linux-kernel - Re: [PATCH v2] mm/hotplug, x86: Disable ARCH_MEMORY

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Date:	Mon, 22 Jul 2013 10:37:22 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Toshi Kani <toshi.kani@...com>
Cc:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, x86@...nel.org, dave@...1.net,
	kosaki.motohiro@...il.com, isimatu.yasuaki@...fujitsu.com,
	tangchen@...fujitsu.com, vasilis.liaskovitis@...fitbricks.com
Subject: Re: [PATCH v2] mm/hotplug, x86: Disable ARCH_MEMORY_PROBE by default


* Toshi Kani <toshi.kani@...com> wrote:

> CONFIG_ARCH_MEMORY_PROBE enables /sys/devices/system/memory/probe
> interface, which allows a given memory address to be hot-added as
> follows. (See Documentation/memory-hotplug.txt for more detail.)
> 
> # echo start_address_of_new_memory > /sys/devices/system/memory/probe
> 
> 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.

Could we please also fix it to never crash the kernel, even if stupid 
ranges are provided?

Thanks,

	Ingo
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