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+<previous description obsolete, deleted>
+Virtual memory map with 4 level page tables:
+0000000000000000 - 00007fffffffffff (=47bits) user space, different per mm
+hole caused by [48:63] sign extension
+ffff800000000000 - ffff80ffffffffff (=40bits) guard hole
+ffff810000000000 - ffffc0ffffffffff (=46bits) direct mapping of phys. memory
+ffffc10000000000 - ffffc1ffffffffff (=40bits) hole
+ffffc20000000000 - ffffe1ffffffffff (=45bits) vmalloc/ioremap space
+... unused hole ...
+ffffffff80000000 - ffffffff82800000 (=40MB) kernel text mapping, from phys 0
+... unused hole ...
+ffffffff88000000 - fffffffffff00000 (=1919MB) module mapping space
+vmalloc space is lazily synchronized into the different PML4 pages of
+the processes using the page fault handler, with init_level4_pgt as
+Current X86-64 implementations only support 40 bit of address space,
+but we support upto 46bits. This expands into MBZ space in the page tables.
+-Andi Kleen, Jul 2004