From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx148.postini.com [74.125.245.148]) by kanga.kvack.org (Postfix) with SMTP id 798576B0032 for ; Mon, 22 Jul 2013 20:25:36 -0400 (EDT) Received: from m4.gw.fujitsu.co.jp (unknown [10.0.50.74]) by fgwmail6.fujitsu.co.jp (Postfix) with ESMTP id 534043EE0BB for ; Tue, 23 Jul 2013 09:25:34 +0900 (JST) Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 42E3245DE51 for ; Tue, 23 Jul 2013 09:25:34 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 2221E45DE4D for ; Tue, 23 Jul 2013 09:25:34 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 140F2E08003 for ; Tue, 23 Jul 2013 09:25:34 +0900 (JST) Received: from g01jpfmpwkw03.exch.g01.fujitsu.local (g01jpfmpwkw03.exch.g01.fujitsu.local [10.0.193.57]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id B692E1DB8037 for ; Tue, 23 Jul 2013 09:25:33 +0900 (JST) Message-ID: <51EDCD46.5040502@jp.fujitsu.com> Date: Tue, 23 Jul 2013 09:24:38 +0900 From: Yasuaki Ishimatsu MIME-Version: 1.0 Subject: Re: [PATCH v2] mm/hotplug, x86: Disable ARCH_MEMORY_PROBE by default References: <1374256068-26016-1-git-send-email-toshi.kani@hp.com> In-Reply-To: <1374256068-26016-1-git-send-email-toshi.kani@hp.com> Content-Type: text/plain; charset="ISO-2022-JP" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Toshi Kani Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, dave@sr71.net, kosaki.motohiro@gmail.com, tangchen@cn.fujitsu.com, vasilis.liaskovitis@profitbricks.com (2013/07/20 2:47), 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, regular users do not need > this interface on x86. This probe interface is also error-prone and > misleading 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 interface is > currently used for testing as it can fake a hotplug event. > > This patch disables CONFIG_ARCH_MEMORY_PROBE by default on x86, adds > its Kconfig menu entry on x86, and clarifies its use in Documentation/ > memory-hotplug.txt. > > Signed-off-by: Toshi Kani Reviewed-by: Yasuaki Ishimatsu Thanks, Yasuaki Ishimatsu > --- > Documentation/memory-hotplug.txt | 16 +++++++++------- > arch/x86/Kconfig | 7 ++++++- > 2 files changed, 15 insertions(+), 8 deletions(-) > > diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt > index 8e5eacb..8fd254c 100644 > --- a/Documentation/memory-hotplug.txt > +++ b/Documentation/memory-hotplug.txt > @@ -210,13 +210,15 @@ If memory device is found, memory hotplug code will be called. > > 4.2 Notify memory hot-add event by hand > ------------ > -In some environments, especially virtualized environment, firmware will not > -notify memory hotplug event to the kernel. For such environment, "probe" > -interface is supported. This interface depends on CONFIG_ARCH_MEMORY_PROBE. > - > -Now, CONFIG_ARCH_MEMORY_PROBE is supported only by powerpc but it does not > -contain highly architecture codes. Please add config if you need "probe" > -interface. > +On powerpc, the firmware does not notify a memory hotplug event to the kernel. > +Therefore, "probe" interface is supported to notify the event to the kernel. > +This interface depends on CONFIG_ARCH_MEMORY_PROBE. > + > +CONFIG_ARCH_MEMORY_PROBE is supported on powerpc only. On x86, this config > +option is disabled by default since ACPI notifies a memory hotplug event to > +the kernel, which performs its hotplug operation as the result. Please > +enable this option if you need the "probe" interface for testing purposes > +on x86. > > Probe interface is located at > /sys/devices/system/memory/probe > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index b32ebf9..408ef68 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -1344,8 +1344,13 @@ config ARCH_SELECT_MEMORY_MODEL > depends on ARCH_SPARSEMEM_ENABLE > > config ARCH_MEMORY_PROBE > - def_bool y > + bool "Enable sysfs memory/probe interface" > + default n > depends on X86_64 && MEMORY_HOTPLUG > + help > + This option enables a sysfs memory/probe interface for testing. > + See Documentation/memory-hotplug.txt for more information. > + If you are unsure how to answer this question, answer N. > > config ARCH_PROC_KCORE_TEXT > def_bool y > -- 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