BugLink: http://bugs.launchpad.net/bugs/1537881
https://lists.ozlabs.org/pipermail/linuxppc-dev/2016-January/138011.html

When secondaries are napping in kvm_unsplit_nap() with hwthread_req = 1,
the HMI goes ignored even though subcores are already exited the guest.
Hence HMI keeps waking up secondaries from nap in a loop and secondaries
always go back to nap since no vcore is assigned to them. This makes
impossible for primary thread to get hold of secondary threads resulting
into a soft lockup in KVM path.

This patch fixes this by adding a HMI check just before the thread goes
to unsplit nap.
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>