linux-kernel - Re: [PATCH v2 00/33] locking/atomic: convert all architectures to ARCH

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAK8P3a2yH+dSWrS=1E0UbwcRhYJEThgrk2i9=omCQvcMMQZcww@mail.gmail.com>
Date:   Tue, 29 Jun 2021 09:36:23 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Brian Cain <bcain@...eaurora.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Chris Zankel <chris@...kel.net>, Rich Felker <dalias@...c.org>,
        David Miller <davem@...emloft.net>,
        Vincent Chen <deanbo422@...il.com>,
        Helge Deller <deller@....de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Greentime Hu <green.hu@...il.com>, Guo Ren <guoren@...nel.org>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Jonas Bonn <jonas@...thpole.se>,
        Ley Foon Tan <ley.foon.tan@...el.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Matt Turner <mattst88@...il.com>,
        Michal Simek <monstr@...str.eu>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nick Hu <nickhu@...estech.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Paul Mackerras <paulus@...ba.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Richard Henderson <rth@...ddle.net>,
        Stafford Horne <shorne@...il.com>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Vineet Gupta <vgupta@...opsys.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>
Subject: Re: [PATCH v2 00/33] locking/atomic: convert all architectures to ARCH_ATOMIC

On Tue, Jun 29, 2021 at 12:21 AM Randy Dunlap <rdunlap@...radead.org> wrote:
> On 6/28/21 3:13 PM, Peter Zijlstra wrote:
> > On Mon, Jun 28, 2021 at 02:22:15PM -0700, Randy Dunlap wrote:
> >
> > 0day also reported something like that. We found that this was a
> > pre-existing error, and Mark's patches only changed the error, it never
> > successfully build.
> >
> > cmpxchg64 is an optional feature for 32bit architectures, one that ARMv7
> > does provide, and uses, for it's iommu bits. Building the ARM iommu
> > drivers on ARC seem somewhat daft but is a result of that COMPILE_TEST
> > config.
> >
>
> Yes, I realize it's just a COMPILE_TEST config. Not very interesting IMHO.

Agreed as well. However, there is an interesting question in who gets to decide
which compile-test configurations are relevant and which ones are not.

I'm definitely interested in seeing any compile-time regression on the
architectures
I most care about (arm, arm64, x86) and I can see the same thing making
sense for other architectures that have someone chasing randconfig regressions,
but less so on architectures that fail general randconfig builds already.

For the specific case of cmpxchg64(), I do think it would make sense to either
have a Kconfig symbol that controls the few users, or to provide a spinlock
based fallback for those that don't have a native implementation.

        Arnd