[PATCH v5 COLOPre 08/18] tools/libxl: introduce libxl__domain_restore_device_model to load qemu state

[Wen Congyang <wency@cn.fujitsu.com>]

From: Yang Hongyang <hongyang.yang@easystack.cn>

In normal migration, the qemu state was passed to qemu as a parameter.
With COLO, Secondary vm is running. So we will do the following steps
at every checkpoint:
1. suspend both primary vm and secondary vm
2. sync the state
3. resume both primary vm and secondary vm
Primary will send qemu's state in step2, and
Secondary's qemu should read it and restore the state before it
is resumed. We can not pass the state to qemu as a parameter because
Secondary QEMU already started at this point, so we introduce
libxl__domain_restore_device_model() to do it.
This API should be called before resuming secondary vm.

Signed-off-by: Yang Hongyang <hongyang.yang@easystack.cn>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Cc: Anthony Perard <anthony.perard@citrix.com>
---
 tools/libxl/libxl_dom_save.c | 20 ++++++++++++++++++++
 tools/libxl/libxl_internal.h |  4 ++++
 tools/libxl/libxl_qmp.c      | 10 ++++++++++
 3 files changed, 34 insertions(+)

diff --git a/tools/libxl/libxl_dom_save.c b/tools/libxl/libxl_dom_save.c
index 0bfa5fc..88cb1b3 100644
--- a/tools/libxl/libxl_dom_save.c
+++ b/tools/libxl/libxl_dom_save.c
@@ -609,6 +609,26 @@ int libxl__restore_emulator_xenstore_data(libxl__domain_create_state *dcs,
     return rc;
 }
 
+int libxl__domain_restore_device_model(libxl__gc *gc, uint32_t domid,
+                                       const char *restore_file)
+{
+    int rc;
+
+    switch (libxl__device_model_version_running(gc, domid)) {
+    case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL:
+        /* not supported now */
+        rc = ERROR_INVAL;
+        break;
+    case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN:
+        rc = libxl__qmp_restore(gc, domid, restore_file);
+        break;
+    default:
+        rc = ERROR_INVAL;
+    }
+
+    return rc;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 9470d96..27a4590 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1115,6 +1115,8 @@ _hidden int libxl__domain_rename(libxl__gc *gc, uint32_t domid,
                                  const char *old_name, const char *new_name,
                                  xs_transaction_t trans);
 
+_hidden int libxl__domain_restore_device_model(libxl__gc *gc, uint32_t domid,
+                                               const char *restore_file);
 _hidden int libxl__domain_resume_device_model(libxl__gc *gc, uint32_t domid);
 
 _hidden const char *libxl__userdata_path(libxl__gc *gc, uint32_t domid,
@@ -1758,6 +1760,8 @@ _hidden int libxl__qmp_stop(libxl__gc *gc, int domid);
 _hidden int libxl__qmp_resume(libxl__gc *gc, int domid);
 /* Save current QEMU state into fd. */
 _hidden int libxl__qmp_save(libxl__gc *gc, int domid, const char *filename);
+/* Load current QEMU state from fd. */
+_hidden int libxl__qmp_restore(libxl__gc *gc, int domid, const char *filename);
 /* Set dirty bitmap logging status */
 _hidden int libxl__qmp_set_global_dirty_log(libxl__gc *gc, int domid, bool enable);
 _hidden int libxl__qmp_insert_cdrom(libxl__gc *gc, int domid, const libxl_device_disk *disk);
diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
index 714038b..eec8a44 100644
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -905,6 +905,16 @@ int libxl__qmp_save(libxl__gc *gc, int domid, const char *filename)
                            NULL, NULL);
 }
 
+int libxl__qmp_restore(libxl__gc *gc, int domid, const char *state_file)
+{
+    libxl__json_object *args = NULL;
+
+    qmp_parameters_add_string(gc, &args, "filename", state_file);
+
+    return qmp_run_command(gc, domid, "xen-load-devices-state", args,
+                           NULL, NULL);
+}
+
 static int qmp_change(libxl__gc *gc, libxl__qmp_handler *qmp,
                       char *device, char *target, char *arg)
 {
-- 
2.5.0