When cores are added while the system is running in a lower SMT mode,
some threads of those cores remain offline. Moving the system to a
higher SMT mode later fails to online those threads.
For example, on a system with four cores:
1. ppc64_cpu --smt=off
2. nproc
expected: 4
3. ppc64_cpu --smt
expected/actual: "SMT is off"
4. drmgr -c cpu -a -q 4
5. ppc64_cpu --smt
expected/actual: "SMT is off"
6. ppc64_cpu --smt=8
7. ppc64_cpu --smt
expected: SMT=8
actual: SMT=1: 4-7; SMT=8: 0-3
8. nproc
expected: 64
actual: 36
Post commit d1099e2276df ("powerpc/pseries: Honour current SMT state
when DLPAR onlining CPUs"), when new CPUs are added, the CPU-to-node
mapping is currently updated only for CPUs that are immediately onlined.
CPUs that are made present but remain offline due to the current SMT
mode therefore do not get a CPU-to-node mapping.
When those CPUs are subsequently onlined after switching to a higher
SMT mode, the online operation fails because the required CPU-to-node
mapping is missing.
Update the CPU-to-node mapping before applying the SMT restrictions so
that all newly present CPUs have a node mapping, including CPUs that
remain offline in the current SMT mode.
Fixes: d1099e2276df ("powerpc/pseries: Honour current SMT state when DLPAR
onlining CPUs")
Reported-by: Samir Mulani <[email protected]>
Signed-off-by: Srikar Dronamraju <[email protected]>
---
arch/powerpc/platforms/pseries/hotplug-cpu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c
b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index bc6926dbf148..b5dc942eec63 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -402,6 +402,7 @@ static int dlpar_online_cpu(struct device_node *dn)
if (get_hard_smp_processor_id(cpu) != thread)
continue;
+ find_and_update_cpu_nid(cpu);
if (!topology_is_primary_thread(cpu)) {
if (cpu_smt_control != CPU_SMT_ENABLED)
break;
@@ -410,7 +411,6 @@ static int dlpar_online_cpu(struct device_node *dn)
}
cpu_maps_update_done();
- find_and_update_cpu_nid(cpu);
rc = device_online(get_cpu_device(cpu));
if (rc) {
dlpar_offline_cpu(dn);
--
2.43.7
