| 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 | |
| 6 | 0000000000000000 - 00007fffffffffff (=47bits) user space, different per mm |
| 7 | hole caused by [48:63] sign extension |
| 8 | ffff800000000000 - ffff80ffffffffff (=40bits) guard hole |
| Andi Kleen | 8315eca | 2005-11-05 17:25:54 +0100 | [diff] [blame^] | 9 | ffff810000000000 - ffffc0ffffffffff (=46bits) direct mapping of all phys. memory |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 10 | ffffc10000000000 - ffffc1ffffffffff (=40bits) hole |
| 11 | ffffc20000000000 - ffffe1ffffffffff (=45bits) vmalloc/ioremap space |
| 12 | ... unused hole ... |
| 13 | ffffffff80000000 - ffffffff82800000 (=40MB) kernel text mapping, from phys 0 |
| 14 | ... unused hole ... |
| 15 | ffffffff88000000 - fffffffffff00000 (=1919MB) module mapping space |
| 16 | |
| Andi Kleen | 8315eca | 2005-11-05 17:25:54 +0100 | [diff] [blame^] | 17 | The direct mapping covers all memory in the system upto the highest |
| 18 | memory address (this means in some cases it can also include PCI memory |
| 19 | holes) |
| 20 | |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 21 | vmalloc space is lazily synchronized into the different PML4 pages of |
| 22 | the processes using the page fault handler, with init_level4_pgt as |
| 23 | reference. |
| 24 | |
| 25 | Current X86-64 implementations only support 40 bit of address space, |
| 26 | but we support upto 46bits. This expands into MBZ space in the page tables. |
| 27 | |
| 28 | -Andi Kleen, Jul 2004 |