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

[Michael Ellerman]

Michael Bringmann <mwb at linux.vnet.ibm.com> writes:
> On 1/29/19 3:37 AM, Michael Ellerman wrote:
>> Michael Bringmann <mwb at linux.vnet.ibm.com> writes:
>> 
>>> On 10/29/18 1:43 PM, 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>

Thanks.

cheers