powerpc/numa: Set numa_node for all possible cpus

A Powerpc system with multiple possible nodes and with CONFIG_NUMA
enabled always used to have a node 0, even if node 0 does not any cpus
or memory attached to it. As per PAPR, node affinity of a cpu is only
available once its present / online. For all cpus that are possible but
not present, cpu_to_node() would point to node 0.

To ensure a cpuless, memoryless dummy node is not online, powerpc need
to make sure all possible but not present cpu_to_node are set to a
proper node.

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200818081104.57888-2-srikar@linux.vnet.ibm.com

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 5ddc83b..f63e1a4 100644 (file)
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -507,6 +507,11 @@ static int numa_setup_cpu(unsigned long lcpu)
        int fcpu = cpu_first_thread_sibling(lcpu);
        int nid = NUMA_NO_NODE;
 
+       if (!cpu_present(lcpu)) {
+               set_cpu_numa_node(lcpu, first_online_node);
+               return first_online_node;
+       }
+
        /*
         * If a valid cpu-to-node mapping is already available, use it
         * directly instead of querying the firmware, since it represents
@@ -944,8 +949,17 @@ void __init mem_topology_setup(void)
 
        reset_numa_cpu_lookup_table();
 
-       for_each_present_cpu(cpu)
+       for_each_possible_cpu(cpu) {
+               /*
+                * Powerpc with CONFIG_NUMA always used to have a node 0,
+                * even if it was memoryless or cpuless. For all cpus that
+                * are possible but not present, cpu_to_node() would point
+                * to node 0. To remove a cpuless, memoryless dummy node,
+                * powerpc need to make sure all possible but not present
+                * cpu_to_node are set to a proper node.
+                */
                numa_setup_cpu(cpu);
+       }
 }
 
 void __init initmem_init(void)