Correct memory hot add/remove for powerpc

The current implementation of memory hot add and remove for powerpc is broken. This patch set both corrects this issue and updates the memory hot add and remove code for powerpc so that it can be done properly in the kernel.

The first two patches update the powerpc hot add and remove code to work with all of the updates that have gone in to enable memory remove with sparse vmemmap enabled. With these two patches applied the powerpc code is back to working, but not working properly.

The remaining patches update the powerpc memory add and remove code so the work can be done in the kernel and all while holding the memory hotplug lock. The current powerpc implementation does some of the work in the kernel and some of the work in userspace. While this code did work at one time, it has a problem in that it does part of the work to add and remove memory without holding the memory hotplug lock. In this scheme memory could be added and removed fast enough to cause the system to crash. This was a result of doing part of the add or remove without holding the lock.

In order to do memory hot remove in the kernel, this patch set introduces a sysfs release file (/sys/device/system/memory/release) which one can write the physical address of the memory to be removed to. Additionally there is a new set of flags defined for the memory notification chain to indicate that memory is being hot added or hot removed. This allows any work that may need to be done prior to or after memory is hot added or removed to be performed.

The remaining patches in the patch set update the powerpc to properly do memory hot add and remove in the kernel.

Nathan Fontenot

---
 Documentation/memory-hotplug.txt                      |   26 ++++
 arch/powerpc/mm/mem.c                                 |   35 +++++-
 arch/powerpc/platforms/pseries/hotplug-memory.c       |   95 +---------------
 drivers/base/memory.c                                 |   81 ++++++++++++--
 linux/Documentation/memory-hotplug.txt                |   34 ++++-
 linux/arch/powerpc/Kconfig                            |    2 
 linux/arch/powerpc/mm/init_64.c                       |    6 +
 linux/arch/powerpc/mm/mem.c                           |    9 +
 linux/arch/powerpc/platforms/pseries/dlpar.c          |  103 ++++++++++++++++++
 linux/arch/powerpc/platforms/pseries/hotplug-memory.c |   60 +---------
 linux/arch/x86/Kconfig                                |    2 
 linux/drivers/base/memory.c                           |   20 +--
 linux/include/linux/memory.h                          |    6 +
 linux/mm/Kconfig                                      |    2 
 linux/mm/memory_hotplug.c                             |   25 +++-
 15 files changed, 322 insertions(+), 184 deletions(-)

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