From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757090AbYIDUXx (ORCPT ); Thu, 4 Sep 2008 16:23:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755969AbYIDUXS (ORCPT ); Thu, 4 Sep 2008 16:23:18 -0400 Received: from extu-mxob-2.symantec.com ([216.10.194.135]:34936 "EHLO extu-mxob-2.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757220AbYIDUXO (ORCPT ); Thu, 4 Sep 2008 16:23:14 -0400 Date: Thu, 4 Sep 2008 21:23:01 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.site To: =?UTF-8?Q?Rafa=C5=82_Mi=C5=82ecki?= cc: Alan Jenkins , Alan Cox , Jeremy Fitzhardinge , Yinghai Lu , Ingo Molnar , "H. Peter Anvin" , Linux Kernel Mailing List Subject: Re: [PATCH RFC] x86: check for and defend against BIOS memory corruption In-Reply-To: Message-ID: References: <48B701FB.2020905@goop.org> <86802c440808281849nb972d64te89894077ea9f33c@mail.gmail.com> <48B76CE0.5010309@goop.org> <20080829102547.655440bf@lxorguk.ukuu.org.uk> <48B7E6EE.9090901@tuffmail.co.uk> MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="8323584-1293509426-1220559781=:3012" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323584-1293509426-1220559781=:3012 Content-Type: TEXT/PLAIN; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE On Thu, 4 Sep 2008, Rafa=C5=82 Mi=C5=82ecki wrote: > > 2008/8/29 Rafa=C5=82 Mi=C5=82ecki : > > 2008/8/29 Hugh Dickins : > >> Here's my version of Jeremy's patch, that I've now tested on my machin= es, > >> as x86_32 and as x86_64. It addresses none of the points Alan Cox mad= e, > >> and it stays silent for me, even after suspend+resume, unless I actual= ly > >> introduce corruption myself. Omits Jeremy's check in fault.c, but doe= s > >> a check every minute, so should soon detect Rafa=C5=82's HDMI corrupti= on > >> without any need to suspend+resume. > > > > Your periodic test works fine: > > > > Corrupted low memory at ffff88000000be9c (be9c phys) =3D b02a0004 > > [] check_for_bios_corruption+0x93/0x9f > > [] ? periodic_check_for_corruption+0x0/0x25 > > [] periodic_check_for_corruption+0x9/0x25 > > > > By the way I confirmed this bug on Sony Vaio FW11M (my one is FW11S). > > Probably more machines from FW11* are affected. >=20 > If this patch is known to work fine for Sony Vaio FW* and Alan's > machine, could it go mainline somehow? Well. Thanks for the prod, and I'm certainly remiss for not following up sooner. But I'm really not at all keen on such a patch going into mainline myself. It's an interesting experiment, and I'd be happy to see such a patch (adjusted to make sure output goes to kerneloops.org) spending a little while in Fedora Rawhide (who'd be the right contact for that?). But so far as mainline goes, I share Alan Cox's opinion that we should not be chopping pages out of every x86 user's memory, just because a couple of machines with faulty BIOSes have been observed. Particularly now it's evident that the 64kB "limit" is no more than a reflection of where the directmap pagetable changes have caught such corruption. If lots more such corruptions are reported, of course I would change my position; but those bad directmap PMD crashes are themselves quite recognizable now we know to look out for them. I would prefer you both to use the minimal memmap=3D solutions for now; but others may disagree. Hugh --8323584-1293509426-1220559781=:3012--