From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753516Ab3KLAEU (ORCPT ); Mon, 11 Nov 2013 19:04:20 -0500 Received: from mga02.intel.com ([134.134.136.20]:60471 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751369Ab3KLAEN (ORCPT ); Mon, 11 Nov 2013 19:04:13 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.93,535,1378882800"; d="scan'208";a="407146160" Message-ID: <5281707D.1040604@linux.intel.com> Date: Mon, 11 Nov 2013 16:04:13 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Ingo Molnar CC: Olof Johansson , "linux-kernel@vger.kernel.org" Subject: Re: Corrupted low memory in v3.9+ References: <52603CD6.6080507@linux.intel.com> <527BEA91.6050603@linux.intel.com> <20131111113503.GA16090@gmail.com> <528168CB.7070602@linux.intel.com> In-Reply-To: <528168CB.7070602@linux.intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/11/2013 03:31 PM, H. Peter Anvin wrote: > On 11/11/2013 03:35 AM, Ingo Molnar wrote: > > Oops! I had misunderstood how the checker worked -- I thought it > checked the *reserved* memory, but it in fact reserves memory > *independently* and then checks it. > And now I understand why I had that misconception: > Periodically check for memory corruption in low memory, which > is suspected to be caused by BIOS. Even when enabled in the > configuration, it is disabled at runtime. Enable it by > setting "memory_corruption_check=1" on the kernel command > line. By default it scans the low 64k of memory every 60 > seconds; see the memory_corruption_check_size and > memory_corruption_check_period parameters in > Documentation/kernel-parameters.txt to adjust this. This makes it sound like it scans the low 64K when it is turned on, i.e. the bit that is reserved by default. I think we should change that default too to 640K. I will post a patchset shortly. -hpa