[linux-2.6-block.git] / Documentation / x86_64 / mm.txt


<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 - ffff80ffffffffff (=40 bits) guard hole
ffff810000000000 - ffffc0ffffffffff (=46 bits) direct mapping of all phys. memory
ffffc10000000000 - ffffc1ffffffffff (=40 bits) hole
ffffc20000000000 - ffffe1ffffffffff (=45 bits) vmalloc/ioremap space
ffffe20000000000 - ffffe2ffffffffff (=40 bits) virtual memory map (1TB)
... unused hole ...
ffffffff80000000 - ffffffffa0000000 (=512 MB)  kernel text mapping, from phys 0
ffffffffa0000000 - fffffffffff00000 (=1536 MB) module mapping space

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.

-Andi Kleen, Jul 2004
Commit	Line	Data
1da177e4 LT	1
	2	<previous description obsolete, deleted>
	3
	4	Virtual memory map with 4 level page tables:
	5
57d30772	6	0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm
1da177e4	7	hole caused by [48:63] sign extension
57d30772 RD	8	ffff800000000000 - ffff80ffffffffff (=40 bits) guard hole
	9	ffff810000000000 - ffffc0ffffffffff (=46 bits) direct mapping of all phys. memory
	10	ffffc10000000000 - ffffc1ffffffffff (=40 bits) hole
	11	ffffc20000000000 - ffffe1ffffffffff (=45 bits) vmalloc/ioremap space
0889eba5	12	ffffe20000000000 - ffffe2ffffffffff (=40 bits) virtual memory map (1TB)
1da177e4	13	... unused hole ...
cca7c085 JS	14	ffffffff80000000 - ffffffffa0000000 (=512 MB) kernel text mapping, from phys 0
cca7c085 JS	15	ffffffffa0000000 - fffffffffff00000 (=1536 MB) module mapping space
1da177e4	16
57d30772	17	The direct mapping covers all memory in the system up to the highest
8315eca2	18	memory address (this means in some cases it can also include PCI memory
57d30772	19	holes).
8315eca2	20
1da177e4 LT	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
57d30772 RD	25	Current X86-64 implementations only support 40 bits of address space,
57d30772 RD	26	but we support up to 46 bits. This expands into MBZ space in the page tables.
1da177e4 LT	27
1da177e4 LT	28	-Andi Kleen, Jul 2004