[PATCH] x86: update memory map about hypervisor-reserved area

[PATCH] x86: update memory map about hypervisor-reserved area

[Dave Hansen]

From: Dave Hansen <dave.hansen@linux.intel.com>

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>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: x86@kernel.org
Cc: linux-mm@kvack.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
---

 b/Documentation/x86/x86_64/mm.txt |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -puN Documentation/x86/x86_64/mm.txt~update-x86-mm-doc Documentation/x86/x86_64/mm.txt
--- a/Documentation/x86/x86_64/mm.txt~update-x86-mm-doc	2014-09-17 21:44:10.499781092 -0700
+++ b/Documentation/x86/x86_64/mm.txt	2014-09-17 21:44:31.852740822 -0700
@@ -5,7 +5,7 @@ Virtual memory map with 4 level page tab
 
 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm
 hole caused by [48:63] sign extension
-ffff800000000000 - ffff80ffffffffff (=40 bits) guard hole
+ffff800000000000 - ffff80ffffffffff (=40 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
_

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] x86: update memory map about hypervisor-reserved area

[Andrey Ryabinin]

2014-09-18 19:46 GMT+04:00 Dave Hansen <dave@sr71.net>:
>
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> 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>
> Cc: Andi Kleen <andi@firstfloor.org>
> Cc: x86@kernel.org
> Cc: linux-mm@kvack.org
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> ---
>
>  b/Documentation/x86/x86_64/mm.txt |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff -puN Documentation/x86/x86_64/mm.txt~update-x86-mm-doc Documentation/x86/x86_64/mm.txt
> --- a/Documentation/x86/x86_64/mm.txt~update-x86-mm-doc 2014-09-17 21:44:10.499781092 -0700
> +++ b/Documentation/x86/x86_64/mm.txt   2014-09-17 21:44:31.852740822 -0700
> @@ -5,7 +5,7 @@ Virtual memory map with 4 level page tab
>
>  0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm
>  hole caused by [48:63] sign extension
> -ffff800000000000 - ffff80ffffffffff (=40 bits) guard hole
> +ffff800000000000 - ffff80ffffffffff (=40 bits) guard hole, reserved for hypervisor

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
> _



-- 
Best regards,
Andrey Ryabinin

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>