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kernel/linux-rt-4.4.41/Documentation/x86/x86_64/mm.txt 1.69 KB
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  <previous description obsolete, deleted>
  
  Virtual memory map with 4 level page tables:
  
  0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm
  hole caused by [48:63] sign extension
  ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for hypervisor
  ffff880000000000 - ffffc7ffffffffff (=64 TB) direct mapping of all phys. memory
  ffffc80000000000 - ffffc8ffffffffff (=40 bits) hole
  ffffc90000000000 - ffffe8ffffffffff (=45 bits) vmalloc/ioremap space
  ffffe90000000000 - ffffe9ffffffffff (=40 bits) hole
  ffffea0000000000 - ffffeaffffffffff (=40 bits) virtual memory map (1TB)
  ... unused hole ...
  ffffec0000000000 - fffffc0000000000 (=44 bits) kasan shadow memory (16TB)
  ... unused hole ...
  ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks
  ... unused hole ...
  ffffffff80000000 - ffffffffa0000000 (=512 MB)  kernel text mapping, from phys 0
  ffffffffa0000000 - ffffffffff5fffff (=1525 MB) module mapping space
  ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls
  ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole
  
  The direct mapping covers all memory in the system up to 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 bits of address space,
  but we support up to 46 bits. This expands into MBZ space in the page tables.
  
  ->trampoline_pgd:
  
  We map EFI runtime services in the aforementioned PGD in the virtual
  range of 64Gb (arbitrarily set, can be raised if needed)
  
  0xffffffef00000000 - 0xffffffff00000000
  
  -Andi Kleen, Jul 2004