hw/virtio/virtio-iommu-pci: Enforce the device is plugged on the root…

… bus

In theory the virtio-iommu-pci could be plugged anywhere in the PCIe
topology and as long as the dt/acpi info are properly built this should
work. However at the moment we fail to do that because the
virtio-iommu-pci BDF is not computed at plug time and in that case
vms->virtio_iommu_bdf gets an incorrect value.

For instance if the virtio-iommu-pci is plugged onto a pcie root port
and the virtio-iommu protects a virtio-block-pci device the guest does
not boot.

So let's do not pretend we do support this case and fail the initialize()
if we detect the virtio-iommu-pci is plugged anywhere else than on the
root bus. Anyway this ability is not needed.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <20221012163448.121368-1-eric.auger@redhat.com>
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Tested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/virtio/virtio-iommu-pci.c

@@ -17,6 +17,7 @@
 #include "hw/qdev-properties-system.h"
 #include "qapi/error.h"
 #include "hw/boards.h"
+#include "hw/pci/pci_bus.h"
 #include "qom/object.h"
 
 typedef struct VirtIOIOMMUPCI VirtIOIOMMUPCI;
@@ -44,6 +45,7 @@ static Property virtio_iommu_pci_properties[] = {
 static void virtio_iommu_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
 {
     VirtIOIOMMUPCI *dev = VIRTIO_IOMMU_PCI(vpci_dev);
+    PCIBus *pbus = pci_get_bus(&vpci_dev->pci_dev);
     DeviceState *vdev = DEVICE(&dev->vdev);
     VirtIOIOMMU *s = VIRTIO_IOMMU(vdev);
 
@@ -57,11 +59,17 @@ static void virtio_iommu_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
             s->reserved_regions[i].type != VIRTIO_IOMMU_RESV_MEM_T_MSI) {
             error_setg(errp, "reserved region %d has an invalid type", i);
             error_append_hint(errp, "Valid values are 0 and 1\n");
+            return;
         }
     }
+    if (!pci_bus_is_root(pbus)) {
+        error_setg(errp, "virtio-iommu-pci must be plugged on the root bus");
+        return;
+    }
+
     object_property_set_link(OBJECT(dev), "primary-bus",
-                             OBJECT(pci_get_bus(&vpci_dev->pci_dev)),
-                             &error_abort);
+                             OBJECT(pbus), &error_abort);
+
     virtio_pci_force_virtio_1(vpci_dev);
     qdev_realize(vdev, BUS(&vpci_dev->bus), errp);
 }