testscript: Add a test for PCI BDF assignment

The added test checks that libvirt and CHV assigned and propagate PCI
BDF correctly to the guest's PCI devices. It furthermore ensures, that
these assignment stay valid even after live migration

Signed-off-by: Pascal Scholz <pascal.scholz@cyberus-technology.de>
On-behalf-of: SAP pascal.scholz@sap.com

Author: scholzp

tests/testscript.py

@@ -1246,10 +1246,70 @@ def test_live_migration_with_vcpu_pinning(self):
         assert int(taskset_vcpu0_controller, 16) == int(taskset_vcpu0_compute, 16)
         assert int(taskset_vcpu2_controller, 16) == int(taskset_vcpu2_compute, 16)
 
+    def test_bdf_assignment(self):
+        """
+        Test if all BDFs are correctly assigned in different scenarios:
+            1) After VM creation and hotplugging a device
+            2) If a devices is removed and it's BDF reused
+            3) Two devices that use the same BDF (expected to fail)
+            4) After live migration (all devices retain assigned BDFs)
+        """
+
+        VIRTIO_NETWORK_DEVICE = "1af4:1041"
+        VIRTIO_BLOCK_DEVICE = "1af4:1042"
+        VIRTIO_ENTROPY_SOURCE = "1af4:1044"
+
+        """
+        1) All BDFs are correctly assigned (with precedence for XML assignments)
+
+        In the current implementation, CHV and libvirt will instantiate
+        disk devices before net devices (because currently we hotplug
+        them). The VM's XML only assigns a BDF to the net device. If
+        libvirt would miss to order assignment, this subtlety would
+        create a conflict where both try to acquire BDF 00:02.0. This
+        should be prevented by reserving all BDFs that are assigned to
+        devices in the XML before assigning one to each device. This is
+        implicitly tested in case 1.
+        """
+        controllerVM.succeed("virsh define /etc/domain-chv.xml")
+        controllerVM.succeed("virsh start testvm")
+        controllerVM.succeed("virsh attach-device testvm /etc/new_interface.xml")
+
+        assert wait_for_ssh(controllerVM)
+
+        devices_before = pci_devices_by_bdf(controllerVM)
+        assert devices_before["00:01.0"] == VIRTIO_ENTROPY_SOURCE
+        assert devices_before["00:02.0"] == VIRTIO_NETWORK_DEVICE
+        assert devices_before["00:03.0"] == VIRTIO_BLOCK_DEVICE
+        assert devices_before["00:0c.0"] == VIRTIO_NETWORK_DEVICE
+
+        # 2) Check that BDF is freed and can be reallocated when de-/attaching a (entirely different) device
+        controllerVM.succeed("virsh detach-device testvm /etc/new_interface.xml")
+        assert pci_devices_by_bdf(controllerVM).get("00:0c.0") == None
+        controllerVM.succeed(
+            "virsh attach-disk --domain testvm --target vdb --persistent --source /var/lib/libvirt/storage-pools/nfs-share/cirros.img --address pci:0.0.c.0"
+        )
+        devices_before_livemig = pci_devices_by_bdf(controllerVM)
+        assert devices_before_livemig.get("00:0c.0") == VIRTIO_BLOCK_DEVICE
+
+        # 3) Adding to the same bdf twice fails
+        controllerVM.wait_until_fails(
+            "virsh attach-device testvm /etc/new_interface.xml"
+        )
+
+        # 4) Check that BDFs stay the same after migration
+        controllerVM.succeed(
+            "virsh migrate --domain testvm --desturi ch+tcp://computeVM/session --persistent --live --p2p"
+        )
+        assert wait_for_ssh(computeVM)
+        devices_after_livemig = pci_devices_by_bdf(computeVM)
+        assert devices_before_livemig == devices_after_livemig
+
 
 def suite():
     # Test cases in alphabetical order
     testcases = [
+        LibvirtTests.test_bdf_assignment,
         LibvirtTests.test_disk_is_locked,
         LibvirtTests.test_disk_resize_qcow2,
         LibvirtTests.test_disk_resize_raw,