>We just expect tboot to be used together with VMM/Kernel with tboot support.
>The tboot support should be confirmed before adding tboot to the control
>flow. So we don't add any interface in Xen/Linux to indicate the tboot
>support to tboot in the runtime.
  I see what you are conveying. So, it is possible for tboot to boot a hypervisor (bitvisor), even though bitvisor does not support tboot. Nevertheless, bitvisor still can not be booted by tboot. I also checked the log that tboot produces when tboot is being loaded. The system always reboots after the log prints out: no LCP module found, kernel is elf format. According to the tboot spec, the log is expected to continue printing: transfering control to ...@0x... But it does not and system begins to reboot. 
 I wonder if the menuentry of tboot is configured right.
  menuentry 'Tboot, with Linux 3.2.2' --class ubuntu --class gnu-linux --class gnu --class os {
        insmod ext2
        set root='(hd0,6)'
        search --no-floppy --fs-uuid --set b99ce3bb-2938-44e9-8277-cc5c8f942e81
        multiboot  /boot/tboot.gz tboot.gz logging=serial,vga,memory
        module  /boot/bitvisor.elf bitvisor.elf
        module  /boot/vmlinuz-3.2.2 vmlinuz-3.2.2 root=UUID=b99ce3bb-2938-44e9-8277-cc5c8f942e81 ro rootdelay=120
        #multiboot  /boot/bitvisor.elf bitvisor.elf
        #module (hd0)+6
        module  /boot/initrd.img-3.2.2 initrd.img-3.2.2
        module  /boot/2nd_gen_i5_i7_SINIT_51.BIN 2nd_gen_i5_i7_SINIT_51.BIN
        #module  /boot/list.data list.data