From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>

qemu_loadvm_load_state_buffer() and its load_state_buffer
SaveVMHandler allow providing device state buffer to explicitly
specified device via its idstr and instance id.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
---
 include/migration/register.h | 15 +++++++++++++++
 migration/savevm.c           | 23 +++++++++++++++++++++++
 migration/savevm.h           |  3 +++
 3 files changed, 41 insertions(+)

diff --git a/include/migration/register.h b/include/migration/register.h
index ff0faf5f68c8..58891aa54b76 100644
--- a/include/migration/register.h
+++ b/include/migration/register.h
@@ -229,6 +229,21 @@ typedef struct SaveVMHandlers {
      */
     int (*load_state)(QEMUFile *f, void *opaque, int version_id);
 
+    /**
+     * @load_state_buffer (invoked outside the BQL)
+     *
+     * Load device state buffer provided to qemu_loadvm_load_state_buffer().
+     *
+     * @opaque: data pointer passed to register_savevm_live()
+     * @buf: the data buffer to load
+     * @len: the data length in buffer
+     * @errp: pointer to Error*, to store an error if it happens.
+     *
+     * Returns true to indicate success and false for errors.
+     */
+    bool (*load_state_buffer)(void *opaque, char *buf, size_t len,
+                              Error **errp);
+
     /**
      * @load_setup
      *
diff --git a/migration/savevm.c b/migration/savevm.c
index faebf47ef51f..7c1aa8ad7b9d 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -3060,6 +3060,29 @@ int qemu_loadvm_approve_switchover(void)
     return migrate_send_rp_switchover_ack(mis);
 }
 
+bool qemu_loadvm_load_state_buffer(const char *idstr, uint32_t instance_id,
+                                   char *buf, size_t len, Error **errp)
+{
+    SaveStateEntry *se;
+
+    se = find_se(idstr, instance_id);
+    if (!se) {
+        error_setg(errp,
+                   "Unknown idstr %s or instance id %u for load state buffer",
+                   idstr, instance_id);
+        return false;
+    }
+
+    if (!se->ops || !se->ops->load_state_buffer) {
+        error_setg(errp,
+                   "idstr %s / instance %u has no load state buffer operation",
+                   idstr, instance_id);
+        return false;
+    }
+
+    return se->ops->load_state_buffer(se->opaque, buf, len, errp);
+}
+
 bool save_snapshot(const char *name, bool overwrite, const char *vmstate,
                   bool has_devices, strList *devices, Error **errp)
 {
diff --git a/migration/savevm.h b/migration/savevm.h
index 58f871a7ed9c..cb58434a9437 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -71,4 +71,7 @@ int qemu_loadvm_approve_switchover(void);
 int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
         bool in_postcopy);
 
+bool qemu_loadvm_load_state_buffer(const char *idstr, uint32_t instance_id,
+                                   char *buf, size_t len, Error **errp);
+
 #endif