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mm/hotplug, x86: Disable ARCH_MEMORY_PROBE by default
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>
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@ -210,13 +210,15 @@ If memory device is found, memory hotplug code will be called.
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4.2 Notify memory hot-add event by hand
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------------
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In some environments, especially virtualized environment, firmware will not
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notify memory hotplug event to the kernel. For such environment, "probe"
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interface is supported. This interface depends on CONFIG_ARCH_MEMORY_PROBE.
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On powerpc, the firmware does not notify a memory hotplug event to the kernel.
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Therefore, "probe" interface is supported to notify the event to the kernel.
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This interface depends on CONFIG_ARCH_MEMORY_PROBE.
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Now, CONFIG_ARCH_MEMORY_PROBE is supported only by powerpc but it does not
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contain highly architecture codes. Please add config if you need "probe"
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interface.
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CONFIG_ARCH_MEMORY_PROBE is supported on powerpc only. On x86, this config
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option is disabled by default since ACPI notifies a memory hotplug event to
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the kernel, which performs its hotplug operation as the result. Please
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enable this option if you need the "probe" interface for testing purposes
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on x86.
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Probe interface is located at
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/sys/devices/system/memory/probe
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@ -1344,8 +1344,12 @@ config ARCH_SELECT_MEMORY_MODEL
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depends on ARCH_SPARSEMEM_ENABLE
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config ARCH_MEMORY_PROBE
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def_bool y
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bool "Enable sysfs memory/probe interface"
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depends on X86_64 && MEMORY_HOTPLUG
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help
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This option enables a sysfs memory/probe interface for testing.
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See Documentation/memory-hotplug.txt for more information.
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If you are unsure how to answer this question, answer N.
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config ARCH_PROC_KCORE_TEXT
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def_bool y
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