Re: [PATCH v12 1/7] s390x/cpu topology: Creating CPU topology device

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On 12/1/22 10:08, Thomas Huth wrote:
On 29/11/2022 18.42, Pierre Morel wrote:
We will need a Topology device to transfer the topology
during migration and to implement machine reset.

The device creation is fenced by s390_has_topology().

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
...
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 2e64ffab45..973bbdd36e 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -44,6 +44,7 @@
  #include "hw/s390x/pv.h"
  #include "migration/blocker.h"
  #include "qapi/visitor.h"
+#include "hw/s390x/cpu-topology.h"
  static Error *pv_mig_blocker;
@@ -102,6 +103,24 @@ static void s390_init_cpus(MachineState *machine)
      }
  }
+static DeviceState *s390_init_topology(MachineState *machine, Error **errp)
+{
+    DeviceState *dev;
+
+    dev = qdev_new(TYPE_S390_CPU_TOPOLOGY);
+
+    object_property_add_child(&machine->parent_obj,
+                              TYPE_S390_CPU_TOPOLOGY, OBJECT(dev));
+    object_property_set_int(OBJECT(dev), "num-cores",
+                            machine->smp.cores * machine->smp.threads, errp);

I wonder what will happen if we ever support multithreading on s390x later? ... won't this cause some oddities when migrating older machines types with smp.threads > 1 later? Maybe we should prohibit to enable the CPU topology instead if a user tried to use threads > 1 with an older machine type?

Yes, right, I forgot to change this back.
Anyway it has no sens for new machine which prohibit smp.threads > 1 neither.

I change this by returning an error in case we have smp.threads > 1

Thanks.

Pierre


  Thomas


+    object_property_set_int(OBJECT(dev), "num-sockets",
+                            machine->smp.sockets, errp);
+
+    sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), errp);
+
+    return dev;
+}


--
Pierre Morel
IBM Lab Boeblingen



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