diff --git a/include/block/snapshot.h b/include/block/snapshot.h
index 940345692f..cda82c1ba1 100644
--- a/include/block/snapshot.h
+++ b/include/block/snapshot.h
@@ -45,6 +45,13 @@ typedef struct QEMUSnapshotInfo {
     uint64_t icount; /* record/replay step */
 } QEMUSnapshotInfo;
 
+/*
+ * Global state (GS) API. These functions run under the BQL lock.
+ *
+ * See include/block/block-global-state.h for more information about
+ * the GS API.
+ */
+
 int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
                        const char *name);
 bool bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs,
@@ -73,9 +80,11 @@ int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs,
                                          Error **errp);
 
 
-/* Group operations. All block drivers are involved.
+/*
+ * Group operations. All block drivers are involved.
  * These functions will properly handle dataplane (take aio_context_acquire
- * when appropriate for appropriate block drivers */
+ * when appropriate for appropriate block drivers
+ */
 
 bool bdrv_all_can_snapshot(bool has_devices, strList *devices,
                            Error **errp);
diff --git a/block/snapshot.c b/block/snapshot.c
index ccacda8bd5..3dd3c9d3bd 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -57,6 +57,8 @@ int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
     QEMUSnapshotInfo *sn_tab, *sn;
     int nb_sns, i, ret;
 
+    assert(qemu_in_main_thread());
+
     ret = -ENOENT;
     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
     if (nb_sns < 0) {
@@ -105,6 +107,7 @@ bool bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs,
     bool ret = false;
 
     assert(id || name);
+    assert(qemu_in_main_thread());
 
     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
     if (nb_sns < 0) {
@@ -200,6 +203,7 @@ static BlockDriverState *bdrv_snapshot_fallback(BlockDriverState *bs)
 int bdrv_can_snapshot(BlockDriverState *bs)
 {
     BlockDriver *drv = bs->drv;
+    assert(qemu_in_main_thread());
     if (!drv || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
         return 0;
     }
@@ -220,6 +224,9 @@ int bdrv_snapshot_create(BlockDriverState *bs,
 {
     BlockDriver *drv = bs->drv;
     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
+
+    assert(qemu_in_main_thread());
+
     if (!drv) {
         return -ENOMEDIUM;
     }
@@ -240,6 +247,8 @@ int bdrv_snapshot_goto(BlockDriverState *bs,
     BdrvChild **fallback_ptr;
     int ret, open_ret;
 
+    assert(qemu_in_main_thread());
+
     if (!drv) {
         error_setg(errp, "Block driver is closed");
         return -ENOMEDIUM;
@@ -348,6 +357,8 @@ int bdrv_snapshot_delete(BlockDriverState *bs,
     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
     int ret;
 
+    assert(qemu_in_main_thread());
+
     if (!drv) {
         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs));
         return -ENOMEDIUM;
@@ -380,6 +391,8 @@ int bdrv_snapshot_list(BlockDriverState *bs,
 {
     BlockDriver *drv = bs->drv;
     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
+
+    assert(qemu_in_main_thread());
     if (!drv) {
         return -ENOMEDIUM;
     }
@@ -419,6 +432,8 @@ int bdrv_snapshot_load_tmp(BlockDriverState *bs,
 {
     BlockDriver *drv = bs->drv;
 
+    assert(qemu_in_main_thread());
+
     if (!drv) {
         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs));
         return -ENOMEDIUM;
@@ -447,6 +462,8 @@ int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs,
     int ret;
     Error *local_err = NULL;
 
+    assert(qemu_in_main_thread());
+
     ret = bdrv_snapshot_load_tmp(bs, id_or_name, NULL, &local_err);
     if (ret == -ENOENT || ret == -EINVAL) {
         error_free(local_err);
@@ -515,6 +532,8 @@ bool bdrv_all_can_snapshot(bool has_devices, strList *devices,
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
 
+    assert(qemu_in_main_thread());
+
     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
         return false;
     }
@@ -549,6 +568,8 @@ int bdrv_all_delete_snapshot(const char *name,
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
 
+    assert(qemu_in_main_thread());
+
     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
         return -1;
     }
@@ -588,6 +609,8 @@ int bdrv_all_goto_snapshot(const char *name,
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
 
+    assert(qemu_in_main_thread());
+
     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
         return -1;
     }
@@ -622,6 +645,8 @@ int bdrv_all_has_snapshot(const char *name,
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
 
+    assert(qemu_in_main_thread());
+
     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
         return -1;
     }
@@ -663,6 +688,7 @@ int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
 {
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
+    assert(qemu_in_main_thread());
 
     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
         return -1;
@@ -703,6 +729,8 @@ BlockDriverState *bdrv_all_find_vmstate_bs(const char *vmstate_bs,
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
 
+    assert(qemu_in_main_thread());
+
     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
         return NULL;
     }
diff --git a/migration/savevm.c b/migration/savevm.c
index d59e976d50..d4bc226caa 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2786,6 +2786,8 @@ bool save_snapshot(const char *name, bool overwrite, const char *vmstate,
     g_autoptr(GDateTime) now = g_date_time_new_now_local();
     AioContext *aio_context;
 
+    assert(qemu_in_main_thread());
+
     if (migration_is_blocked(errp)) {
         return false;
     }
