virtualisation-options: init

see header comment in virtualisation-options.nix

nixos/modules/virtualisation/qemu-vm.nix

@@ -325,11 +325,15 @@ let
     OVMF = cfg.efi.OVMF;
   };
 
+  virtualisationOptions = import ./virtualisation-options.nix;
+
 in
 
 {
   imports = [
+    ./virtualisation-options.nix
     ../profiles/qemu-guest.nix
+    virtualisationOptions.diskSize
     (mkRenamedOptionModule
       [
         "virtualisation"
@@ -385,14 +389,6 @@ in
       '';
     };
 
-    virtualisation.diskSize = mkOption {
-      type = types.ints.positive;
-      default = 1024;
-      description = ''
-        The disk size in megabytes of the virtual machine.
-      '';
-    };
-
     virtualisation.diskImage = mkOption {
       type = types.nullOr types.str;
       default = "./${config.system.name}.qcow2";
@@ -1238,6 +1234,8 @@ in
     # override by setting `virtualisation.fileSystems = lib.mkForce { };`.
     fileSystems = lib.mkIf (cfg.fileSystems != { }) (mkVMOverride cfg.fileSystems);
 
+    virtualisation.diskSizeAutoSupported = false;
+
     virtualisation.fileSystems =
       let
         mkSharedDir = tag: share: {