libxl: introduce LIBXL_VGA_INTERFACE_TYPE_UNKNOWN

And use it as the default value for the VGA kind. This allows libxl to set
it to the default value later on when the domain type is known. For HVM
guests the default value is LIBXL_VGA_INTERFACE_TYPE_CIRRUS while for
HVMlite the default value is LIBXL_VGA_INTERFACE_TYPE_NONE.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

tools/libxl/libxl.h

@@ -922,6 +922,16 @@ void libxl_mac_copy(libxl_ctx *ctx, libxl_mac *dst, libxl_mac *src);
         ERROR_CHECKPOINT_DEVICE_NOT_SUPPORTED
 #endif
 
+/*
+ * LIBXL_HAVE_VGA_INTERFACE_TYPE_UNKNOWN
+ *
+ * In the case that LIBXL_HAVE_VGA_INTERFACE_TYPE_UNKNOWN is set the
+ * libxl_vga_interface_type enumeration type contains a
+ * LIBXL_VGA_INTERFACE_TYPE_UNKNOWN identifier. This is used to signal
+ * that a libxl_vga_interface_type type has not been initialized yet.
+ */
+#define LIBXL_HAVE_VGA_INTERFACE_TYPE_UNKNOWN 1
+
 typedef char **libxl_string_list;
 void libxl_string_list_dispose(libxl_string_list *sl);
 int libxl_string_list_length(const libxl_string_list *sl);

tools/libxl/libxl_create.c

@@ -222,8 +222,12 @@ int libxl__domain_build_info_setdefault(libxl__gc *gc,
         if (b_info->u.hvm.mmio_hole_memkb == LIBXL_MEMKB_DEFAULT)
             b_info->u.hvm.mmio_hole_memkb = 0;
 
-        if (!b_info->u.hvm.vga.kind)
-            b_info->u.hvm.vga.kind = LIBXL_VGA_INTERFACE_TYPE_CIRRUS;
+        if (b_info->u.hvm.vga.kind == LIBXL_VGA_INTERFACE_TYPE_UNKNOWN) {
+            if (b_info->device_model_version == LIBXL_DEVICE_MODEL_VERSION_NONE)
+                b_info->u.hvm.vga.kind = LIBXL_VGA_INTERFACE_TYPE_NONE;
+            else
+                b_info->u.hvm.vga.kind = LIBXL_VGA_INTERFACE_TYPE_CIRRUS;
+        }
 
         if (!b_info->u.hvm.hdtype)
             b_info->u.hvm.hdtype = LIBXL_HDTYPE_IDE;
@@ -257,6 +261,11 @@ int libxl__domain_build_info_setdefault(libxl__gc *gc,
             }
             break;
         case LIBXL_DEVICE_MODEL_VERSION_NONE:
+            if (b_info->u.hvm.vga.kind != LIBXL_VGA_INTERFACE_TYPE_NONE) {
+                LOG(ERROR,
+        "guests without a device model cannot have an emulated video card");
+                return ERROR_INVAL;
+            }
             b_info->video_memkb = 0;
             break;
         case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN:

tools/libxl/libxl_dm.c

@@ -531,6 +531,9 @@ static int libxl__build_device_model_args_old(libxl__gc *gc,
             break;
         case LIBXL_VGA_INTERFACE_TYPE_QXL:
             break;
+        default:
+            LOG(ERROR, "Invalid emulated video card specified");
+            return ERROR_INVAL;
         }
 
         if (b_info->u.hvm.boot) {
@@ -1108,6 +1111,9 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
                 GCSPRINTF("qxl-vga,vram_size_mb=%"PRIu64",ram_size_mb=%"PRIu64,
                 (b_info->video_memkb/2/1024), (b_info->video_memkb/2/1024) ) );
             break;
+        default:
+            LOG(ERROR, "Invalid emulated video card specified");
+            return ERROR_INVAL;
         }
 
         if (b_info->u.hvm.boot) {

tools/libxl/libxl_types.idl

@@ -204,11 +204,12 @@ libxl_shutdown_reason = Enumeration("shutdown_reason", [
     ], init_val = "LIBXL_SHUTDOWN_REASON_UNKNOWN")
 
 libxl_vga_interface_type = Enumeration("vga_interface_type", [
+    (0, "UNKNOWN"),
     (1, "CIRRUS"),
     (2, "STD"),
     (3, "NONE"),
     (4, "QXL"),
-    ], init_val = "LIBXL_VGA_INTERFACE_TYPE_CIRRUS")
+    ], init_val = "LIBXL_VGA_INTERFACE_TYPE_UNKNOWN")
 
 libxl_vendor_device = Enumeration("vendor_device", [
     (0, "NONE"),