After e492dc5a267e "pci: Eliminate pci_find_primary_bus()" we don't
have an easy mean to retrieve the primary bus of a machine. This will be
needed by virtio-iommu-device which is bound to be dynamically instantiated
in at least ARM virt and Q35 machines.

Adding a get_primary_pci_bus() callback allows to retrieve the PCIBus the
iommu is connected to.

Signed-off-by: Eric Auger <>


This is a temporary solution until we decide whether the
virtio-iommu-device should be instantiable through a -device command
line or through a machine command line, as already suggested by Peter
(for vsmmuv3 though).
 include/hw/boards.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/hw/boards.h b/include/hw/boards.h
index efb0a9e..0ed376a 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -156,6 +156,8 @@ typedef struct {
  *    should instead use "unimplemented-device" for all memory ranges where
  *    the guest will attempt to probe for a device that QEMU doesn't
  *    implement and a stub device is required.
+ * @get_primary_pci_bus: return the primary PCI bus or NULL if there are
+ *    several root buses
 struct MachineClass {
     /*< private >*/
@@ -212,6 +214,7 @@ struct MachineClass {
                                                          unsigned cpu_index);
     const CPUArchIdList *(*possible_cpu_arch_ids)(MachineState *machine);
     int64_t (*get_default_cpu_node_id)(const MachineState *ms, int idx);
+    PCIBus *(*get_primary_pci_bus)(const MachineState *ms);

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