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

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Message-ID: <20170324105814.GC20282@gmail.com>
Date:   Fri, 24 Mar 2017 11:58:14 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
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>


* Kirill A. Shutemov <kirill@...temov.name> wrote:

> 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.

Good point - I'll keep it as-is unless convinced otherwise.

Thanks,

	Ingo