Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752250AbaAMXkT (ORCPT ); Mon, 13 Jan 2014 18:40:19 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37941 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750821AbaAMXkQ (ORCPT ); Mon, 13 Jan 2014 18:40:16 -0500 Message-ID: <52D4793E.8070102@redhat.com> Date: Mon, 13 Jan 2014 18:39:42 -0500 From: Prarit Bhargava User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110419 Red Hat/3.1.10-1.el6_0 Thunderbird/3.1.10 MIME-Version: 1.0 To: KOSAKI Motohiro CC: Bodo Eggert <7eggert@gmx.de>, LKML , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , the arch/x86 maintainers , Len Brown , "Rafael J. Wysocki" , Linn Crosetto , Pekka Enberg , Yinghai Lu , Andrew Morton , Toshi Kani , Tang Chen , Wen Congyang , Vivek Goyal , dyoung@redhat.com, linux-acpi@vger.kernel.org, "linux-mm@kvack.org" Subject: Re: [PATCH 2/2] x86, e820 disable ACPI Memory Hotplug if memory mapping is specified by user [v2] References: <1389380698-19361-1-git-send-email-prarit@redhat.com> <1389380698-19361-4-git-send-email-prarit@redhat.com> <52D32962.5050908@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/13/2014 03:31 PM, KOSAKI Motohiro wrote: > On Sun, Jan 12, 2014 at 6:46 PM, Prarit Bhargava wrote: >> >> >> On 01/11/2014 11:35 AM, 7eggert@gmx.de wrote: >>> >>> >>> On Fri, 10 Jan 2014, Prarit Bhargava wrote: >>> >>>> kdump uses memmap=exactmap and mem=X values to configure the memory >>>> mapping for the kdump kernel. If memory is hotadded during the boot of >>>> the kdump kernel it is possible that the page tables for the new memory >>>> cause the kdump kernel to run out of memory. >>>> >>>> Since the user has specified a specific mapping ACPI Memory Hotplug should be >>>> disabled in this case. >>> >>> I'll ask just in case: Is it possible to want memory hotplug in spite of >>> using memmap=exactmap or mem=X? >> >> Good question -- I can't think of a case. When a user specifies "memmap" or >> "mem" IMO they are asking for a very specific memory configuration. Having >> extra memory added above what the user has specified seems to defeat the purpose >> of "memmap" and "mem". > > May be yes, may be no. > > They are often used for a wrokaround to avoid broken firmware issue. > If we have no way > to explicitly enable hotplug. We will lose a workaround. > > Perhaps, there is no matter. Today, memory hotplug is only used on > high-end machine > and their firmware is carefully developped and don't have a serious > issue almostly. Though. Oof -- sorry Kosaki :( I didn't see this until just now (and your subsequent ACK on the updated patch). I just remembered that we did have a processor vendor's whitebox that would not boot unless we specified a specific memmap and we did specify memmap=exactmap to boot the system correctly and the system had hotplug memory. So it means that I should not key off of "memmap=exactmap". I will self-NAK the updated patch and submit a new one. P. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/