From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx133.postini.com [74.125.245.133]) by kanga.kvack.org (Postfix) with SMTP id F244B6B0031 for ; Wed, 17 Jul 2013 21:49:16 -0400 (EDT) Received: from m1.gw.fujitsu.co.jp (unknown [10.0.50.71]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id 5EB563EE0C1 for ; Thu, 18 Jul 2013 10:49:14 +0900 (JST) Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 4BD2A45DE58 for ; Thu, 18 Jul 2013 10:49:14 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 1338A45DE5A for ; Thu, 18 Jul 2013 10:49:14 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id F0845E0800A for ; Thu, 18 Jul 2013 10:49:13 +0900 (JST) Received: from g01jpfmpwkw01.exch.g01.fujitsu.local (g01jpfmpwkw01.exch.g01.fujitsu.local [10.0.193.38]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id A4B0BE08008 for ; Thu, 18 Jul 2013 10:49:13 +0900 (JST) Message-ID: <51E74974.9050605@jp.fujitsu.com> Date: Thu, 18 Jul 2013 10:48:36 +0900 From: Yasuaki Ishimatsu MIME-Version: 1.0 Subject: Re: [PATCH] mm/hotplug, x86: Disable ARCH_MEMORY_PROBE by default References: <1374097503-25515-1-git-send-email-toshi.kani@hp.com> <1374103783.24916.49.camel@misato.fc.hp.com> <1374105078.24916.62.camel@misato.fc.hp.com> In-Reply-To: <1374105078.24916.62.camel@misato.fc.hp.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Toshi Kani Cc: KOSAKI Motohiro , Andrew Morton , "linux-mm@kvack.org" , LKML , x86@kernel.org, Tang Chen , "vasilis.liaskovitis" (2013/07/18 8:51), Toshi Kani wrote: > On Wed, 2013-07-17 at 19:33 -0400, KOSAKI Motohiro wrote: >> On Wed, Jul 17, 2013 at 7:29 PM, Toshi Kani wrote: >>> On Wed, 2013-07-17 at 19:22 -0400, KOSAKI Motohiro wrote: >>>> On Wed, Jul 17, 2013 at 5:45 PM, Toshi Kani wrote: >>>>> CONFIG_ARCH_MEMORY_PROBE enables /sys/devices/system/memory/probe >>>>> interface, which allows a given memory address to be hot-added as >>>>> follows. (See Documentation/memory-hotplug.txt for more detail.) >>>>> >>>>> # echo start_address_of_new_memory > /sys/devices/system/memory/probe >>>>> >>>>> This probe interface is required on powerpc. On x86, however, ACPI >>>>> notifies a memory hotplug event to the kernel, which performs its >>>>> hotplug operation as the result. Therefore, users should not be >>>>> required to use this interface on x86. This probe interface is also >>>>> error-prone that the kernel blindly adds a given memory address >>>>> without checking if the memory is present on the system; no probing >>>>> is done despite of its name. The kernel crashes when a user requests >>>>> to online a memory block that is not present on the system. >>>>> >>>>> This patch disables CONFIG_ARCH_MEMORY_PROBE by default on x86, >>>>> and clarifies it in Documentation/memory-hotplug.txt. >>>> >>>> Why don't you completely remove it? Who should use this strange interface? >>> >>> According to the comment below, this probe interface is used on powerpc. >>> So, we cannot remove it, but to disable it on x86. >> >> I meant x86. Why can't we completely remove ARCH_MEMORY_PROBE section >> from x86 Kconfig? > > Oh, I see what you meant. I do not expect any need for end-users, but I > was not sure if someone working on the memory hotplug development might > use it for fake hot-add testing. Yes, if you folks do not see any need, > I will remove it from x86 Kconfig. I do not think the interface is necessary. So I vote to Kosaki's opinion. Thanks, Yasuaki Ishimatsu > > Thanks, > -Toshi > -- 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