From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757488AbYAJCDt (ORCPT ); Wed, 9 Jan 2008 21:03:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755427AbYAJCDl (ORCPT ); Wed, 9 Jan 2008 21:03:41 -0500 Received: from waste.org ([66.93.16.53]:39989 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754118AbYAJCDl (ORCPT ); Wed, 9 Jan 2008 21:03:41 -0500 Subject: Re: Replacement for page fault notifiers? From: Matt Mackall To: Arjan van de Ven Cc: Christoph Hellwig , Benjamin Herrenschmidt , Pavel Roskin , Dave Airlie , Pekka Paalanen , linux-kernel@vger.kernel.org, jbeulich@novell.com In-Reply-To: <20080109164241.7daa5770@laptopd505.fenrus.org> 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> Content-Type: text/plain Date: Wed, 09 Jan 2008 20:03:10 -0600 Message-Id: <1199930590.6245.104.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 16:42 -0800, Arjan van de Ven wrote: > On Wed, 9 Jan 2008 20:22:54 +0000 > Christoph Hellwig wrote: > > > On Thu, Jan 10, 2008 at 06:58:23AM +1100, Benjamin Herrenschmidt > > wrote: > > > It's a sane thing to do, Christoph, I don't think it's a > > > unreasonable request to put the hooks back in. > > > > As said a few times before there's simply no way we're going to put > > exactly that crap back. For one the patch removed a whole lot of > > crud from the kprobes code that simply isn't going to come back just > > because there are some pagefault notifiers. Second the page fault > > notifiers were horribly implemented and quite inefficient. And third > > we're not going to put something in just for out of tree code. > > > > I'm btw all in favor of making mmio tracing full fledged kernel infrastructure. > This doesn't mean "notifier" imo; this means a real flag in the struct page, > and then the page fault code can do > > if (page->flags & FLAG_MMIO_TRACED) > mmio_trace(page, regs, whatever..); 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. -- Mathematics is the supreme nostalgia of our time.