Re: [PATCH 4/6] x86/kasan: Prepare clear_pgds() to switch to <asm-generic/pgtable-nop4d.h>

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To: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Subject: Re: [PATCH 4/6] x86/kasan: Prepare clear_pgds() to switch to <asm-generic/pgtable-nop4d.h>
From: Ingo Molnar <mingo@xxxxxxxxxx>
Date: Wed, 22 Mar 2017 08:31:36 +0100
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, x86@xxxxxxxxxx, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Andi Kleen <ak@xxxxxxxxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxxxxxx>, Michal Hocko <mhocko@xxxxxxxx>, linux-arch@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Dmitry Vyukov <dvyukov@xxxxxxxxxx>
In-reply-to: <218853b4-3498-dab9-d1e9-02caed4d9322@virtuozzo.com>
References: <20170317185515.8636-1-kirill.shutemov@linux.intel.com> <20170317185515.8636-5-kirill.shutemov@linux.intel.com> <218853b4-3498-dab9-d1e9-02caed4d9322@virtuozzo.com>
User-agent: Mutt/1.5.24 (2015-08-30)

* Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> wrote:

> 
> 
> On 03/17/2017 09:55 PM, Kirill A. Shutemov wrote:
> > With folded p4d, pgd_clear() is nop. Change clear_pgds() to use
> > p4d_clear() instead.
> > 
> 
> You could probably just use set_pgd(pgd_offset_k(start), __pgd(0)); instead of pgd_clear()
> as we already do in arm64.
> It's basically pgd_clear() except it's not a nop wih p4d folded.

Makes sense. Kirill, if you agree, mind spinning a v2 patch?

Thanks,

	Ingo

Follow-Ups:
- Re: [PATCH 4/6] x86/kasan: Prepare clear_pgds() to switch to <asm-generic/pgtable-nop4d.h>
  - From: Kirill A. Shutemov

References:
- [PATCH 0/6] x86: 5-level paging enabling for v4.12, Part 2
  - From: Kirill A. Shutemov
- [PATCH 4/6] x86/kasan: Prepare clear_pgds() to switch to <asm-generic/pgtable-nop4d.h>
  - From: Kirill A. Shutemov
- Re: [PATCH 4/6] x86/kasan: Prepare clear_pgds() to switch to <asm-generic/pgtable-nop4d.h>
  - From: Andrey Ryabinin

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