qemu: Delete USB devices used by domain on stop

To prevent assigning one USB device to two domains,
we keep a list of assigned USB devices. On domain
startup - qemuProcessStart() - we insert devices
used by domain into the list but remove them only
on detach-device. Devices are, however, released
on qemuProcessStop() as well.
(cherry picked from commit e2f5dd6134ebeb6846450c7d7782273d3d274859)

src/qemu/qemu_hostdev.c

@@ -755,6 +755,63 @@ void qemuDomainReAttachHostdevDevices(struct qemud_driver *driver,
     pciDeviceListFree(pcidevs);
 }
 
+static void
+qemuDomainReAttachHostUsbDevices(struct qemud_driver *driver,
+                                 const char *name,
+                                 virDomainHostdevDefPtr *hostdevs,
+                                 int nhostdevs)
+{
+    int i;
+
+    for (i = 0; i < nhostdevs; i++) {
+        virDomainHostdevDefPtr hostdev = hostdevs[i];
+        usbDevice *usb, *tmp;
+        const char *used_by = NULL;
+
+        if (hostdev->mode != VIR_DOMAIN_HOSTDEV_MODE_SUBSYS)
+            continue;
+        if (hostdev->source.subsys.type != VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_USB)
+            continue;
+
+        usb = usbGetDevice(hostdev->source.subsys.u.usb.bus,
+                           hostdev->source.subsys.u.usb.device);
+
+        if (!usb) {
+            VIR_WARN("Unable to reattach USB device %03d.%03d on domain %s",
+                     hostdev->source.subsys.u.usb.bus,
+                     hostdev->source.subsys.u.usb.device,
+                     name);
+            continue;
+        }
+
+        /* Delete only those USB devices which belongs
+         * to domain @name because qemuProcessStart() might
+         * have failed because USB device is already taken.
+         * Therefore we want to steal only those devices from
+         * the list which were taken by @name */
+
+        tmp = usbDeviceListFind(driver->activeUsbHostdevs, usb);
+        usbFreeDevice(usb);
+
+        if (!tmp) {
+            VIR_WARN("Unable to find device %03d.%03d "
+                     "in list of active USB devices",
+                     hostdev->source.subsys.u.usb.bus,
+                     hostdev->source.subsys.u.usb.device);
+            continue;
+        }
+
+        used_by = usbDeviceGetUsedBy(tmp);
+        if (STREQ_NULLABLE(used_by, name)) {
+            VIR_DEBUG("Removing %03d.%03d dom=%s from activeUsbHostdevs",
+                      hostdev->source.subsys.u.usb.bus,
+                      hostdev->source.subsys.u.usb.device,
+                      name);
+
+            usbDeviceListDel(driver->activeUsbHostdevs, tmp);
+        }
+    }
+}
 
 void qemuDomainReAttachHostDevices(struct qemud_driver *driver,
                                    virDomainDefPtr def)
@@ -764,4 +821,7 @@ void qemuDomainReAttachHostDevices(struct qemud_driver *driver,
 
     qemuDomainReAttachHostdevDevices(driver, def->name, def->hostdevs,
                                      def->nhostdevs);
+
+    qemuDomainReAttachHostUsbDevices(driver, def->name, def->hostdevs,
+                                     def->nhostdevs);
 }