Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   David Laight <David.Laight@ACULAB.COM>
To:     'Peter Zijlstra' <peterz@infradead.org>,
        Marco Elver <elver@google.com>
CC:     Will Deacon <will@kernel.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Dmitry Vyukov <dvyukov@google.com>
Subject: RE: [PATCH v5 00/18] Rework READ_ONCE() to improve codegen
Thread-Topic: [PATCH v5 00/18] Rework READ_ONCE() to improve codegen
Thread-Index: AQHWKfttZor7e2JWdEKPvqldyEhGwKipLI7w
Date:   Fri, 15 May 2020 13:55:43 +0000
Message-ID: <26283b5bccc8402cb8c243c569676dbd@AcuMS.aculab.com>
References: <20200513124021.GB20278@willie-the-truck>
 <CANpmjNM5XW+ufJ6Mw2Tn7aShRCZaUPGcH=u=4Sk5kqLKyf3v5A@mail.gmail.com>
 <20200513165008.GA24836@willie-the-truck>
 <CANpmjNN=n59ue06s0MfmRFvKX=WB2NgLgbP6kG_MYCGy2R6PHg@mail.gmail.com>
 <20200513174747.GB24836@willie-the-truck>
 <CANpmjNNOpJk0tprXKB_deiNAv_UmmORf1-2uajLhnLWQQ1hvoA@mail.gmail.com>
 <20200513212520.GC28594@willie-the-truck>
 <CANpmjNOAi2K6knC9OFUGjpMo-rvtLDzKMb==J=vTRkmaWctFaQ@mail.gmail.com>
 <20200514110537.GC4280@willie-the-truck>
 <CANpmjNMTsY_8241bS7=XAfqvZHFLrVEkv_uM4aDUWE_kh3Rvbw@mail.gmail.com>
 <20200514142450.GC2978@hirez.programming.kicks-ass.net>
In-Reply-To: <20200514142450.GC2978@hirez.programming.kicks-ass.net>
Accept-Language: en-GB, en-US
Content-Language: en-US
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8BIT
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Peter Zijlstra
> Sent: 14 May 2020 15:25
..
> Exact same requirements, KASAN even has the data_race() problem through
> READ_ONCE_NOCHECK(), UBSAN doesn't and might be simpler because of it.

What happens if you implement READ_ONCE_NOCHECK() with an
asm() statement containing a memory load?

Is that enough to kill all the instrumentation?

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)