Messages in this thread | | | Subject | Re: x86_64 virtual memory map | From | (Eric W. Biederman) | Date | Thu, 25 Mar 2010 21:34:02 -0700 |
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hayfeng Lee <omycle@gmail.com> writes:
> Hi,folks. > Recently I'm studying some things of x86_64 on Linux. And the virsion > is 2.6.18.8. From the document of Documentation/x86_64/mm.txt,I found > the mapping method for x86_64 virtual memory map. I want to know ,why > use this method for virtual memory mapping? > > ----------------------------------------------------------------------------------------------- > 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 > 9 ffff810000000000 - ffffc0ffffffffff (=46bits) direct mapping of > all phys. memory > 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 > 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 > 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 > > I urgently want to know the answer.
We can't give you the answer unless you give us the question, and enough context that the question makes sense. I recommend looking up the AMD and possibly the intel architecture documents on x86_64. They very completely cover what the processors can do and are freely available online.
Eric
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