio ccw,
and have a separate section for it. A new section  however necessarily
breaks the migration compatibility.

So let us introduce a switch at the machine class, and put it in 'off'
state for now. We will turn the switch 'on' for future machines once all
preparations are met. For compatibility  machines the switch will stay
'off'.
Signed-off-by: NHalil Pasic <pasic@linux.vnet.ibm.com>
Acked-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Message-Id: <20170711145441.33925-3-pasic@linux.vnet.ibm.com>
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>

hw/s390x/s390-virtio-ccw.c

@@ -209,6 +209,7 @@ static void ccw_machine_class_init(ObjectClass *oc, void *data)
 
     s390mc->ri_allowed = true;
     s390mc->cpu_model_allowed = true;
+    s390mc->css_migration_enabled = false; /* TODO: set to true */
     mc->init = ccw_init;
     mc->reset = s390_machine_reset;
     mc->hot_add_cpu = s390_hot_add_cpu;
@@ -378,6 +379,11 @@ static const TypeInfo ccw_machine_info = {
     },
 };
 
+bool css_migration_enabled(void)
+{
+    return get_machine_class()->css_migration_enabled;
+}
+
 #define DEFINE_CCW_MACHINE(suffix, verstr, latest)                            \
     static void ccw_machine_##suffix##_class_init(ObjectClass *oc,            \
                                                   void *data)                 \
@@ -484,6 +490,10 @@ static const TypeInfo ccw_machine_info = {
 
 static void ccw_machine_2_10_instance_options(MachineState *machine)
 {
+    /*
+     * TODO Once preparations are done register vmstate for the css if
+     * css_migration_enabled().
+     */
 }
 
 static void ccw_machine_2_10_class_options(MachineClass *mc)
@@ -498,8 +508,11 @@ static void ccw_machine_2_9_instance_options(MachineState *machine)
 
 static void ccw_machine_2_9_class_options(MachineClass *mc)
 {
+    S390CcwMachineClass *s390mc = S390_MACHINE_CLASS(mc);
+
     ccw_machine_2_10_class_options(mc);
     SET_MACHINE_COMPAT(mc, CCW_COMPAT_2_9);
+    s390mc->css_migration_enabled = false;
 }
 DEFINE_CCW_MACHINE(2_9, "2.9", false);
 

include/hw/s390x/s390-virtio-ccw.h

@@ -39,6 +39,7 @@ typedef struct S390CcwMachineClass {
     /*< public >*/
     bool ri_allowed;
     bool cpu_model_allowed;
+    bool css_migration_enabled;
 } S390CcwMachineClass;
 
 /* runtime-instrumentation allowed by the machine */
@@ -46,4 +47,10 @@ bool ri_allowed(void);
 /* cpu model allowed by the machine */
 bool cpu_model_allowed(void);
 
+/**
+ * Returns true if (vmstate based) migration of the channel subsystem
+ * is enabled, false if it is disabled.
+ */
+bool css_migration_enabled(void);
+
 #endif