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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 all 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
- The direct mapping covers all memory in the system upto the highest
- memory address (this means in some cases it can also include PCI memory
- holes)
- vmalloc space is lazily synchronized into the different PML4 pages of
- the processes using the page fault handler, with init_level4_pgt as
- reference.
- 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
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