From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261518AbVCCIBE (ORCPT ); Thu, 3 Mar 2005 03:01:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261540AbVCCIBE (ORCPT ); Thu, 3 Mar 2005 03:01:04 -0500 Received: from grendel.digitalservice.pl ([217.67.200.140]:58325 "HELO mail.digitalservice.pl") by vger.kernel.org with SMTP id S261518AbVCCIAz (ORCPT ); Thu, 3 Mar 2005 03:00:55 -0500 From: "Rafael J. Wysocki" To: Pavel Machek Subject: Re: BIOS overwritten during resume (was: Re: Asus L5D resume on battery power) Date: Thu, 3 Mar 2005 09:02:47 +0100 User-Agent: KMail/1.7.1 Cc: Andi Kleen , kernel list , paul.devriendt@amd.com References: <200502252237.04110.rjw@sisk.pl> <200503030047.43625.rjw@sisk.pl> <20050302235456.GB1439@elf.ucw.cz> In-Reply-To: <20050302235456.GB1439@elf.ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200503030902.48038.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Thursday, 3 of March 2005 00:54, Pavel Machek wrote: > Hi! > > > > > It seems that we write to the BIOS while moving the image, at least on my box, > > > > which is quite not correct, IMO. > > [-- snip --] > > > > > > > > IMO this may lead to unexpected results, like the mysterious reboots during > > > > resume. > > > > > > Well, I always thought that ROM-BIOS is expected to > > > be... well... read-only? Can you really write to your BIOS? [I know > > > about Flash-BIOSen, but they are certainly not writable by "normal" > > > write.] Plus we should overwrite it with same values... > > > > > > Anyway, IMO bios should be marked as reserved (and we should not be > > > touching reserved pages). Can you verify that your BIOS is properly > > > marked reserved? [Ccing l-k, this might be interesting.] > > > > It is, but that's even more interesting. Namely, the BIOS-e820 memory map > > looks as follows: > > > > BIOS-provided physical RAM map: > > BIOS-e820: 0000000000000000 - 000000000009fc00 (usable) > > BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved) > > BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved) > > BIOS-e820: 0000000000100000 - 000000001ff40000 (usable) > > BIOS-e820: 000000001ff40000 - 000000001ff50000 (ACPI data) > > BIOS-e820: 000000001ff50000 - 0000000020000000 (ACPI NVS) > > BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved) > > BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved) > > > > and the pages in the first two reserved areas are properly marked as reserved. > > Moreover, there is an apparent hole between a0000 and e0000 which also > > is marked as reserved. However, we treat all of these pages as saveable > > (a page is treated as non-saveable if it is marked as reserved _and_ satisfies > > specific condition which is met by only one page on my system). Consequently, > > during resume we try to overwrite all of these pages and we not only try to > > write to (theoretically) read-only areas, but also we try to write to where there's > > nothing. :-) > > > > Still, there are almost 3500 reserved pages on my system and I'm not sure that > > we don't need to save at least some of them. Anyway, I'm attaching the full > > list of pages that are marked as reserved and treated as saveable, so they get > > overwritten during resume. Please have a look (these are virtual x86-64 > > addresses, but the mapping is straightforward). > > [looking at code] > > IIRC kernel code/data is marked as PageReserved(), that's why we need > to save that :(. Not sure what to do with data e820 marked as > reserved... Perhaps we need another page flag, like PG_readonly, and mark the pages reserved by the e820 as PG_reserved | PG_readonly (the same for the areas that are not returned by e820 at all). Would that be acceptable? Greets, Rafael -- - Would you tell me, please, which way I ought to go from here? - That depends a good deal on where you want to get to. -- Lewis Carroll "Alice's Adventures in Wonderland"