2005-04-16 22:20:36 +00:00
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<previous description obsolete, deleted>
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Virtual memory map with 4 level page tables:
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0000000000000000 - 00007fffffffffff (=47bits) user space, different per mm
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hole caused by [48:63] sign extension
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ffff800000000000 - ffff80ffffffffff (=40bits) guard hole
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2005-11-05 16:25:54 +00:00
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ffff810000000000 - ffffc0ffffffffff (=46bits) direct mapping of all phys. memory
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2005-04-16 22:20:36 +00:00
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ffffc10000000000 - ffffc1ffffffffff (=40bits) hole
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ffffc20000000000 - ffffe1ffffffffff (=45bits) vmalloc/ioremap space
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... unused hole ...
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ffffffff80000000 - ffffffff82800000 (=40MB) kernel text mapping, from phys 0
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... unused hole ...
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ffffffff88000000 - fffffffffff00000 (=1919MB) module mapping space
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2005-11-05 16:25:54 +00:00
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The direct mapping covers all memory in the system upto the highest
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memory address (this means in some cases it can also include PCI memory
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holes)
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2005-04-16 22:20:36 +00:00
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vmalloc space is lazily synchronized into the different PML4 pages of
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the processes using the page fault handler, with init_level4_pgt as
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reference.
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Current X86-64 implementations only support 40 bit of address space,
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but we support upto 46bits. This expands into MBZ space in the page tables.
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-Andi Kleen, Jul 2004
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