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mm/hotplug, x86: Disable ARCH_MEMORY_PROBE by default

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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>
This commit is contained in:
Toshi Kani 2013-07-19 11:47:48 -06:00 committed by Ingo Molnar
parent 3b2f64d00c
commit a0842b704b
2 changed files with 13 additions and 7 deletions
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14
Documentation/memory-hotplug.txt
View File

@ -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.
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.
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.
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

6
arch/x86/Kconfig
View File

@ -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