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

[Kirill A. Shutemov]

On Sat, Dec 16, 2017 at 10:24:31PM +0100, Thomas Gleixner wrote:
> From: Andy Lutomirski <luto@xxxxxxxxxx>
> 
> 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@xxxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Brian Gerst <brgerst@xxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
> Cc: David Laight <David.Laight@xxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
> 
> ---
>  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