[Xen-devel] [PATCH v4 --for 4.6 COLOPre 14/25] tools/libxl: introduce libxl__domain_restore_device_model to load qemu state

[Yang Hongyang <yanghy@xxxxxxxxxxxxxx>]

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 primay 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 <yanghy@xxxxxxxxxxxxxx>
Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>
---
 tools/libxl/libxl_dom_save.c | 29 +++++++++++++++++++++++++++++
 tools/libxl/libxl_internal.h |  3 +++
 tools/libxl/libxl_qmp.c      | 10 ++++++++++
 3 files changed, 42 insertions(+)

diff --git a/tools/libxl/libxl_dom_save.c b/tools/libxl/libxl_dom_save.c
index f89f5d4..0926b71 100644
--- a/tools/libxl/libxl_dom_save.c
+++ b/tools/libxl/libxl_dom_save.c
@@ -675,6 +675,35 @@ out:
     return ret;
 }
 
+int libxl__domain_restore_device_model(libxl__gc *gc, uint32_t domid)
+{
+    char *state_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:
+        /*
+         * This function may be called too many times for the same gc,
+         * so we use NOGC, and free the memory before return to avoid
+         * OOM.
+         */
+        state_file = libxl__sprintf(NOGC,
+                                    XC_DEVICE_MODEL_RESTORE_FILE".%d",
+                                    domid);
+        rc = libxl__qmp_restore(gc, domid, state_file);
+        free(state_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 0eb5f41..fb777c1 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1074,6 +1074,7 @@ _hidden int libxl__domain_rename(libxl__gc *gc, uint32_t 
domid,
 
 _hidden int libxl__toolstack_restore(uint32_t domid, const uint8_t *buf,
                                      uint32_t size, void *data);
+_hidden int libxl__domain_restore_device_model(libxl__gc *gc, uint32_t domid);
 _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,
@@ -1702,6 +1703,8 @@ _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 6484f5e..080cb9f 100644
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -904,6 +904,16 @@ 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)
 {
-- 
1.9.1


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel