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Diffstat (limited to 'kernel/Documentation/x86/x86_64/mm.txt')
| -rw-r--r-- | kernel/Documentation/x86/x86_64/mm.txt | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/kernel/Documentation/x86/x86_64/mm.txt b/kernel/Documentation/x86/x86_64/mm.txt new file mode 100644 index 000000000..05712ac83 --- /dev/null +++ b/kernel/Documentation/x86/x86_64/mm.txt @@ -0,0 +1,42 @@ + +<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 |