[Qemu-devel] [RFC PATCH] ppc/spapr: support sparse NUMA node numbering

[Nishanth Aravamudan <nacc@linux.vnet.ibm.com>]

With generic sparse NUMA node parsing in place ("numa: enable sparse
node numbering"), ppc can be updated to iterate over only the
user-specified nodes.

qemu-system-ppc64 -machine pseries,accel=kvm,usb=off -m 4096
-realtime mlock=off -numa node,nodeid=3 -numa node,nodeid=2 -smp 4

Before:

info numa:
node 0 cpus: 0 2
node 0 size: 2048 MB
node 1 cpus: 1 3
node 1 size: 2048 MB

numactl --hardware:
available: 2 nodes (0-1)
node 0 cpus: 0 2
node 0 size: 2027 MB
node 0 free: 1875 MB
node 1 cpus: 1 3
node 1 size: 2045 MB
node 1 free: 1980 MB
node distances:
node   0   1
  0:  10  40
  1:  40  10

After:

info numa:
node 2 cpus: 0 2
node 2 size: 2048 MB
node 3 cpus: 1 3
node 3 size: 2048 MB

numactl --hardware:
available: 3 nodes (0,2-3)
node 0 cpus:
node 0 size: 0 MB
node 0 free: 0 MB
node 2 cpus: 0 2
node 2 size: 2027 MB
node 2 free: 1943 MB
node 3 cpus: 1 3
node 3 size: 2045 MB
node 3 free: 1904 MB
node distances:
node   0   2   3
  0:  10  40  40
  2:  40  10  40
  3:  40  40  10

Note, the empty node 0 is due to the Linux kernel.

Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 82f183f..d07857a 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -707,7 +707,10 @@ static int spapr_populate_memory(sPAPREnvironment *spapr, void *fdt)
 
     /* RAM: Node 1 and beyond */
     mem_start = node0_size;
-    for (i = 1; i < nb_numa_nodes; i++) {
+    for (i = 1; i < max_numa_node; i++) {
+        if (!numa_info[i].present) {
+            continue;
+        }
         mem_reg_property[0] = cpu_to_be64(mem_start);
         if (mem_start >= ram_size) {
             node_size = 0;