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

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Date:   Fri, 24 Mar 2017 12:07:57 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Andy Lutomirski <luto@...capital.net>,
        Michal Hocko <mhocko@...e.com>, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH 4/6] x86/kasan: Prepare clear_pgds() to switch to
 <asm-generic/pgtable-nop4d.h>

On Wed, Mar 22, 2017 at 08:31:36AM +0100, Ingo Molnar wrote:
> * Andrey Ryabinin <aryabinin@...tuozzo.com> 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?

I can re-spin, if you want. But honestly, I don't think such constructs
help readability.

-- 
 Kirill A. Shutemov