From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757642AbYAJCaw (ORCPT ); Wed, 9 Jan 2008 21:30:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753333AbYAJCao (ORCPT ); Wed, 9 Jan 2008 21:30:44 -0500 Received: from waste.org ([66.93.16.53]:46033 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753037AbYAJCan (ORCPT ); Wed, 9 Jan 2008 21:30:43 -0500 Subject: Re: Replacement for page fault notifiers? From: Matt Mackall To: Pavel Roskin Cc: Arjan van de Ven , Christoph Hellwig , Benjamin Herrenschmidt , Dave Airlie , Pekka Paalanen , linux-kernel@vger.kernel.org, jbeulich@novell.com In-Reply-To: <1199931693.21499.11.camel@dv> References: <20080108210638.5c9e093a@daedalus.pq.iki.fi> <20080108203235.GA772@infradead.org> <21d7e9970801081413n307ab07aq462a9fff014143ae@mail.gmail.com> <1199838407.6734.83.camel@pasglop> <1199902724.8050.11.camel@dv> <20080109182157.GA32754@infradead.org> <1199908703.6734.133.camel@pasglop> <20080109202254.GA5279@infradead.org> <20080109164241.7daa5770@laptopd505.fenrus.org> <1199930590.6245.104.camel@cinder.waste.org> <1199931693.21499.11.camel@dv> Content-Type: text/plain Date: Wed, 09 Jan 2008 20:30:04 -0600 Message-Id: <1199932204.6245.110.camel@cinder.waste.org> Mime-Version: 1.0 X-Mailer: Evolution 2.12.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2008-01-09 at 21:21 -0500, Pavel Roskin wrote: > On Wed, 2008-01-09 at 20:03 -0600, Matt Mackall wrote: > > > That makes it way too easy for drivers of questionable legality to just > > clear that bit. Also, we've got a shortage of page bits, etc. > > If we ever have this problem, the bit can be changed in the kernel to > fool those drivers (I hope the shortage is not so dire that there will > be no more bits left). That's what we call an arms race. And yes, page bits are close to running out on 32-bit. > I don't think evil drivers should be a problem per se. There are > existing non-free drivers that still need to be traced over and over > again. I guess ndiswrapper could use tracing for Windows drivers that > don't know anything about Linux page flags. > > Last but not least, mmiotrace should be useful for free drivers in the > first place to have a legitimate reason to be in the kernel. I definitely agree that tracing MMIO is an extremely useful feature. I've implemented it myself once already for 2.4. -- Mathematics is the supreme nostalgia of our time.