[Xen-devel] [PATCH v10 01/31] tools/libxl: introduce libxl__domain_restore_device_model to load qemu state

[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 already started
at this point, so we introduce libxl__domain_restore_device_model() to
do it. This API MUST be called before resuming secondary vm.

Signed-off-by: Yang Hongyang <hongyang.yang@xxxxxxxxxxxx>
Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 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 4eb7960..7d345f9 100644
--- a/tools/libxl/libxl_dom_save.c
+++ b/tools/libxl/libxl_dom_save.c
@@ -512,6 +512,26 @@ 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:
+        /* Will never be supported. */
+        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 a1aae97..5320e5e 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1119,6 +1119,8 @@ _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,
@@ -1762,6 +1764,8 @@ _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 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




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