From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qc0-f175.google.com (mail-qc0-f175.google.com [209.85.216.175]) by kanga.kvack.org (Postfix) with ESMTP id 953356B0031 for ; Mon, 13 Jan 2014 15:31:26 -0500 (EST) Received: by mail-qc0-f175.google.com with SMTP id x13so5743153qcv.6 for ; Mon, 13 Jan 2014 12:31:26 -0800 (PST) Received: from mail-oa0-x231.google.com (mail-oa0-x231.google.com [2607:f8b0:4003:c02::231]) by mx.google.com with ESMTPS id h1si23465493qew.109.2014.01.13.12.31.25 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 13 Jan 2014 12:31:25 -0800 (PST) Received: by mail-oa0-f49.google.com with SMTP id n16so8488889oag.22 for ; Mon, 13 Jan 2014 12:31:25 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <52D32962.5050908@redhat.com> References: <1389380698-19361-1-git-send-email-prarit@redhat.com> <1389380698-19361-4-git-send-email-prarit@redhat.com> <52D32962.5050908@redhat.com> From: KOSAKI Motohiro Date: Mon, 13 Jan 2014 15:31:04 -0500 Message-ID: Subject: Re: [PATCH 2/2] x86, e820 disable ACPI Memory Hotplug if memory mapping is specified by user [v2] Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Prarit Bhargava 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" 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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org