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

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Message-ID: <CAPAsAGzSfW6ba5Bcij_ndVZ7M8fyQGWS7KO76NZDbifRbW-XNg@mail.gmail.com>
Date:	Thu, 18 Sep 2014 20:42:10 +0400
From:	Andrey Ryabinin <ryabinin.a.a@...il.com>
To:	Dave Hansen <dave@...1.net>
Cc:	LKML <linux-kernel@...r.kernel.org>, dave.hansen@...ux.intel.com,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] x86: update memory map about hypervisor-reserved area

2014-09-18 19:46 GMT+04:00 Dave Hansen <dave@...1.net>:
>
> From: Dave Hansen <dave.hansen@...ux.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@...ux.intel.com>
> Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>
> Cc: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Andi Kleen <andi@...stfloor.org>
> Cc: x86@...nel.org
> Cc: linux-mm@...ck.org
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.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
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