1 files changed, 39 insertions, 1 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index 0b6377332c..18ece99c6e 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -61,6 +61,7 @@ struct BlockBackend {
 
     uint64_t perm;
     uint64_t shared_perm;
+    bool disable_perm;
 
     bool allow_write_beyond_eof;
 
@@ -578,7 +579,7 @@ int blk_set_perm(BlockBackend *blk, uint64_t perm, uint64_t shared_perm,
 {
     int ret;
 
-    if (blk->root) {
+    if (blk->root && !blk->disable_perm) {
         ret = bdrv_child_try_set_perm(blk->root, perm, shared_perm, errp);
         if (ret < 0) {
             return ret;
@@ -597,15 +598,52 @@ void blk_get_perm(BlockBackend *blk, uint64_t *perm, uint64_t *shared_perm)
     *shared_perm = blk->shared_perm;
 }
 
+/*
+ * Notifies the user of all BlockBackends that migration has completed. qdev
+ * devices can tighten their permissions in response (specifically revoke
+ * shared write permissions that we needed for storage migration).
+ *
+ * If an error is returned, the VM cannot be allowed to be resumed.
+ */
+void blk_resume_after_migration(Error **errp)
+{
+    BlockBackend *blk;
+    Error *local_err = NULL;
+
+    for (blk = blk_all_next(NULL); blk; blk = blk_all_next(blk)) {
+        if (!blk->disable_perm) {
+            continue;
+        }
+
+        blk->disable_perm = false;
+
+        blk_set_perm(blk, blk->perm, blk->shared_perm, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            blk->disable_perm = true;
+            return;
+        }
+    }
+}
+
 static int blk_do_attach_dev(BlockBackend *blk, void *dev)
 {
     if (blk->dev) {
         return -EBUSY;
     }
+
+    /* While migration is still incoming, we don't need to apply the
+     * permissions of guest device BlockBackends. We might still have a block
+     * job or NBD server writing to the image for storage migration. */
+    if (runstate_check(RUN_STATE_INMIGRATE)) {
+        blk->disable_perm = true;
+    }
+
     blk_ref(blk);
     blk->dev = dev;
     blk->legacy_dev = false;
     blk_iostatus_reset(blk);
+
     return 0;
 }