hw/pxb: Add a bypass iommu property

Add a bypass_iommu property for pci_expander_bridge, the property
is used to indicate whether pxb root bus will bypass iommu. By
default the bypass_iommu is disabled, and it can be enabled with:
qemu -device pxb-pcie,bus_nr=0x10,addr=0x1,bypass_iommu=true

Signed-off-by: Xingang Wang <wangxingang5@huawei.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <1625748919-52456-3-git-send-email-wangxingang5@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/pci-bridge/pci_expander_bridge.c

@@ -57,6 +57,7 @@ struct PXBDev {
 
     uint8_t bus_nr;
     uint16_t numa_node;
+    bool bypass_iommu;
 };
 
 static PXBDev *convert_to_pxb(PCIDevice *dev)
@@ -255,6 +256,7 @@ static void pxb_dev_realize_common(PCIDevice *dev, bool pcie, Error **errp)
     bus->map_irq = pxb_map_irq_fn;
 
     PCI_HOST_BRIDGE(ds)->bus = bus;
+    PCI_HOST_BRIDGE(ds)->bypass_iommu = pxb->bypass_iommu;
 
     pxb_register_bus(dev, bus, &local_err);
     if (local_err) {
@@ -301,6 +303,7 @@ static Property pxb_dev_properties[] = {
     /* Note: 0 is not a legal PXB bus number. */
     DEFINE_PROP_UINT8("bus_nr", PXBDev, bus_nr, 0),
     DEFINE_PROP_UINT16("numa_node", PXBDev, numa_node, NUMA_NODE_UNASSIGNED),
+    DEFINE_PROP_BOOL("bypass_iommu", PXBDev, bypass_iommu, false),
     DEFINE_PROP_END_OF_LIST(),
 };