linux-kernel - Re: [patch V149 37/50] x86/mm/64: Make a full PGD-entry size hole in the memory map

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Date:   Sun, 17 Dec 2017 14:07:25 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirsky <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Borislav Petkov <bpetkov@...e.de>,
        Greg KH <gregkh@...uxfoundation.org>, keescook@...gle.com,
        hughd@...gle.com, Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Rik van Riel <riel@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        David Laight <David.Laight@...lab.com>,
        Eduardo Valentin <eduval@...zon.com>, aliguori@...zon.com,
        Will Deacon <will.deacon@....com>, daniel.gruss@...k.tugraz.at,
        Kees Cook <keescook@...omium.org>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [patch V149 37/50] x86/mm/64: Make a full PGD-entry size hole in
 the memory map

On Sat, Dec 16, 2017 at 10:24:31PM +0100, Thomas Gleixner wrote:
> From: Andy Lutomirski <luto@...nel.org>
> 
> Shrink vmalloc space from 16384TiB to 12800TiB to enlarge the hole starting
> at 0xff90000000000000 to be a full PGD entry.
> 
> A subsequent patch will use this hole for the pagetable isolation LDT
> alias.
> 
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Brian Gerst <brgerst@...il.com>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: David Laight <David.Laight@...lab.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: "Kirill A. Shutemov" <kirill@...temov.name>
> 
> ---
>  Documentation/x86/x86_64/mm.txt         | 4 ++--
>  arch/x86/include/asm/pgtable_64_types.h | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/x86/x86_64/mm.txt b/Documentation/x86/x86_64/mm.txt
> index 63a41671d25b..6a28aeaccd53 100644
> --- a/Documentation/x86/x86_64/mm.txt
> +++ b/Documentation/x86/x86_64/mm.txt
> @@ -28,8 +28,8 @@ Virtual memory map with 5 level page tables:
>  hole caused by [56:63] sign extension
>  ff00000000000000 - ff0fffffffffffff (=52 bits) guard hole, reserved for hypervisor
>  ff10000000000000 - ff8fffffffffffff (=55 bits) direct mapping of all phys. memory
> -ff90000000000000 - ff91ffffffffffff (=49 bits) hole
> -ff92000000000000 - ffd1ffffffffffff (=54 bits) vmalloc/ioremap space
> +ff90000000000000 - ff9fffffffffffff (=52 bits) hole
> +ffa0000000000000 - ffd1ffffffffffff (=54 bits) vmalloc/ioremap space

  +ffa0000000000000 - ffd1ffffffffffff (=12800 TB) vmalloc/ioremap space

-- 
 Kirill A. Shutemov