spapr_numa.c: handle auto NUMA node with no distance info

numa_complete_configuration() in hw/core/numa.c always adds a NUMA node
for the pSeries machine if none was specified, but without node distance
information for the single node created.

NUMA FORM1 affinity code didn't rely on numa_state information to do its
job, but FORM2 does. As is now, this is the result of a pSeries guest
with NUMA FORM2 affinity when no NUMA nodes is specified:

$ numactl -H
available: 1 nodes (0)
node 0 cpus: 0
node 0 size: 16222 MB
node 0 free: 15681 MB
No distance information available.

This can be amended in spapr_numa_FORM2_write_rtas_tables(). We're
enforcing that the local distance (the distance to the node to itself) is
always 10. This allows for the proper creation of the NUMA distance tables,
fixing the output of 'numactl -H' in the guest:

$ numactl -H
available: 1 nodes (0)
node 0 cpus: 0
node 0 size: 16222 MB
node 0 free: 15685 MB
node distances:
node   0
  0:  10

CC: Igor Mammedov <[email protected]>
Reviewed-by: Greg Kurz <[email protected]>
Signed-off-by: Daniel Henrique Barboza <[email protected]>
Message-Id: <[email protected]>
Acked-by: Igor Mammedov <[email protected]>
Signed-off-by: David Gibson <[email protected]>

hw/ppc/spapr_numa.c

@@ -539,6 +539,17 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
 
     for (src = 0; src < nb_numa_nodes; src++) {
         for (dst = 0; dst < nb_numa_nodes; dst++) {
+            /*
+             * We need to be explicit with the local distance
+             * value to cover the case where the user didn't added any
+             * NUMA nodes, but QEMU adds the default NUMA node without
+             * adding the numa_info to retrieve distance info from.
+             */
+            if (src == dst) {
+                node_distances[i++] = 10;
+                continue;
+            }
+
             node_distances[i++] = numa_info[src].distance[dst];
         }
     }