[Xen-devel] [RFC Patch v4 2/8] tools: libxl: introduce a new API libxl__domain_restore() to read qemu state

[Wen Congyang <wency@xxxxxxxxxxxxxx>]

Secondary vm is running in colo mode. So we will do
the following things again and again:
1. suspend both primay vm and secondary vm
2. sync the state
3. resume both primary vm and secondary vm
We will send qemu's state each time in step2, and
slave's qemu should read it each time before resuming
secondary vm. Introduce a new API libxl__domain_restore()
to do it. This API should be called before resuming
secondary vm.

Note: we should update qemu to support it.
Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
---
 tools/libxl/libxl.c          | 18 ++++++++++++++++++
 tools/libxl/libxl_dom.c      | 26 ++++++++++++++++++++++++++
 tools/libxl/libxl_internal.h |  4 ++++
 tools/libxl/libxl_qmp.c      | 10 ++++++++++
 4 files changed, 58 insertions(+)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 18561fb..255b13f 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -476,6 +476,24 @@ int libxl_domain_rename(libxl_ctx *ctx, uint32_t domid,
     return rc;
 }
 
+int libxl__domain_restore(libxl__gc *gc, uint32_t domid)
+{
+    int rc = 0;
+
+    libxl_domain_type type = libxl__domain_type(gc, domid);
+    if (type != LIBXL_DOMAIN_TYPE_HVM) {
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    rc = libxl__domain_restore_device_model(gc, domid);
+    if (rc)
+        LOG(ERROR, "failed to restore device mode for domain %u:%d",
+            domid, rc);
+out:
+    return rc;
+}
+
 int libxl__domain_resume(libxl__gc *gc, uint32_t domid, int suspend_cancel)
 {
     int rc = 0;
diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index ada2ada..9e3662c 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -1176,6 +1176,32 @@ int libxl__domain_suspend_device_model(libxl__gc *gc,
     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 */
+        return ERROR_FAIL;
+    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);
+        return rc;
+    default:
+        return ERROR_INVAL;
+    }
+}
+
 int libxl__domain_resume_device_model(libxl__gc *gc, uint32_t domid)
 {
 
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index f5f2648..7706816 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -994,6 +994,7 @@ _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,
@@ -1011,6 +1012,7 @@ _hidden int libxl__userdata_store(libxl__gc *gc, uint32_t 
domid,
                                   const char *userdata_userid,
                                   const uint8_t *data, int datalen);
 
+_hidden int libxl__domain_restore(libxl__gc *gc, uint32_t domid);
 _hidden int libxl__domain_resume(libxl__gc *gc, uint32_t domid,
                                  int suspend_cancel);
 
@@ -1607,6 +1609,8 @@ _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 c7324e6..e1c2fd1 100644
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -871,6 +871,16 @@ 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", (char *)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)
 {
-- 
1.9.3


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