1 files changed, 28 insertions, 7 deletions

diff --git a/chardev/char.c b/chardev/char.c
index 75993f903f..398f09df19 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -39,6 +39,7 @@
 #include "qemu/option.h"
 #include "qemu/id.h"
 #include "qemu/coroutine.h"
+#include "qemu/yank.h"
 
 #include "chardev-internal.h"
 
@@ -266,6 +267,7 @@ static void char_init(Object *obj)
 {
     Chardev *chr = CHARDEV(obj);
 
+    chr->handover_yank_instance = false;
     chr->logfd = -1;
     qemu_mutex_init(&chr->chr_write_lock);
 
@@ -959,6 +961,7 @@ void qemu_chr_set_feature(Chardev *chr,
 static Chardev *chardev_new(const char *id, const char *typename,
                             ChardevBackend *backend,
                             GMainContext *gcontext,
+                            bool handover_yank_instance,
                             Error **errp)
 {
     Object *obj;
@@ -971,6 +974,7 @@ static Chardev *chardev_new(const char *id, const char *typename,
 
     obj = object_new(typename);
     chr = CHARDEV(obj);
+    chr->handover_yank_instance = handover_yank_instance;
     chr->label = g_strdup(id);
     chr->gcontext = gcontext;
 
@@ -1004,7 +1008,7 @@ Chardev *qemu_chardev_new(const char *id, const char *typename,
         id = genid;
     }
 
-    chr = chardev_new(id, typename, backend, gcontext, errp);
+    chr = chardev_new(id, typename, backend, gcontext, false, errp);
     if (!chr) {
         return NULL;
     }
@@ -1032,7 +1036,7 @@ ChardevReturn *qmp_chardev_add(const char *id, ChardevBackend *backend,
     }
 
     chr = chardev_new(id, object_class_get_name(OBJECT_CLASS(cc)),
-                      backend, NULL, errp);
+                      backend, NULL, false, errp);
     if (!chr) {
         return NULL;
     }
@@ -1057,9 +1061,10 @@ ChardevReturn *qmp_chardev_change(const char *id, ChardevBackend *backend,
                                   Error **errp)
 {
     CharBackend *be;
-    const ChardevClass *cc;
+    const ChardevClass *cc, *cc_new;
     Chardev *chr, *chr_new;
     bool closed_sent = false;
+    bool handover_yank_instance;
     ChardevReturn *ret;
 
     chr = qemu_chr_find(id);
@@ -1091,13 +1096,20 @@ ChardevReturn *qmp_chardev_change(const char *id, ChardevBackend *backend,
         return NULL;
     }
 
-    cc = char_get_class(ChardevBackendKind_str(backend->type), errp);
-    if (!cc) {
+    cc = CHARDEV_GET_CLASS(chr);
+    cc_new = char_get_class(ChardevBackendKind_str(backend->type), errp);
+    if (!cc_new) {
         return NULL;
     }
 
-    chr_new = chardev_new(id, object_class_get_name(OBJECT_CLASS(cc)),
-                          backend, chr->gcontext, errp);
+    /*
+     * The new chardev should not register a yank instance if the current
+     * chardev has registered one already.
+     */
+    handover_yank_instance = cc->supports_yank && cc_new->supports_yank;
+
+    chr_new = chardev_new(id, object_class_get_name(OBJECT_CLASS(cc_new)),
+                          backend, chr->gcontext, handover_yank_instance, errp);
     if (!chr_new) {
         return NULL;
     }
@@ -1121,6 +1133,15 @@ ChardevReturn *qmp_chardev_change(const char *id, ChardevBackend *backend,
         return NULL;
     }
 
+    /* change successfull, clean up */
+    chr_new->handover_yank_instance = false;
+
+    /*
+     * When the old chardev is freed, it should not unregister the yank
+     * instance if the new chardev needs it.
+     */
+    chr->handover_yank_instance = handover_yank_instance;
+
     object_unparent(OBJECT(chr));
     object_property_add_child(get_chardevs_root(), chr_new->label,
                               OBJECT(chr_new));