libxl_qmp: Tell QEMU about live migration or snapshot

Since version 2.10, QEMU will lock the disk images so a second QEMU
instance will not try to open it. This would prevent live migration from
working correctly. A new parameter as been added to the QMP command
"xen-save-devices-state" in QEMU version 2.11 which allow to unlock the
disk image for a live migration, but also keep it locked for a snapshot.

QEMU commit: 5d6c599fe1d69a1bf8c5c4d3c58be2b31cd625ad
"migration, xen: Fix block image lock issue on live migration"

The extra "live" parameter can only be use if QEMU knows about it, so
only add it if qemu is recent enough.

The struct libxl__domain_suspend_state as now knowledge if the suspend
is part of a live migration.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

diff --git a/tools/libxl/libxl_dom_save.c b/tools/libxl/libxl_dom_save.c
index 64876722771c5401a814df918cca9ef816921b6c..2e9ec4dbf2427fb67a116a8b0fb930a1657148fb 100644 (file)
--- a/tools/libxl/libxl_dom_save.c
+++ b/tools/libxl/libxl_dom_save.c
@@ -361,6 +361,7 @@ void libxl__domain_save(libxl__egc *egc, libxl__domain_save_state *dss)
 
     dsps->ao = ao;
     dsps->domid = domid;
+    dsps->live = !!live;
     rc = libxl__domain_suspend_init(egc, dsps, type);
     if (rc) goto out;
 

diff --git a/tools/libxl/libxl_dom_suspend.c b/tools/libxl/libxl_dom_suspend.c
index ca411074129a14c7f355d868cec608f56333ea1d..1e904bae8a3eae8f7bfa56cb0be0e783de8707de 100644 (file)
--- a/tools/libxl/libxl_dom_suspend.c
+++ b/tools/libxl/libxl_dom_suspend.c
@@ -86,7 +86,7 @@ int libxl__domain_suspend_device_model(libxl__gc *gc,
         if (libxl__qmp_stop(gc, domid))
             return ERROR_FAIL;
         /* Save DM state into filename */
-        ret = libxl__qmp_save(gc, domid, filename);
+        ret = libxl__qmp_save(gc, domid, filename, dsps->live);
         if (ret)
             unlink(filename);
         break;

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 506687fbe9b3c8ba8ef145db23d17bd47fda8d93..8dd63319fc3602d02f9638776845bce42c22a3b5 100644 (file)
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1822,7 +1822,8 @@ _hidden int libxl__qmp_stop(libxl__gc *gc, int domid);
 /* Resume QEMU. */
 _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);
+_hidden int libxl__qmp_save(libxl__gc *gc, int domid, const char *filename,
+                            bool live);
 /* Load current QEMU state from file. */
 _hidden int libxl__qmp_restore(libxl__gc *gc, int domid, const char *filename);
 /* Set dirty bitmap logging status */
@@ -3264,6 +3265,7 @@ struct libxl__domain_suspend_state {
     /* set by caller of libxl__domain_suspend_init */
     libxl__ao *ao;
     uint32_t domid;
+    bool live;
 
     /* private */
     libxl_domain_type type;

diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
index b1c6598cf7da1c684ec6de36e2a6f1fdf120d930..d03cb51668f606730fe27a37e6a011e862beeba4 100644 (file)
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -350,7 +350,6 @@ static int qmp_handle_response(libxl__gc *gc, libxl__qmp_handler *qmp,
     return 0;
 }
 
-#if 0
 static bool qmp_qemu_check_version(libxl__qmp_handler *qmp, int major,
                                    int minor, int micro)
 {
@@ -359,7 +358,6 @@ static bool qmp_qemu_check_version(libxl__qmp_handler *qmp, int major,
             (qmp->version.minor > minor ||
              (qmp->version.minor == minor && qmp->version.micro >= micro)));
 }
-#endif
 
 /*
  * Handler functions
@@ -942,13 +940,27 @@ int libxl__qmp_system_wakeup(libxl__gc *gc, int domid)
     return qmp_run_command(gc, domid, "system_wakeup", NULL, NULL, NULL);
 }
 
-int libxl__qmp_save(libxl__gc *gc, int domid, const char *filename)
+int libxl__qmp_save(libxl__gc *gc, int domid, const char *filename, bool live)
 {
     libxl__json_object *args = NULL;
+    libxl__qmp_handler *qmp = NULL;
+    int rc;
+
+    qmp = libxl__qmp_initialize(gc, domid);
+    if (!qmp)
+        return ERROR_FAIL;
 
     qmp_parameters_add_string(gc, &args, "filename", (char *)filename);
-    return qmp_run_command(gc, domid, "xen-save-devices-state", args,
-                           NULL, NULL);
+
+    /* live parameter was added to QEMU 2.11. It signal QEMU that the save
+     * operation is for a live migration rather that for taking a snapshot. */
+    if (qmp_qemu_check_version(qmp, 2, 11, 0))
+        qmp_parameters_add_bool(gc, &args, "live", live);
+
+    rc = qmp_synchronous_send(qmp, "xen-save-devices-state", args,
+                              NULL, NULL, qmp->timeout);
+    libxl__qmp_close(qmp);
+    return rc;
 }
 
 int libxl__qmp_restore(libxl__gc *gc, int domid, const char *state_file)