Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752902Ab3GWAZh (ORCPT ); Mon, 22 Jul 2013 20:25:37 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:56760 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751589Ab3GWAZg (ORCPT ); Mon, 22 Jul 2013 20:25:36 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v2.0.1 X-SHieldMailCheckerPolicyVersion: FJ-ISEC-20120718-3 Message-ID: <51EDCD46.5040502@jp.fujitsu.com> Date: Tue, 23 Jul 2013 09:24:38 +0900 From: Yasuaki Ishimatsu User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130620 Thunderbird/17.0.7 MIME-Version: 1.0 To: Toshi Kani CC: , , , , , , , 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 X-SecurityPolicyCheck-GC: OK by FENCE-Mail Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3694 Lines: 87 (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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/