| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | |
| 2 | <previous description obsolete, deleted> |
| 3 | |
| 4 | Virtual memory map with 4 level page tables: |
| 5 | |
| Randy Dunlap | 57d3077 | 2007-02-13 13:26:23 +0100 | [diff] [blame] | 6 | 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 7 | hole caused by [48:63] sign extension |
| Randy Dunlap | 57d3077 | 2007-02-13 13:26:23 +0100 | [diff] [blame] | 8 | ffff800000000000 - ffff80ffffffffff (=40 bits) guard hole |
| H. Peter Anvin | 2feceef | 2009-05-05 19:07:07 -0700 | [diff] [blame] | 9 | ffff880000000000 - ffffc7ffffffffff (=64 TB) direct mapping of all phys. memory |
| Rik van Riel | c898faf | 2009-05-05 17:28:56 -0400 | [diff] [blame] | 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) |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 14 | ... unused hole ... |
| Jiri Slaby | cca7c08 | 2008-05-12 15:43:37 +0200 | [diff] [blame] | 15 | ffffffff80000000 - ffffffffa0000000 (=512 MB) kernel text mapping, from phys 0 |
| 16 | ffffffffa0000000 - fffffffffff00000 (=1536 MB) module mapping space |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 17 | |
| Randy Dunlap | 57d3077 | 2007-02-13 13:26:23 +0100 | [diff] [blame] | 18 | The direct mapping covers all memory in the system up to the highest |
| Andi Kleen | 8315eca | 2005-11-05 17:25:54 +0100 | [diff] [blame] | 19 | memory address (this means in some cases it can also include PCI memory |
| Randy Dunlap | 57d3077 | 2007-02-13 13:26:23 +0100 | [diff] [blame] | 20 | holes). |
| Andi Kleen | 8315eca | 2005-11-05 17:25:54 +0100 | [diff] [blame] | 21 | |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 22 | vmalloc space is lazily synchronized into the different PML4 pages of |
| 23 | the processes using the page fault handler, with init_level4_pgt as |
| 24 | reference. |
| 25 | |
| Randy Dunlap | 57d3077 | 2007-02-13 13:26:23 +0100 | [diff] [blame] | 26 | Current X86-64 implementations only support 40 bits of address space, |
| 27 | but we support up to 46 bits. This expands into MBZ space in the page tables. |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 28 | |
| 29 | -Andi Kleen, Jul 2004 |