From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752923AbbL1WVO (ORCPT ); Mon, 28 Dec 2015 17:21:14 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:41357 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752890AbbL1WVK (ORCPT ); Mon, 28 Dec 2015 17:21:10 -0500 Date: Mon, 28 Dec 2015 14:21:08 -0800 From: Andrew Morton To: Taku Izumi Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, tony.luck@intel.com, qiuxishi@huawei.com, kamezawa.hiroyu@jp.fujitsu.com, mel@csn.ul.ie, dave.hansen@intel.com, matt@codeblueprint.co.uk Subject: Re: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option Message-Id: <20151228142108.fa679ebf9d3a91ad14924977@linux-foundation.org> In-Reply-To: <1449631177-14863-1-git-send-email-izumi.taku@jp.fujitsu.com> References: <1449631109-14756-1-git-send-email-izumi.taku@jp.fujitsu.com> <1449631177-14863-1-git-send-email-izumi.taku@jp.fujitsu.com> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 9 Dec 2015 12:19:37 +0900 Taku Izumi wrote: > This patch extends existing "kernelcore" option and > introduces kernelcore=mirror option. By specifying > "mirror" instead of specifying the amount of memory, > non-mirrored (non-reliable) region will be arranged > into ZONE_MOVABLE. > > v1 -> v2: > - Refine so that the following case also can be > handled properly: > > Node X: |MMMMMM------MMMMMM--------| > (legend) M: mirrored -: not mirrrored > > In this case, ZONE_NORMAL and ZONE_MOVABLE are > arranged like bellow: > > Node X: |MMMMMM------MMMMMM--------| > |ooooooxxxxxxooooooxxxxxxxx| ZONE_NORMAL > |ooooooxxxxxxoooooooo| ZONE_MOVABLE > (legend) o: present x: absent > > v2 -> v3: > - change the option name from kernelcore=reliable > into kernelcore=mirror > - documentation fix so that users can understand > nn[KMS] and mirror are exclusive My earlier concern with this approach is the assumption that *all* of the mirrored memory will be used to kernelcore. The user might want to use half the machine's mirrored memory for kernelcore and half for regular memory but cannot do so. However I think what I'm seeing from the discussion is that in this case, the user can alter the amount of mirrored memory via EFI to achieve the same effect. Is this correct? If so, should we document this somewhere and provide our users with instructions on how to make the required EFI changes? Or is this all so totally obvious to them that there is no need?