ffff810000000000 - ffffc0ffffffffff (=46 bits) direct mapping of all phys. memory
ffffc10000000000 - ffffc1ffffffffff (=40 bits) hole
ffffc20000000000 - ffffe1ffffffffff (=45 bits) vmalloc/ioremap space
ffff810000000000 - ffffc0ffffffffff (=46 bits) direct mapping of all phys. memory
ffffc10000000000 - ffffc1ffffffffff (=40 bits) hole
ffffc20000000000 - ffffe1ffffffffff (=45 bits) vmalloc/ioremap space