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x86/mm: Update memory map description to list hypervisor-reserved area

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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>
This commit is contained in:
Dave Hansen 2014-09-18 12:56:06 -07:00 committed by Ingo Molnar
parent 8477957555
commit beb9147e95
1 changed files with 1 additions and 1 deletions
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2
Documentation/x86/x86_64/mm.txt
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@ -5,7 +5,7 @@ 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
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