hw/arm/sbsa-ref: Use two-stage SMMU

Now that our SMMU model supports enabling both stages of translation
at once, we can enable this in the sbsa-ref board.  Existing guest
code that only programs stage 1 and doesn't care about stage 2 should
continue to run with the same behaviour, but guests that do want to
do nested SMMU configurations can now do so.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>
Message-id: 20240816161350.3706332-5-peter.maydell@linaro.org

hw/arm/sbsa-ref.c

@@ -621,6 +621,7 @@ static void create_smmu(const SBSAMachineState *sms, PCIBus *bus)
 
     dev = qdev_new(TYPE_ARM_SMMUV3);
 
+    object_property_set_str(OBJECT(dev), "stage", "nested", &error_abort);
     object_property_set_link(OBJECT(dev), "primary-bus", OBJECT(bus),
                              &error_abort);
     sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);