builder/qemu: specify disk format to avoid errors

Image format was not specified for XXX and probing
guessed raw.
Automatically detecting the format is dangerous for raw images, write
operations on block 0 will be restricted.
Specify the 'raw' format explicitly to remove the restrictions.

Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>

builder/qemu/step_run.go

@@ -91,12 +91,12 @@ func getCommandArgs(bootDrive string, state multistep.StateBag) ([]string, error
 	if qemuMajor >= 2 {
 		if config.DiskInterface == "virtio-scsi" {
 			deviceArgs = append(deviceArgs, "virtio-scsi-pci,id=scsi0", "scsi-hd,bus=scsi0.0,drive=drive0")
-			driveArgs = append(driveArgs, fmt.Sprintf("if=none,file=%s,id=drive0,cache=%s,discard=%s", imgPath, config.DiskCache, config.DiskDiscard))
+			driveArgs = append(driveArgs, fmt.Sprintf("if=none,file=%s,id=drive0,cache=%s,discard=%s,format=%s", imgPath, config.DiskCache, config.DiskDiscard, config.Format))
 		} else {
-			driveArgs = append(driveArgs, fmt.Sprintf("file=%s,if=%s,cache=%s,discard=%s", imgPath, config.DiskInterface, config.DiskCache, config.DiskDiscard))
+			driveArgs = append(driveArgs, fmt.Sprintf("file=%s,if=%s,cache=%s,discard=%s,format=%s", imgPath, config.DiskInterface, config.DiskCache, config.DiskDiscard, config.Format))
 		}
 	} else {
-		driveArgs = append(driveArgs, fmt.Sprintf("file=%s,if=%s,cache=%s", imgPath, config.DiskInterface, config.DiskCache))
+		driveArgs = append(driveArgs, fmt.Sprintf("file=%s,if=%s,cache=%s,format=%s", imgPath, config.DiskInterface, config.DiskCache, config.Format))
 	}
 	deviceArgs = append(deviceArgs, fmt.Sprintf("%s,netdev=user.0", config.NetDevice))