From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752703AbaEUSE2 (ORCPT ); Wed, 21 May 2014 14:04:28 -0400 Received: from terminus.zytor.com ([198.137.202.10]:39943 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751018AbaEUSE0 (ORCPT ); Wed, 21 May 2014 14:04:26 -0400 User-Agent: K-9 Mail for Android In-Reply-To: References: <537CE3C2.8030601@zytor.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Subject: Re: Bisected 3.9 regression: Corrupted low memory (x86, mm: Move reserving low memory later in initialization) From: "H. Peter Anvin" Date: Wed, 21 May 2014 11:03:59 -0700 To: =?UTF-8?Q?Rafa=C5=82_Mi=C5=82ecki?= CC: Linux Kernel Mailing List , Thomas Gleixner , Ingo Molnar , x86@kernel.org Message-ID: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Yes, I'm sure. The old memory reservation code kept the checker from working. On May 21, 2014 10:58:39 AM PDT, "Rafał Miłecki" wrote: >On 21 May 2014 19:34, H. Peter Anvin wrote: >> On 05/21/2014 06:31 AM, Rafał Miłecki wrote: >>> On 16 May 2014 07:29, Rafał Miłecki wrote: >>>> Sorry for the late report, this bug appears on my old notebook I >don't >>>> commonly use. Anyway, I've noticed following problem when using >>>> 3.15-rc1: >>>> >>>> Corrupted low memory at ffff88000000be98 (be98 phys) = >b02a000400000000 >>> >>> Ping? >>> >> >> It's not a regression, but rather a progression: the checker now does >> what it claims to do, which is to check for low memory corruption. >> >> However, the checker is also rather useless as anything other than a >> diagnostic tool. It tells you that your BIOS is corrupting memory, >and >> the solution to that is to reserve the memory, which we already do. >> >> All the checker tells us is that on your system, yes, we really do >need >> to reserve the memory. > >What about making checker a bit more user friendly? > >First of all, I got many repeated messages like: >Corrupted low memory at (...) >In the first e-mail you can see ~10 of them and I really got more. > >Secondly, if this is just a confirmation that low memory reservation >was indeed needed, what about making it debugging only? Right now it >sounds like an error for end-users. What about making it something >like >Low memory reservation prevented corruption at (...) > >The last question, just for sure... are you convinced what I'm seeing >is not any kind of error? After all, it started appearing after commit >that moves memory reservation. It's not a commit that enabled the >checker or something like that. >What it seems to be for someone not experienced is a bit opposite. It >looks that after commit in question, kernel reserves low memory too >late and BIOS already corrupts some data placed in it. >However I'm not on expert, so I'll just listen to your opinion. I >simply wanted to ask, just to be sure everything is alright. -- Sent from my mobile phone. Please pardon brevity and lack of formatting.