CP-18860 re-factor is_mobile() into nomigrate() and nested_virt()

We want to create more predicates over the value of nomigrate and
nested_virt without duplicating code. By exposing nomigrate and
nested_virt this now becomes possible.

Unit tests show that the semantics of is_mobile are unchanged.

Signed-off-by: Christian Lindig <christian.lindig@citrix.com>

Author: lindig

ocaml/xapi/xapi_vm_lifecycle.ml

@@ -279,18 +279,28 @@ let check_protection_policy ~vmr ~op ~ref_str =
  * If the VM_metrics object does not exist, it implies the VM is not
  * running - in which case we use the current values from the database.
  **)
-let is_mobile ~__context vm strict =
-  let metrics = Db.VM.get_metrics ~__context ~self:vm in
+
+let nomigrate ~__context vm metrics =
   try
-    let nomigrate   = Db.VM_metrics.get_nomigrate ~__context ~self:metrics in
-    let nested_virt = Db.VM_metrics.get_nested_virt ~__context ~self:metrics in
-    (not nomigrate && not nested_virt) || not strict
+    Db.VM_metrics.get_nomigrate ~__context ~self:metrics
   with _ ->
-    (* No VM_metrics *)
-    let not_true platformdata key =
-      not @@ Vm_platform.is_true ~key ~platformdata ~default:false in
-    let platform = Db.VM.get_platform ~__context ~self:vm in
-    (not_true platform "nomigrate" && not_true platform "nested-virt") || not strict
+    let platformdata = Db.VM.get_platform ~__context ~self:vm in
+    let key = "nomigrate" in
+    Vm_platform.is_true ~key ~platformdata ~default:false
+
+let nested_virt ~__context vm metrics =
+  try
+    Db.VM_metrics.get_nested_virt ~__context ~self:metrics
+  with _ ->
+    let platformdata = Db.VM.get_platform ~__context ~self:vm in
+    let key = "nested-virt" in
+    Vm_platform.is_true ~key ~platformdata ~default:false
+
+let is_mobile ~__context vm strict =
+  let metrics = Db.VM.get_metrics ~__context ~self:vm in
+  (not @@ nomigrate ~__context vm metrics 
+   && not @@ nested_virt ~__context vm metrics)
+  || not strict
 
 
 (** Take an internal VM record and a proposed operation. Return None iff the operation
@@ -361,6 +371,18 @@ let check_operation_error ~__context ~vmr ~vmgmr ~ref ~clone_suspended_vm_enable
       | _ -> None
     ) in
 
+  (* CP-18860: can't set dynamic mem range when using nested virt *)
+  let current_error = check current_error (fun () ->
+      match op with
+      | `changing_dynamic_range ->
+        let metrics = Db.VM.get_metrics ~__context ~self:ref in
+        if nested_virt ~__context ref metrics then
+          Some (Api_errors.vm_cant_use_dyn_memory, [ref_str])
+        else 
+          None
+      | _ -> None
+    ) in
+
   (* Check if the VM is a control domain (eg domain 0).            *)
   (* FIXME: Instead of special-casing for the control domain here, *)
   (* make use of the Helpers.ballooning_enabled_for_vm function.   *)