linux-kernel - [PATCH 0/4] acpi,memory-hotplug : implement framework for hot removing memory

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Date:	Wed, 3 Oct 2012 18:52:40 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	<x86@...nel.org>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>, <linux-acpi@...r.kernel.org>
CC:	<rientjes@...gle.com>, <liuj97@...il.com>, <len.brown@...el.com>,
	<cl@...ux.com>, <minchan.kim@...il.com>,
	<akpm@...ux-foundation.org>, <kosaki.motohiro@...fujitsu.com>,
	<wency@...fujitsu.com>
Subject: [PATCH 0/4] acpi,memory-hotplug : implement framework for hot removing
 memory

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.

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