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Peter Anvin says: > 0xffff880000000000 is the lowest usable address because we have > agreed to leave 0xffff800000000000-0xffff880000000000 for the > hypervisor or other non-OS uses. Let's call this out in the documentation. This came up during the kernel address sanitizer discussions where it was proposed to use this area for other kernel things. Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Link: http://lkml.kernel.org/r/20140918195606.841389D2@viggo.jf.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
41 lines
1.6 KiB
Plaintext
41 lines
1.6 KiB
Plaintext
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<previous description obsolete, deleted>
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Virtual memory map with 4 level page tables:
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0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm
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hole caused by [48:63] sign extension
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ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for hypervisor
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ffff880000000000 - ffffc7ffffffffff (=64 TB) direct mapping of all phys. memory
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ffffc80000000000 - ffffc8ffffffffff (=40 bits) hole
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ffffc90000000000 - ffffe8ffffffffff (=45 bits) vmalloc/ioremap space
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ffffe90000000000 - ffffe9ffffffffff (=40 bits) hole
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ffffea0000000000 - ffffeaffffffffff (=40 bits) virtual memory map (1TB)
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... unused hole ...
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ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks
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... unused hole ...
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ffffffff80000000 - ffffffffa0000000 (=512 MB) kernel text mapping, from phys 0
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ffffffffa0000000 - ffffffffff5fffff (=1525 MB) module mapping space
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ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls
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ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole
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The direct mapping covers all memory in the system up to the highest
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memory address (this means in some cases it can also include PCI memory
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holes).
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vmalloc space is lazily synchronized into the different PML4 pages of
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the processes using the page fault handler, with init_level4_pgt as
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reference.
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Current X86-64 implementations only support 40 bits of address space,
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but we support up to 46 bits. This expands into MBZ space in the page tables.
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->trampoline_pgd:
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We map EFI runtime services in the aforementioned PGD in the virtual
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range of 64Gb (arbitrarily set, can be raised if needed)
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0xffffffef00000000 - 0xffffffff00000000
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-Andi Kleen, Jul 2004
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