mm/hotplug, x86: Disable ARCH_MEMORY_PROBE by default (a0842b70) · Commits · 戴 / test

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@hp.com> Acked-by:

KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: linux-mm@kvack.org Cc: dave@sr71.net Cc: isimatu.yasuaki@jp.fujitsu.com Cc: tangchen@cn.fujitsu.com Cc: vasilis.liaskovitis@profitbricks.com Link: http://lkml.kernel.org/r/1374256068-26016-1-git-send-email-toshi.kani@hp.com [ Edited it slightly. ] Signed-off-by:

Ingo Molnar <mingo@kernel.org>

Documentation/memory-hotplug.txt

+9 −7

Original line number	Diff line number	Diff line
		@@ -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

arch/x86/Kconfig

+5 −1

Original line number	Diff line number	Diff line
		@@ -1344,8 +1344,12 @@ config ARCH_SELECT_MEMORY_MODEL
		depends on ARCH_SPARSEMEM_ENABLE

		config ARCH_MEMORY_PROBE
		def_bool y
		bool "Enable sysfs memory/probe interface"
		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

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