linux-kernel - Re: [patch RFC 00/15] mm/highmem: Provide a preemptible variant of kmap

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: <877dska7gw.fsf@nanos.tec.linutronix.de>
Date:   Wed, 23 Sep 2020 16:33:19 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Paul McKenney <paulmck@...nel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Will Deacon <will@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        Russell King <linux@...linux.org.uk>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        linux-xtensa@...ux-xtensa.org,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Vineet Gupta <vgupta@...opsys.com>,
        "open list\:SYNOPSYS ARC ARCHITECTURE" 
        <linux-snps-arc@...ts.infradead.org>,
        Arnd Bergmann <arnd@...db.de>, Guo Ren <guoren@...nel.org>,
        linux-csky@...r.kernel.org, Michal Simek <monstr@...str.eu>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org, Nick Hu <nickhu@...estech.com>,
        Greentime Hu <green.hu@...il.com>,
        Vincent Chen <deanbo422@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-sparc <sparclinux@...r.kernel.org>
Subject: Re: [patch RFC 00/15] mm/highmem: Provide a preemptible variant of kmap_atomic & friends

On Mon, Sep 21 2020 at 21:27, Thomas Gleixner wrote:
> On Mon, Sep 21 2020 at 09:24, Linus Torvalds wrote:
>> On Mon, Sep 21, 2020 at 12:39 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>> Maybe we really *could* call this new kmap functionality something
>> like "kmap_percpu()" (or maybe "local" is good enough), and make it
>> act like your RT code does for spinlocks - not disable preemption, but
>> only disabling CPU migration.
>
> I"m all for it, but the scheduler people have opinions :)

I just took the latest version of migrate disable patches

  https://lore.kernel.org/r/20200921163557.234036895@infradead.org

removed the RT dependency on top of them and adopted the kmap stuff
(addressing the various comments while at it and unbreaking ARM).

I'm not going to post that until there is consensus about the general
availability of migrate disable, but for those who want to play with it
I've pushed the resulting combo out to:

   git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git highmem 

For testing I've tweaked a few places to use the new _local() variants
and it survived testing so far and I've verified that there is actual
preemption which means zap/restore of the thread local kmaps.

Thanks,

        tglx