From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27F4DC43465 for ; Sun, 20 Sep 2020 20:49:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5109B20758 for ; Sun, 20 Sep 2020 20:49:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5109B20758 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arndb.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 7222F6B0093; Sun, 20 Sep 2020 16:49:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6D273900009; 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Sun, 20 Sep 2020 20:49:23 +0000 (UTC) Received: from mail-qt1-f179.google.com ([209.85.160.179]) by mrelayeu.kundenserver.de (mreue010 [212.227.15.129]) with ESMTPSA (Nemesis) id 1Mj8a5-1kwCyS44m5-00fAoK; Sun, 20 Sep 2020 22:49:22 +0200 Received: by mail-qt1-f179.google.com with SMTP id e7so10556505qtj.11; Sun, 20 Sep 2020 13:49:21 -0700 (PDT) X-Gm-Message-State: AOAM530Pt3ysCmIWvvcpDsH/zIgRLmjh8wgnoYENWmd2NKM5aPfxzPCq w6Cuw2UmBWc9RyCb91UF3QZzpkWbjASgHdmxLOk= X-Google-Smtp-Source: ABdhPJwBXwBil3iRHV11f3BxYsgRD++l69TenwTYSqKgYe+2Dux9TFUrSKvqlq1FFlXpzrttVMSzDz47tEK6RfJnMjg= X-Received: by 2002:aed:2ce5:: with SMTP id g92mr30020804qtd.204.1600634960428; Sun, 20 Sep 2020 13:49:20 -0700 (PDT) MIME-Version: 1.0 References: <20200918124533.3487701-1-hch@lst.de> <20200918124533.3487701-2-hch@lst.de> <20200920151510.GS32101@casper.infradead.org> <20200920180742.GN3421308@ZenIV.linux.org.uk> <20200920190159.GT32101@casper.infradead.org> <20200920191031.GQ3421308@ZenIV.linux.org.uk> <20200920192259.GU32101@casper.infradead.org> In-Reply-To: From: Arnd Bergmann Date: Sun, 20 Sep 2020 22:49:03 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag To: Andy Lutomirski Cc: Matthew Wilcox , Al Viro , Christoph Hellwig , Andrew Morton , Jens Axboe , David Howells , linux-arm-kernel , X86 ML , LKML , "open list:MIPS" , Parisc List , linuxppc-dev , linux-s390 , sparclinux , linux-block , Linux SCSI List , Linux FS Devel , linux-aio , io-uring@vger.kernel.org, linux-arch , Linux-MM , Network Development , keyrings@vger.kernel.org, LSM List Content-Type: text/plain; charset="UTF-8" X-Provags-ID: V03:K1:dDM6e9irZhkOMLh8TV6WKKM8Y0fRsy4VQpijl6wFnE2hu+QQWAj oAS/BV1T6PGRzmQwRfyv8IXaqqh/GNwpVPjpMkud1u94ubIWMP7xWCGaE+16KansyrGT0eS 4mNN7O+IialjVwx+kOIjdaKMaaP5Pvck1N+GFc+VSuabUy1wQPqSWSIHaBMQ0jwKwfpLjGk tLI/vH7NkFy5aHYsqnytQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:uhtIU0Sa0jI=:8sOk5p0hNPBW9K97I/aPiH iOpe029l/Feiq2tD6QWipCAO3YGOHGEQPWxZHa+UgJIFiyOWyo60scdECRNeI2BLwKWpLObix sniwyrbXTEIGfrJK7ASO1xn3LTi94sSWr5HmubCKoo3PzNB5pkHDJQh4czoE5qmxq/W3bFRUn KYi64NhrD1zXzepr+8xNlczHbaZZwschAL9Ja1sKH8Elim5D1Ofd0whE85DdYKvQhqBkeNWCX LRhehyqDlxFpxt218h4qJHIZ0IhJejKaIbCx9S/3ihZ3dDYM9+9+P43jiTwRmIbbr2fcAZ3KX WE0i78OOesPCgRi1law5TT0amiVJKwMOpwk9OwOZjruvkEnSI/eOktD0iZbDdyCDjcLvoGHHL /IIsl8OK62aR9lD7EynN6aPHAOneKLxZ4hhUNRMMJD7sMsA5VB+2FlEoISQMZe0OSmFOWdsbT OcIkh+cN1KCPwzQKwyVMAcpN/4KajW1RNTedzyigVuZaBHnyQudCebGBBktRCn4irDXdElFsh YSJZa8FnE/KdKT/W/T4PZoS1H+2B8cHf5QPVsMN3n0Ey1CRfYOBev4KBbqKfFsSinTsoB5Dpw 7B0xt+3ru/zuL4Yj+xjNI/BOEiU26ddgkre7Gm4fkH64SuwaB78HWdyyjcTq2HbSt2aC82Gy8 W7R7J2sMlav4TeSnbY1c6ACB7Dc0PSC0Xg3MOACoJgmR+VZPcVVAHI6EiXTQbwSIo6VPASu/K xCk6OH9Z1sg0Yil0AJ/bW9hIcAlRAnRZhWmA13CrM5K/qZWD+/05dMT4RmXBHkD5QjonPpvGu zlenn3nqcwBaVg/ETdLS6/U1pB+FZVj5ba5yBkH//w6sb8/eModF4UoJmBthufMiyNvRHSR X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, Sep 20, 2020 at 9:28 PM Andy Lutomirski wrote: > On Sun, Sep 20, 2020 at 12:23 PM Matthew Wilcox wrote: > > > > On Sun, Sep 20, 2020 at 08:10:31PM +0100, Al Viro wrote: > > > IMO it's much saner to mark those and refuse to touch them from io_uring... > > > > Simpler solution is to remove io_uring from the 32-bit syscall list. > > If you're a 32-bit process, you don't get to use io_uring. Would > > any real users actually care about that? > > We could go one step farther and declare that we're done adding *any* > new compat syscalls :) Would you also stop adding system calls to native 32-bit systems then? On memory constrained systems (less than 2GB a.t.m.), there is still a strong demand for running 32-bit user space, but all of the recent Arm cores (after Cortex-A55) dropped the ability to run 32-bit kernels, so that compat mode may eventually become the primary way to run Linux on cheap embedded systems. I don't think there is any chance we can realistically take away io_uring from the 32-bit ABI any more now. Arnd