From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx141.postini.com [74.125.245.141]) by kanga.kvack.org (Postfix) with SMTP id E95416B0031 for ; Thu, 18 Jul 2013 12:03:09 -0400 (EDT) Message-ID: <1374163339.24916.65.camel@misato.fc.hp.com> Subject: Re: [PATCH] mm/hotplug, x86: Disable ARCH_MEMORY_PROBE by default From: Toshi Kani Date: Thu, 18 Jul 2013 10:02:19 -0600 In-Reply-To: <51E74974.9050605@jp.fujitsu.com> 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> <51E74974.9050605@jp.fujitsu.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Yasuaki Ishimatsu Cc: KOSAKI Motohiro , Andrew Morton , "linux-mm@kvack.org" , LKML , x86@kernel.org, Tang Chen , "vasilis.liaskovitis" On Thu, 2013-07-18 at 10:48 +0900, Yasuaki Ishimatsu wrote: > (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 for the confirmation! -Toshi > > 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