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 <toshi.kani@xxxxxx> Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx> Cc: linux-mm@xxxxxxxxx Cc: dave@xxxxxxxx Cc: tangchen@xxxxxxxxxxxxxx Cc: vasilis.liaskovitis@xxxxxxxxxxxxxxxx --- 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>