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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 882C2C5DF61 for ; Thu, 7 Nov 2019 10:28:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4A0C42087E for ; Thu, 7 Nov 2019 10:28:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387705AbfKGK2v (ORCPT ); Thu, 7 Nov 2019 05:28:51 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:14670 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726866AbfKGK2u (ORCPT ); Thu, 7 Nov 2019 05:28:50 -0500 Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id xA7ARuBv015631; Thu, 7 Nov 2019 11:27:56 +0100 Date: Thu, 7 Nov 2019 11:27:56 +0100 From: Willy Tarreau To: hpa@zytor.com Cc: Thomas Gleixner , Ingo Molnar , Linus Torvalds , LKML , the arch/x86 maintainers , Stephen Hemminger , Juergen Gross , Sean Christopherson Subject: Re: [patch 5/9] x86/ioport: Reduce ioperm impact for sane usage further Message-ID: <20191107102756.GD15536@1wt.eu> References: <20191106193459.581614484@linutronix.de> <20191106202806.241007755@linutronix.de> <20191107082541.GF30739@gmail.com> <20191107091704.GA15536@1wt.eu> <71DE81AC-3AD4-47B3-9CBA-A2C7841A3370@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <71DE81AC-3AD4-47B3-9CBA-A2C7841A3370@zytor.com> User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 07, 2019 at 02:19:19AM -0800, hpa@zytor.com wrote: > >Changing ioperm(single port, port range) to be ioperm(all) is going to > >break a bunch of test cases which actually check whether the permission > >is restricted to a single I/O port or the requested port range. > > > >Thanks, > > > > tglx > > This seems very undesirable... as much as we might wish otherwise, the port > bitmap is the equivalent to the MMU, and there are definitely users doing > direct device I/O out there. Doing these, sure, but doing these while ranges are really checked ? I mean, the MMU grants you access to the pages you were assigned. Here with the I/O bitmap you just have to ask for access to port X and you get it. I could understand the benefit if we had EBUSY in return but that's not the case, you can actually request access to a port range another device driver or process is currently using, and mess up with what it does even by accident. I remember streaming 1-bit music in userland from the LED of my floppy drive in the late-90s, it used to cause some trouble to the floppy driver when using mtools in parallel :-) Willy