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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B4B5C433FE for ; Tue, 21 Dec 2021 16:21:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239687AbhLUQVQ (ORCPT ); Tue, 21 Dec 2021 11:21:16 -0500 Received: from frasgout.his.huawei.com ([185.176.79.56]:4316 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236213AbhLUQVO (ORCPT ); Tue, 21 Dec 2021 11:21:14 -0500 Received: from fraeml705-chm.china.huawei.com (unknown [172.18.147.226]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4JJM602BDQz67M3D; Wed, 22 Dec 2021 00:16:40 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml705-chm.china.huawei.com (10.206.15.54) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.20; Tue, 21 Dec 2021 17:21:12 +0100 Received: from [10.195.32.222] (10.195.32.222) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Tue, 21 Dec 2021 16:21:11 +0000 From: John Garry Subject: Re: [GIT PULL 1/2] asm-generic: rework PCI I/O space access To: David Laight , Niklas Schnelle , Arnd Bergmann CC: Linus Torvalds , linux-arch , linux-pci , "Linux Kernel Mailing List" References: <5e8dfbd2-a6c0-6d02-53e9-1f29aebcc44e@huawei.com> <47744c7bce7b7bb37edee7f249d61dc57ac1fbc5.camel@linux.ibm.com> <849d70bddde1cfcb3ab1163970a148ff447ee94b.camel@linux.ibm.com> <53746e42-23a2-049d-9b38-dcfbaaae728f@huawei.com> <3a10b91258bf432baf51932a08335f6e@AcuMS.aculab.com> Message-ID: <192745f2-776b-f099-f428-c142b04d9a14@huawei.com> Date: Tue, 21 Dec 2021 16:21:10 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <3a10b91258bf432baf51932a08335f6e@AcuMS.aculab.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.195.32.222] X-ClientProxiedBy: lhreml750-chm.china.huawei.com (10.201.108.200) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/12/2021 14:23, David Laight wrote: >>>>> I have tested this on s390 with HAS_IOPORT=n and allyesconfig as well >>>>> as running it with defconfig. I've also been using it on my Ryzen 3990X >>>>> workstation with LEGACY_PCI=n for a few days. I do get about 60 MiB >>>>> fewer modules compared with a similar config of v5.15.8. Hard to say >>>>> which other systems might miss things of course. >>>>> >>>>> I have not yet worked on the discussed IOPORT_NATIVE flag. Mostly I'm >>>>> wondering two things. For one it feels like that could be a separate >>>>> change on top since HAS_IOPORT + LEGACY_PCI is already quite big. >>>>> Secondly I'm wondering about good ways of identifying such drivers and >>>>> how much this overlaps with the ISA config flag. >> I was interesting in the IOPORT_NATIVE flag (or whatever we call it) as >> it solves the problem of drivers which "unconditionally do inb()/outb() >> without checking the validity of the address using firmware or other >> methods first" being built for (and loaded on and crashing) unsuitable >> systems. Such a problem is in [0] >> >> So if we want to support that later, then it seems that someone would >> need to go back and re-edit many same driver Kconfigs – like hwmon, for >> example. I think it's better to avoid that and do it now. > Could you do something where valid arguments to inb() have to come > from some kernel mapping/validation function and are never in the > range [0x0, 0x10000). > Then drivers that are cheating the system will fail. That sounds like the solution which I had here: https://lore.kernel.org/lkml/1610729929-188490-2-git-send-email-john.garry@huawei.com/ It worked for the scenario I was interested in, but Arnd had some concerns, which you can check there. > > Or, maybe, only allow [0x0, 0x10000) on systems that have a suitable bus. > With the mapping functions returning a different value (eg the KVA into > the PCI master window) that can be separately verified. > That would let drivers do (say) inb(0x120) on systems that have (something > like) and ISA bus, but not on PCI-only systems which support PCI IO > accesses through a physical address window. I'm not sure how this would look in practice. What would the check for the suitable bus be? Thanks, John