Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760919Ab3GSRss (ORCPT ); Fri, 19 Jul 2013 13:48:48 -0400 Received: from g5t0006.atlanta.hp.com ([15.192.0.43]:25074 "EHLO g5t0006.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751540Ab3GSRsr (ORCPT ); Fri, 19 Jul 2013 13:48:47 -0400 From: Toshi Kani To: akpm@linux-foundation.org Cc: 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 v2] mm/hotplug, x86: Disable ARCH_MEMORY_PROBE by default Date: Fri, 19 Jul 2013 11:47:48 -0600 Message-Id: <1374256068-26016-1-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: 3399 Lines: 77 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 --- 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/