Retain boot device selection upon boot image change

When changing boot image in libvirt domain, note current boot
device and restore it if the image being changed resides on
the active boot device.

Prior to this patch, as a side-effect of changing boot image,
boot device selection could get reset.

Change-Id: Ic848882acbd446effbdf9b761d4ac1025d24c324

releasenotes/notes/fix-retain-boot-device-5ae02731d2a000d3.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixes situation when changing boot image could invalidate current boot
+    device selection. The fix is to note current libvirt boot device and restore
+    it if the image being changed resides on the active boot device.

sushy_tools/emulator/resources/systems/libvirtdriver.py

@@ -990,11 +990,14 @@ class LibvirtDriver(AbstractSystemsDriver):
 
         self._remove_boot_images(domain, domain_tree, device)
 
-        if boot_image:
+        boot_device = None
 
+        if boot_image:
             self._add_boot_image(domain, domain_tree, device,
                                  boot_image, write_protected)
 
+            boot_device = self.get_boot_device(identity)
+
         with libvirt_open(self._uri) as conn:
             xml = ET.tostring(domain_tree)
 
@@ -1009,6 +1012,9 @@ class LibvirtDriver(AbstractSystemsDriver):
 
                 raise error.FishyError(msg)
 
+        if device == boot_device:
+            self.set_boot_device(identity, boot_device)
+
     def _find_device_by_path(self, vol_path):
         """Get device attributes using path
 

sushy_tools/tests/unit/emulator/resources/systems/test_libvirt.py

@@ -512,7 +512,11 @@ class LibvirtDriverTestCase(base.BaseTestCase):
 
         with mock.patch.object(
                 self.test_driver, 'get_power_state', return_value='Off'):
-            self.test_driver.set_boot_image(self.uuid, 'Cd', '/tmp/image.iso')
+            with mock.patch.object(
+                    self.test_driver, 'get_boot_device', return_value=None):
+
+                self.test_driver.set_boot_image(
+                    self.uuid, 'Cd', '/tmp/image.iso')
 
         conn_mock = libvirt_rw_mock.return_value
         pool_mock.listAllVolumes.assert_called_once_with()
@@ -524,6 +528,39 @@ class LibvirtDriverTestCase(base.BaseTestCase):
 
         conn_mock.defineXML.assert_called_once_with(mock.ANY)
 
+    @mock.patch('libvirt.open', autospec=True)
+    @mock.patch('libvirt.openReadOnly', autospec=True)
+    @mock.patch(
+        'sushy_tools.emulator.resources.systems.libvirtdriver.LibvirtDriver'
+        '.get_power_state', new=mock.MagicMock(return_value='Off'))
+    @mock.patch(
+        'sushy_tools.emulator.resources.systems.libvirtdriver.LibvirtDriver'
+        '.get_boot_device', return_value='Cd')
+    @mock.patch(
+        'sushy_tools.emulator.resources.systems.libvirtdriver.LibvirtDriver'
+        '.set_boot_device')
+    @mock.patch(
+        'sushy_tools.emulator.resources.systems.libvirtdriver.LibvirtDriver'
+        '._add_boot_image', new=mock.MagicMock())
+    @mock.patch(
+        'sushy_tools.emulator.resources.systems.libvirtdriver.LibvirtDriver'
+        '._remove_boot_images', new=mock.MagicMock())
+    def test_set_boot_image_restore_boot_device(
+            self, sbd_mock, gbd_mock, libvirt_mock, libvirt_rw_mock):
+
+        with open('sushy_tools/tests/unit/emulator/domain.xml', 'r') as f:
+            data = f.read()
+
+        conn_mock = libvirt_rw_mock.return_value
+        domain_mock = conn_mock.lookupByUUID.return_value
+        domain_mock.XMLDesc.return_value = data
+
+        self.test_driver.set_boot_image(
+            self.uuid, 'Cd', '/tmp/image.iso')
+
+        gbd_mock.assert_called_once_with(self.uuid)
+        sbd_mock.assert_called_once_with(self.uuid, 'Cd')
+
     @mock.patch('libvirt.openReadOnly', autospec=True)
     def test_get_total_memory(self, libvirt_mock):
         conn_mock = libvirt_mock.return_value