linux-kernel - Re: [PATCH PTI v3 09/10] x86/mm/64: Make a full PGD-entry size hole in the memory map

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Date:   Wed, 13 Dec 2017 09:04:51 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH PTI v3 09/10] x86/mm/64: Make a full PGD-entry size hole
 in the memory map

Whoops.  I'll change that to "(=12800 TB)".

On Wed, Dec 13, 2017 at 5:17 AM, Kirill A. Shutemov
<kirill@...temov.name> wrote:
> On Tue, Dec 12, 2017 at 07:56:44AM -0800, Andy Lutomirski wrote:
>> This patch shrinks 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.
>>
>> Cc: "Kirill A. Shutemov" <kirill@...temov.name>
>> Cc: Dave Hansen <dave.hansen@...el.com>
>> Signed-off-by: Andy Lutomirski <luto@...nel.org>
>> ---
>>  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
>
> It's not 54 bits anymore.
>
> --
>  Kirill A. Shutemov