vfio/iommufd: device name blocker

If an invariant device name cannot be created, block CPR.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Link: https://lore.kernel.org/qemu-devel/1751493538-202042-12-git-send-email-steven.sistare@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/device.c

@@ -28,6 +28,8 @@
 #include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "qemu/units.h"
+#include "migration/cpr.h"
+#include "migration/blocker.h"
 #include "monitor/monitor.h"
 #include "vfio-helpers.h"
 
@@ -324,8 +326,16 @@ bool vfio_device_get_name(VFIODevice *vbasedev, Error **errp)
             } else {
                 /*
                  * Assign a name so any function printing it will not break.
+                 * The fd number changes across processes, so this cannot be
+                 * used as an invariant name for CPR.
                  */
                 vbasedev->name = g_strdup_printf("VFIO_FD%d", vbasedev->fd);
+                error_setg(&vbasedev->cpr.id_blocker,
+                           "vfio device with fd=%d needs an id property",
+                           vbasedev->fd);
+                return migrate_add_blocker_modes(&vbasedev->cpr.id_blocker,
+                                                 errp, MIG_MODE_CPR_TRANSFER,
+                                                 -1) == 0;
             }
         }
     }
@@ -336,6 +346,7 @@ bool vfio_device_get_name(VFIODevice *vbasedev, Error **errp)
 void vfio_device_free_name(VFIODevice *vbasedev)
 {
     g_clear_pointer(&vbasedev->name, g_free);
+    migrate_del_blocker(&vbasedev->cpr.id_blocker);
 }
 
 void vfio_device_set_fd(VFIODevice *vbasedev, const char *str, Error **errp)

include/hw/vfio/vfio-cpr.h

@@ -30,6 +30,7 @@ typedef struct VFIOContainerCPR {
 
 typedef struct VFIODeviceCPR {
     Error *mdev_blocker;
+    Error *id_blocker;
 } VFIODeviceCPR;
 
 bool vfio_legacy_cpr_register_container(struct VFIOContainer *container,