tree 2033082f51140f2337a85b29ac43b7b6a6cd581e
parent 2fd5485d93edab99ccea2e9abba038dc3f15a145
author Nathan Fontenot <nfont@linux.vnet.ibm.com> 1537211642 -0500
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1574671950 +0100

powerpc/pseries: Disable CPU hotplug across migrations

[ Upstream commit 85a88cabad57d26d826dd94ea34d3a785824d802 ]

When performing partition migrations all present CPUs must be online
as all present CPUs must make the H_JOIN call as part of the migration
process. Once all present CPUs make the H_JOIN call, one CPU is returned
to make the rtas call to perform the migration to the destination system.

During testing of migration and changing the SMT state we have found
instances where CPUs are offlined, as part of the SMT state change,
before they make the H_JOIN call. This results in a hung system where
every CPU is either in H_JOIN or offline.

To prevent this this patch disables CPU hotplug during the migration
process.

Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Reviewed-by: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>