Comment # 7 on bug 989284 from Jan Kara

Current version of grub2 definitely supports 64-bit feature. So I guess it has
to be the first... But I don't understand the details how grub2 and u-boot
interact...

Andreas, Alex is it feasible to add 64-bit feature support to u-boot? For a
bootloader support of 64-bit feature is usually pretty trivial - it only
changes XATTR block number in an inode from 32 to 48 bits (but bootloader
usually doesn't care about this since it ignores xattrs anyway) and it changes
block numbers of inode and block bitmaps in the group descriptor from 32 to 48
bits (but again bootloader generally doesn't even parse group descriptors).