powerpc/pseries: Perform full re-add of CPU for topology update post-migration

[Michael Ellerman]

On Mon, 2018-10-29 at 18:43:36 UTC, Nathan Fontenot wrote:
> On pseries systems, performing a partition migration can result in
> altering the nodes a CPU is assigned to on the destination system. For
> exampl, pre-migration on the source system CPUs are in node 1 and 3,
> post-migration on the destination system CPUs are in nodes 2 and 3.
> 
> Handling the node change for a CPU can cause corruption in the slab
> cache if we hit a timing where a CPUs node is changed while cache_reap()
> is invoked. The corruption occurs because the slab cache code appears
> to rely on the CPU and slab cache pages being on the same node.
> 
> The current dynamic updating of a CPUs node done in arch/powerpc/mm/numa.c
> does not prevent us from hitting this scenario.
> 
> Changing the device tree property update notification handler that
> recognizes an affinity change for a CPU to do a full DLPAR remove and
> add of the CPU instead of dynamically changing its node resolves this
> issue.
> 
> Signed-off-by: Nathan Fontenot <nfont at linux.vnet.ibm.com>
> Signed-off-by: Michael W. Bringmann <mwb at linux.vnet.ibm.com>
> Tested-by: Michael W. Bringmann <mwb at linux.vnet.ibm.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/81b61324922c67f73813d8a9c175f3c1

cheers