From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Subject: [PATCH 0/4] acpi,memory-hotplug : implement framework for hot removing
 memory
Date: Wed, 3 Oct 2012 18:52:40 +0900
Message-ID: <506C0AE8.40702@jp.fujitsu.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="ISO-2022-JP"
Content-Transfer-Encoding: 7bit
Sender: linux-acpi-owner@vger.kernel.org
To: x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org
Cc: rientjes@google.com, liuj97@gmail.com, len.brown@intel.com, cl@linux.com, minchan.kim@gmail.com, akpm@linux-foundation.org, kosaki.motohiro@jp.fujitsu.com, wency@cn.fujitsu.com

We are trying to implement a physical memory hot removing function as
following thread.

https://lkml.org/lkml/2012/9/5/201

But there is not enough review to merge into linux kernel.

I think there are following blockades.
  1. no physical memory hot removable system
  2. huge patch-set

If you have a KVM system, we can get rid of 1st blockade. Because
applying following patch, we can create memory hot removable system
on KVM guest.

http://lists.gnu.org/archive/html/qemu-devel/2012-07/msg01389.html

2nd blockade is own problem. So we try to divide huge patch into
a small patch in each function as follows: 

 - bug fix
 - acpi framework
 - kernel core

We had already sent bug fix patches.
https://lkml.org/lkml/2012/9/27/39
https://lkml.org/lkml/2012/10/2/83

The patch-set implements a framework for hot removing memory.

The memory device can be removed by 2 ways:
1. send eject request by SCI
2. echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject

In the 1st case, acpi_memory_disable_device() will be called.
In the 2nd case, acpi_memory_device_remove() will be called.
acpi_memory_device_remove() will also be called when we unbind the
memory device from the driver acpi_memhotplug.

acpi_memory_disable_device() has already implemented a code which
offlines memory and releases acpi_memory_info struct . But
acpi_memory_device_remove() has not implemented it yet.

So the patch prepares the framework for hot removing memory and
adds the framework intoacpi_memory_device_remove(). And it prepares
remove_memory(). But the function does nothing because we cannot
support memory hot remove.