Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757815Ab3GYXF6 (ORCPT ); Thu, 25 Jul 2013 19:05:58 -0400 Received: from g4t0014.houston.hp.com ([15.201.24.17]:8701 "EHLO g4t0014.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757317Ab3GYXFy (ORCPT ); Thu, 25 Jul 2013 19:05:54 -0400 From: Toshi Kani To: mingo@kernel.org Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, dave@sr71.net, kosaki.motohiro@gmail.com, isimatu.yasuaki@jp.fujitsu.com, tangchen@cn.fujitsu.com, vasilis.liaskovitis@profitbricks.com, Toshi Kani Subject: [PATCH v3] mm/hotplug, x86: Disable ARCH_MEMORY_PROBE by default Date: Thu, 25 Jul 2013 17:04:34 -0600 Message-Id: <1374793474-11484-1-git-send-email-toshi.kani@hp.com> X-Mailer: git-send-email 1.8.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3770 Lines: 89 CONFIG_ARCH_MEMORY_PROBE enables the /sys/devices/system/memory/probe interface, which allows a given memory address to be hot-added as follows: # echo start_address_of_new_memory > /sys/devices/system/memory/probe (See Documentation/memory-hotplug.txt for more details.) 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 Acked-by: KOSAKI Motohiro Reviewed-by: Yasuaki Ishimatsu Cc: linux-mm@kvack.org Cc: dave@sr71.net Cc: tangchen@cn.fujitsu.com Cc: vasilis.liaskovitis@profitbricks.com --- Documentation/memory-hotplug.txt | 17 ++++++++++------- arch/x86/Kconfig | 7 ++++++- 2 files changed, 16 insertions(+), 8 deletions(-) diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt index 8e5eacb..d61e7d1 100644 --- a/Documentation/memory-hotplug.txt +++ b/Documentation/memory-hotplug.txt @@ -210,13 +210,16 @@ 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. Note that the probe interface does not verify if a specified address +is valid on the system. You need to be careful with this. 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/