[PATCH v2 1/2] numa: Set default distance map if needed

[Gavin Shan <gshan@redhat.com>]

The following option is used to specify the distance map. It's
possible the option isn't provided by user. In this case, the
distance map isn't populated and exposed to platform. On the
other hand, the empty NUMA node, where no memory resides, is
allowed on ARM64 virt platform. For these empty NUMA nodes,
their corresponding device-tree nodes aren't populated, but
their NUMA IDs should be included in the "/distance-map"
device-tree node, so that kernel can probe them properly if
device-tree is used.

  -numa,dist,src=<numa_id>,dst=<numa_id>,val=<distance>

So when user doesn't specify distance map, we need to generate
the default distance map, where the local and remote distances
are 10 and 20 separately. However, this is going to change the
hardware description of the guest in this particular scenario.
It's fine as the guest should be tolerant to ignore the distance
map completely or parse it properly by following the device-tree
specification.

This introduces an extra parameter to the exiting function
complete_init_numa_distance() to generate the default distance
map when no node pair distances are provided by user.

Signed-off-by: Gavin Shan <gshan@redhat.com>
---
 hw/core/numa.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/hw/core/numa.c b/hw/core/numa.c
index 510d096a88..c508d857a0 100644
--- a/hw/core/numa.c
+++ b/hw/core/numa.c
@@ -594,7 +594,7 @@ static void validate_numa_distance(MachineState *ms)
     }
 }
 
-static void complete_init_numa_distance(MachineState *ms)
+static void complete_init_numa_distance(MachineState *ms, bool is_default)
 {
     int src, dst;
     NodeInfo *numa_info = ms->numa_state->nodes;
@@ -609,6 +609,8 @@ static void complete_init_numa_distance(MachineState *ms)
             if (numa_info[src].distance[dst] == 0) {
                 if (src == dst) {
                     numa_info[src].distance[dst] = NUMA_DISTANCE_MIN;
+                } else if (is_default) {
+                    numa_info[src].distance[dst] = NUMA_DISTANCE_DEFAULT;
                 } else {
                     numa_info[src].distance[dst] = numa_info[dst].distance[src];
                 }
@@ -716,13 +718,20 @@ void numa_complete_configuration(MachineState *ms)
          * A->B != distance B->A, then that means the distance table is
          * asymmetric. In this case, the distances for both directions
          * of all node pairs are required.
+         *
+         * The default node pair distances, which are 10 and 20 for the
+         * local and remote nodes separately, are provided if user doesn't
+         * specify any node pair distances.
          */
         if (ms->numa_state->have_numa_distance) {
             /* Validate enough NUMA distance information was provided. */
             validate_numa_distance(ms);
 
             /* Validation succeeded, now fill in any missing distances. */
-            complete_init_numa_distance(ms);
+            complete_init_numa_distance(ms, false);
+        } else {
+            complete_init_numa_distance(ms, true);
+            ms->numa_state->have_numa_distance = true;
         }
     }
 }
-- 
2.23.0