linux-kernel - Re: [RFC PATCH v2 01/10] lib: vdso: ensure all arches have 32bit fallback

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Message-Id: <53785EAC-A04C-4B02-9698-D11D75BE2C4D@amacapital.net>
Date:   Fri, 10 Jan 2020 11:02:38 -1000
From:   Andy Lutomirski <luto@...capital.net>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Arnd Bergmann <arnd@...db.de>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Andrew Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        X86 ML <x86@...nel.org>
Subject: Re: [RFC PATCH v2 01/10] lib: vdso: ensure all arches have 32bit fallback



> On Jan 10, 2020, at 10:56 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> Andy Lutomirski <luto@...nel.org> writes:
> 
>>> On Mon, Dec 23, 2019 at 6:31 AM Christophe Leroy
>>> <christophe.leroy@....fr> wrote:
>>> 
>>> In order to simplify next step which moves fallback call at arch
>>> level, ensure all arches have a 32bit fallback instead of handling
>>> the lack of 32bit fallback in the common code based
>>> on VDSO_HAS_32BIT_FALLBACK
>> 
>> I don't like this.  You've implemented what appear to be nonsensical
>> fallbacks (the 32-bit fallback for a 64-bit vDSO build?  There's no
>> such thing).
>> 
>> How exactly does this simplify patch 2?
> 
> There is a patchset from Vincenzo which fell through the cracks which
> addresses the VDS_HAS_32BIT_FALLBACK issue properly. I'm about to pick
> it up. See:
> 
> https://lore.kernel.org/lkml/20190830135902.20861-1-vincenzo.frascino@arm.com/
> 

Thanks.  I had been wondering why the conditionals were still there, since I remember seeing these patches.

> Thanks,
> 
>        tglx