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authorToshi Kani <toshi.kani@hp.com>2013-07-19 11:47:48 -0600
committerIngo Molnar <mingo@kernel.org>2013-07-22 11:13:34 +0200
commita0842b704b0f7c2d925473676f2012ea5dc39976 (patch)
tree6abaf5122cd924cbe083b168ea3e94264b6d6b73 /Documentation/memory-hotplug.txt
parent3b2f64d00c46e1e4e9bd0bb9bb12619adac27a4b (diff)
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>
Diffstat (limited to 'Documentation/memory-hotplug.txt')
-rw-r--r--Documentation/memory-hotplug.txt16
1 files changed, 9 insertions, 7 deletions
diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
index 8e5eacbdcfa3..8fd254c73589 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