From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762887AbXGKKUo (ORCPT ); Wed, 11 Jul 2007 06:20:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760690AbXGKKU0 (ORCPT ); Wed, 11 Jul 2007 06:20:26 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:49069 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760331AbXGKKUY (ORCPT ); Wed, 11 Jul 2007 06:20:24 -0400 From: "Rafael J. Wysocki" To: Al Boldi Subject: Re: Hibernation Redesign Date: Wed, 11 Jul 2007 12:27:51 +0200 User-Agent: KMail/1.9.5 Cc: Jeremy Fitzhardinge , Jeremy Maitin-Shepard , Pavel Machek , Nick Piggin , linux-kernel@vger.kernel.org, Andrew Morton References: <200707081737.21932.a1426z@gawab.com> <46940F45.3090005@goop.org> <200707110711.26767.a1426z@gawab.com> In-Reply-To: <200707110711.26767.a1426z@gawab.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200707111227.52609.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, 11 July 2007 06:11, Al Boldi wrote: > Jeremy Fitzhardinge wrote: > > Jeremy Maitin-Shepard wrote: > > > In > > > addition, I recall that the Linux boot procedure on x86 and on some > > > other platforms necessarily uses certain low-address memory, like the > > > first 640K, which must be backed up regardless. > > > > Well, the traditional framebuffer/ISA space between 640k and 1M probably > > needs to be identity mapped, but I don't think there's anything in there > > which specifically needs to be save/restored (except framebuffer > > contents, maybe?). > > > > > For these reasons, it seems that it would be easiest to simply backup > > > the first e.g. 16 or 64 MB of memory, and not have to worry about > > > loading the kernel at a non-standard address and specifying a > > > complicated exact memmap. Someone might prove me wrong, though. > > > > Yes, I suppose. You're certain the old kernel's devices are completely > > quiescent at that point? > > That's exactly the problem; trying to save a state from within the kernel > would probably necessitate a freezer hack, which we are trying so dearly to > avoid. Well, I don't think that avoiding the freezer whatever it takes would be a good idea. There needs to be some balance. ;-) > The only way the kexec approach may be successful, is by completely relying > on the kexec'd hibernate-mode kernel to save state, otherwise we would be > back to square one. And if that required a special boot procedure for the > kexec'd hibernate-mode kernel, then why not? Because such things are very difficult for many users. My experience with the userland suspend shows that clearly. Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth