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

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Date:	Wed, 17 Jul 2013 19:22:12 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Toshi Kani <toshi.kani@...com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	vasilis.liaskovitis@...fitbricks.com
Subject: Re: [PATCH] mm/hotplug, x86: Disable ARCH_MEMORY_PROBE by default

On Wed, Jul 17, 2013 at 5:45 PM, 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, users should not be
> required to use this interface on x86. This probe interface is also
> error-prone 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 patch disables CONFIG_ARCH_MEMORY_PROBE by default on x86,
> and clarifies it in Documentation/memory-hotplug.txt.

Why don't you completely remove it? Who should use this strange interface?
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