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[Xen-devel] [PATCH v11 01/27] tools/libxl: introduction of libxl__qmp_restore to load qemu state

From: Wen Congyang <wency@xxxxxxxxxxxxxx>

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@xxxxxxxxxxxx>
Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
Signed-off-by: Changlong Xie <xiecl.fnst@xxxxxxxxxxxxxx>
Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
 tools/libxl/libxl_internal.h |  2 ++
 tools/libxl/libxl_qmp.c      | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 005fe53..7801385 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1762,6 +1762,8 @@ _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 
 _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 c45702e..c0bdfcb 100644
--- 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 
                            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)

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