[PATCH] hw/mem/pc-dimm: Hint it is not usable on non-NUMA machines

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

When trying to use the pc-dimm device on a non-NUMA machine, we get:

  $ qemu-system-arm -M none -cpu max -S -device pc-dimm
  Segmentation fault (core dumped)

  (gdb) bt
  #0  pc_dimm_realize (dev=0x555556da3e90, errp=0x7fffffffcd10) at hw/mem/pc-dimm.c:184
  #1  0x0000555555fe1f8f in device_set_realized (obj=0x555556da3e90, value=true, errp=0x7fffffffce18) at hw/core/qdev.c:761
  #2  0x0000555555feb4a9 in property_set_bool (obj=0x555556da3e90, v=0x555556e54420, name=0x5555563c3c41 "realized", opaque=0x555556a704f0, errp=0x7fffffffce18) at qom/object.c:2257

Use a friendler error message instead:

  $ qemu-system-arm -M none -cpu max -S -device pc-dimm
  qemu-system-arm: -device pc-dimm: NUMA is not supported by this machine-type

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 hw/mem/pc-dimm.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/hw/mem/pc-dimm.c b/hw/mem/pc-dimm.c
index a3a2560301c..e8851a0c3b1 100644
--- a/hw/mem/pc-dimm.c
+++ b/hw/mem/pc-dimm.c
@@ -181,8 +181,13 @@ static void pc_dimm_realize(DeviceState *dev, Error **errp)
     PCDIMMDevice *dimm = PC_DIMM(dev);
     PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(dimm);
     MachineState *ms = MACHINE(qdev_get_machine());
-    int nb_numa_nodes = ms->numa_state->num_nodes;
+    int nb_numa_nodes;
 
+    if (!ms->numa_state) {
+        error_setg(errp, "NUMA is not supported by this machine-type");
+        return;
+    }
+    nb_numa_nodes = ms->numa_state->num_nodes;
     if (!dimm->hostmem) {
         error_setg(errp, "'" PC_DIMM_MEMDEV_PROP "' property is not set");
         return;
-- 
2.26.3