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 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 B518FC433DB for ; Sat, 19 Sep 2020 23:24:25 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 02AAC222BB for ; Sat, 19 Sep 2020 23:24:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 02AAC222BB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0C9476B0037; Sat, 19 Sep 2020 19:24:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F40176B005A; Sat, 19 Sep 2020 19:24:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E07476B005D; Sat, 19 Sep 2020 19:24:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0243.hostedemail.com [216.40.44.243]) by kanga.kvack.org (Postfix) with ESMTP id BD1676B0055 for ; Sat, 19 Sep 2020 19:24:22 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 824CC1EFF for ; Sat, 19 Sep 2020 23:24:22 +0000 (UTC) X-FDA: 77281391964.01.hall51_34103ac27137 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin01.hostedemail.com (Postfix) with ESMTP id 517EC10047E35; Sat, 19 Sep 2020 23:24:22 +0000 (UTC) X-HE-Tag: hall51_34103ac27137 X-Filterd-Recvd-Size: 2123 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [195.92.253.2]) by imf29.hostedemail.com (Postfix) with ESMTP; Sat, 19 Sep 2020 23:24:21 +0000 (UTC) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kJmDD-0020kM-6N; Sat, 19 Sep 2020 23:24:11 +0000 Date: Sun, 20 Sep 2020 00:24:11 +0100 From: Al Viro To: Andy Lutomirski Cc: Christoph Hellwig , Andrew Morton , Jens Axboe , Arnd Bergmann , David Howells , linux-arm-kernel@lists.infradead.org, x86@kernel.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, io-uring@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Message-ID: <20200919232411.GK3421308@ZenIV.linux.org.uk> References: <20200919224122.GJ3421308@ZenIV.linux.org.uk> <36CF3DE7-7B4B-41FD-9818-FDF8A5B440FB@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <36CF3DE7-7B4B-41FD-9818-FDF8A5B440FB@amacapital.net> Content-Transfer-Encoding: quoted-printable 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 Sat, Sep 19, 2020 at 03:53:40PM -0700, Andy Lutomirski wrote: > > It would not be a win - most of the syscalls don't give a damn > > about 32bit vs. 64bit... >=20 > Any reasonable implementation would optimize it out for syscalls that d= on=E2=80=99t care. Or it could be explicit: >=20 > DEFINE_MULTIARCH_SYSCALL(...) 1) what would that look like? 2) have you counted the syscalls that do and do not need that? 3) how many of those realistically *can* be unified with their compat counterparts? [hint: ioctl(2) cannot]