tools/libxl: introduction of libxl__qmp_restore to load qemu state

In normal migration, the qemu state is 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 is already started
at this point, so we introduce libxl__qmp_restore() to do it.

Signed-off-by: Yang Hongyang <hongyang.yang@easystack.cn>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Changlong Xie <xiecl.fnst@cn.fujitsu.com>
Cc: Anthony Perard <anthony.perard@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 345a764d7e29d2868196a1e4aae37b95f9cb88b2..fc3426a8ebf66054d318794ac6c44f0b0a64a3d9 100644 (file)
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1765,6 +1765,8 @@ _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 file. */
+_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 c45702e60b5f9014b0cef55ff02ba97c7d81f47f..c0bdfcb83a340eff6ac212baf482edcf81b6525f 100644 (file)
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -906,6 +906,16 @@ 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)
 {