From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sat, 16 Apr 2005 15:20:36 -0700 Subject: Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip! --- Documentation/x86_64/mm.txt | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) create mode 100644 Documentation/x86_64/mm.txt (limited to 'Documentation/x86_64/mm.txt') diff --git a/Documentation/x86_64/mm.txt b/Documentation/x86_64/mm.txt new file mode 100644 index 000000000000..662b73971a67 --- /dev/null +++ b/Documentation/x86_64/mm.txt @@ -0,0 +1,24 @@ + + + +Virtual memory map with 4 level page tables: + +0000000000000000 - 00007fffffffffff (=47bits) user space, different per mm +hole caused by [48:63] sign extension +ffff800000000000 - ffff80ffffffffff (=40bits) guard hole +ffff810000000000 - ffffc0ffffffffff (=46bits) direct mapping of phys. memory +ffffc10000000000 - ffffc1ffffffffff (=40bits) hole +ffffc20000000000 - ffffe1ffffffffff (=45bits) vmalloc/ioremap space +... unused hole ... +ffffffff80000000 - ffffffff82800000 (=40MB) kernel text mapping, from phys 0 +... unused hole ... +ffffffff88000000 - fffffffffff00000 (=1919MB) module mapping space + +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 bit of address space, +but we support upto 46bits. This expands into MBZ space in the page tables. + +-Andi Kleen, Jul 2004 -- cgit v1.2.3