libxl: set default disk format in device post-parse

When starting a domian, a libxl_domain_config object is created from
virDomainDef. Any virDomainDiskDef devices with a format of
VIR_STORAGE_FILE_NONE are mapped to LIBXL_DISK_FORMAT_RAW in the
corresponding libxl_disk_device, but the virDomainDiskDef format is
never updated to reflect the change.

A better place to set a default format for disk devices is the
device post-parse callback, ensuring the virDomainDiskDef object
reflects the default format.

src/libxl/libxl_conf.c

@@ -765,8 +765,6 @@ libxlMakeDisk(virDomainDiskDefPtr l_disk, libxl_device_disk *x_disk)
                 x_disk->format = LIBXL_DISK_FORMAT_VHD;
                 x_disk->backend = LIBXL_DISK_BACKEND_TAP;
                 break;
-            case VIR_STORAGE_FILE_NONE:
-                /* No subtype specified, default to raw/tap */
             case VIR_STORAGE_FILE_RAW:
                 x_disk->format = LIBXL_DISK_FORMAT_RAW;
                 x_disk->backend = LIBXL_DISK_BACKEND_TAP;
@@ -802,8 +800,6 @@ libxlMakeDisk(virDomainDiskDefPtr l_disk, libxl_device_disk *x_disk)
             case VIR_STORAGE_FILE_VHD:
                 x_disk->format = LIBXL_DISK_FORMAT_VHD;
                 break;
-            case VIR_STORAGE_FILE_NONE:
-                /* No subtype specified, default to raw */
             case VIR_STORAGE_FILE_RAW:
                 x_disk->format = LIBXL_DISK_FORMAT_RAW;
                 break;
@@ -816,8 +812,7 @@ libxlMakeDisk(virDomainDiskDefPtr l_disk, libxl_device_disk *x_disk)
                 return -1;
             }
         } else if (STREQ(driver, "file")) {
-            if (format != VIR_STORAGE_FILE_NONE &&
-                format != VIR_STORAGE_FILE_RAW) {
+            if (format != VIR_STORAGE_FILE_RAW) {
                 virReportError(VIR_ERR_INTERNAL_ERROR,
                                _("libxenlight does not support disk format %s "
                                  "with disk driver %s"),
@@ -828,8 +823,7 @@ libxlMakeDisk(virDomainDiskDefPtr l_disk, libxl_device_disk *x_disk)
             x_disk->format = LIBXL_DISK_FORMAT_RAW;
             x_disk->backend = LIBXL_DISK_BACKEND_QDISK;
         } else if (STREQ(driver, "phy")) {
-            if (format != VIR_STORAGE_FILE_NONE &&
-                format != VIR_STORAGE_FILE_RAW) {
+            if (format != VIR_STORAGE_FILE_RAW) {
                 virReportError(VIR_ERR_INTERNAL_ERROR,
                                _("libxenlight does not support disk format %s "
                                  "with disk driver %s"),

src/libxl/libxl_domain.c

@@ -362,16 +362,21 @@ libxlDomainDeviceDefPostParse(virDomainDeviceDefPtr dev,
         }
     }
 
-    /* for network-based disks, set 'qemu' as the default driver */
     if (dev->type == VIR_DOMAIN_DEVICE_DISK) {
         virDomainDiskDefPtr disk = dev->data.disk;
         int actual_type = virStorageSourceGetActualType(disk->src);
+        int format = virDomainDiskGetFormat(disk);
 
+        /* for network-based disks, set 'qemu' as the default driver */
         if (actual_type == VIR_STORAGE_TYPE_NETWORK) {
             if (!virDomainDiskGetDriver(disk) &&
                 virDomainDiskSetDriver(disk, "qemu") < 0)
                 return -1;
         }
+
+        /* xl.cfg default format is raw. See xl-disk-configuration(5) */
+        if (format == VIR_STORAGE_FILE_NONE)
+            virDomainDiskSetFormat(disk, VIR_STORAGE_FILE_RAW);
     }
 
     return 0;

src/libxl/libxl_driver.c

@@ -5468,8 +5468,7 @@ libxlDomainBlockStatsGatherSingle(virDomainObjPtr vm,
         disk_drv = "qemu";
 
     if (STREQ(disk_drv, "phy")) {
-        if (disk_fmt != VIR_STORAGE_FILE_RAW &&
-            disk_fmt != VIR_STORAGE_FILE_NONE) {
+        if (disk_fmt != VIR_STORAGE_FILE_RAW) {
             virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
                            _("unsupported format %s"),
                            virStorageFileFormatTypeToString(disk_fmt));