CP-18860 check memory range before VM.start when using nested virt

When using nested_virtualisation, the VM cannot use a dynamic memory
range. We can detect this only before the VM starts and not when the
memory is set because there many path can lead to this situation:

(1) set memory range (ok), set nested_virt - now illegal
(2) set nested_virt (ok), set memory range - now illegal

Hence, we accept that nested virt and memory range can be in an
inconsistent state temporarily but check before the VM is started.

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

CP-18860 use xapi_vm_memory_constraints

This commits changes the implementation to use the
xapi_vm_memory_constraints module to check memory constraints when a VM
uses nested_virt. Previously a new error message and custom check was
used.

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

Author: lindig

ocaml/idl/datamodel.ml

@@ -511,6 +511,8 @@ let _ =
     ~doc:"You attempted an operation which would have resulted in duplicate keys in the database." ();
   error Api_errors.location_not_unique ["SR"; "location"]
     ~doc:"A VDI with the specified location already exists within the SR" ();
+  error Api_errors.memory_constraint_violation ["constraint"]
+    ~doc:"The dynamic memory range does not satisfy the following constraint." (); 
 
   (* Session errors *)
   error Api_errors.session_authentication_failed []

ocaml/xapi/xapi_vm_lifecycle.ml

@@ -371,18 +371,6 @@ 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.   *)

ocaml/xapi/xapi_vm_memory_constraints.ml

@@ -51,19 +51,22 @@ module Vm_memory_constraints : T = struct
 
   include Vm_memory_constraints.Vm_memory_constraints
 
+  let order_constraint =
+    "Memory limits must satisfy: \
+     static_min ≤ dynamic_min ≤ dynamic_max ≤ static_max"
+  let equality_constraint =
+    "Memory limits must satisfy: \
+     static_min ≤ dynamic_min = dynamic_max = static_max"
+
   let assert_valid ~constraints =
     if not (are_valid ~constraints)
     then raise (Api_errors.Server_error (
-        Api_errors.memory_constraint_violation,
-        ["Memory limits must satisfy: \
-          				static_min ≤ dynamic_min ≤ dynamic_max ≤ static_max"]))
+      Api_errors.memory_constraint_violation, [order_constraint]))
 
   let assert_valid_and_pinned_at_static_max ~constraints =
     if not (are_valid_and_pinned_at_static_max ~constraints)
     then raise (Api_errors.Server_error (
-        Api_errors.memory_constraint_violation,
-        ["Memory limits must satisfy: \
-          				static_min ≤ dynamic_min = dynamic_max = static_max"]))
+      Api_errors.memory_constraint_violation, [equality_constraint]))
 
   let assert_valid_for_current_context ~__context ~vm ~constraints =
     let is_control_domain = Db.VM.get_is_control_domain ~__context ~self:vm in

ocaml/xapi/xapi_xenops.ml

@@ -708,6 +708,16 @@ module MD = struct
     (* CA-55754: temporarily disable msitranslate when GPU is passed through. *)
     let pci_msitranslate =
       if vm.API.vM_VGPUs <> [] then false else pci_msitranslate in
+
+    (* CP-18860: check memory limits if using nested_virt *)
+    if Vm_platform.is_true ~key:"nested-virt" ~platformdata ~default:false
+    then
+      begin
+        let module C = Xapi_vm_memory_constraints.Vm_memory_constraints in
+        let c = C.get ~__context ~vm_ref:vmref in
+        C.assert_valid_and_pinned_at_static_max c
+      end;
+
     {
       id = vm.API.vM_uuid;
       name = vm.API.vM_name_label;