Documentation/x86/x86_64/mm.txt

   1
   2 <previous description obsolete, deleted>
   3
   4 Virtual memory map with 4 level page tables:
   5
   6 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm
   7 hole caused by [48:63] sign extension
   8 ffff800000000000 - ffff80ffffffffff (=40 bits) guard hole
   9 ffff880000000000 - ffffc7ffffffffff (=64 TB) direct mapping of all phys. memory
  10 ffffc80000000000 - ffffc8ffffffffff (=40 bits) hole
  11 ffffc90000000000 - ffffe8ffffffffff (=45 bits) vmalloc/ioremap space
  12 ffffe90000000000 - ffffe9ffffffffff (=40 bits) hole
  13 ffffea0000000000 - ffffeaffffffffff (=40 bits) virtual memory map (1TB)
  14 ... unused hole ...
  15 ffffffff80000000 - ffffffffa0000000 (=512 MB)  kernel text mapping, from phys 0
  16 ffffffffa0000000 - ffffffffff5fffff (=1525 MB) module mapping space
  17 ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls
  18 ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole
  19
  20 The direct mapping covers all memory in the system up to the highest
  21 memory address (this means in some cases it can also include PCI memory
  22 holes).
  23
  24 vmalloc space is lazily synchronized into the different PML4 pages of
  25 the processes using the page fault handler, with init_level4_pgt as
  26 reference.
  27
  28 Current X86-64 implementations only support 40 bits of address space,
  29 but we support up to 46 bits. This expands into MBZ space in the page tables.
  30
  31 ->trampoline_pgd:
  32
  33 We map EFI runtime services in the aforementioned PGD in the virtual
  34 range of 64Gb (arbitrarily set, can be raised if needed)
  35
  36 0xffffffef00000000 - 0xffffffff00000000
  37
  38 -Andi Kleen, Jul 2004