[PATCH RFC 17/26] migration: Add qemu_loadvm_load_state_buffer() and its handler

["Maciej S. Szmigiero" <mail@maciej.szmigiero.name>]

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.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
---
 include/migration/register.h | 15 +++++++++++++++
 migration/savevm.c           | 25 +++++++++++++++++++++++++
 migration/savevm.h           |  3 +++
 3 files changed, 43 insertions(+)

diff --git a/include/migration/register.h b/include/migration/register.h
index 9d36e35bd612..7d29b7e0b559 100644
--- a/include/migration/register.h
+++ b/include/migration/register.h
@@ -257,6 +257,21 @@ typedef struct SaveVMHandlers {
      */
     int (*load_state)(QEMUFile *f, void *opaque, int version_id);
 
+    /**
+     * @load_state_buffer
+     *
+     * Load device state buffer provided to qemu_loadvm_load_state_buffer().
+     *
+     * @opaque: data pointer passed to register_savevm_live()
+     * @data: the data buffer to load
+     * @data_size: the data length in buffer
+     * @errp: pointer to Error*, to store an error if it happens.
+     *
+     * Returns zero to indicate success and negative for error
+     */
+    int (*load_state_buffer)(void *opaque, char *data, size_t data_size,
+                             Error **errp);
+
     /**
      * @load_setup
      *
diff --git a/migration/savevm.c b/migration/savevm.c
index fa35504678bf..2e4d63faca06 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -3073,6 +3073,31 @@ int qemu_loadvm_approve_switchover(void)
     return migrate_send_rp_switchover_ack(mis);
 }
 
+int 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 -1;
+    }
+
+    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 -1;
+    }
+
+    if (se->ops->load_state_buffer(se->opaque, buf, len, errp) != 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
 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 74669733dd63..c879ba8c970e 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -70,4 +70,7 @@ int qemu_loadvm_approve_switchover(void);
 int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
         bool in_postcopy, bool inactivate_disks);
 
+int qemu_loadvm_load_state_buffer(const char *idstr, uint32_t instance_id,
+                                  char *buf, size_t len, Error **errp);
+
 #endif