Updates for powerpc/pseries: hotplug cpu
Bugzilla: https://bugzilla.redhat.com/2166730
Build Info: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=51161129
Tested: Verified Brew build test kernel RPMs and confirmed issue is resovled
Signed-off-by: Mamatha Inamdar minamdar@redhat.com
commit f6aa37c51ec0d053ee34c235bfe0e666618a3baf Author: Laurent Dufour ldufour@linux.ibm.com Date: Mon Nov 14 17:01:50 2022 +0100
powerpc/pseries: unregister VPA when hot unplugging a CPU
The VPA should unregister when offlining a CPU. Otherwise there could be
a short window where 2 CPUs could share the same VPA.
This happens because the hypervisor is still keeping the VPA attached to
the vCPU even if it became offline.
Here is a potential situation:
1. remove proc A,
2. add proc B. If proc B gets proc A's place in cpu_present_mask, then
it registers proc A's VPAs.
3. If proc B is then re-added to the LP, its threads are sharing VPAs
with proc A briefly as they come online.
As the hypervisor may check for the VPA's yield_count field oddity, it
may detect an unexpected value and kill the LPAR.
Suggested-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
Reviewed-by: Nathan Lynch <nathanl@linux.ibm.com>
[mpe: s/cpu_present_map/cpu_present_mask/ in change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221114160150.13554-1-ldufour@linux.ibm.com
Signed-off-by: Mamatha Inamdar minamdar@redhat.com