libxl: fix migration of PV and PVH domUs with and without qemu

If a domU has a qemu-xen instance attached, it is required to call qemus
"xen-save-devices-state" method. Without it, the receiving side of a PV or
PVH migration may be unable to lock the image:

xen be: qdisk-51712: xen be: qdisk-51712: error: Failed to get "write" lock
error: Failed to get "write" lock
xen be: qdisk-51712: xen be: qdisk-51712: initialise() failed
initialise() failed

To fix this bug, libxl__domain_suspend_device_model() and
libxl__domain_resume_device_model() have to be called not only for HVM,
but also if the active device_model is QEMU_XEN.

Unfortunately, libxl__domain_build_info_setdefault() used to hardcode
b_info->device_model_version to QEMU_XEN if it does not know it any
better. As a result libxl__device_model_version_running() will return
incorrect values. This breaks domUs without a device_model.
libxl__qmp_stop() would wait 10 seconds in qmp_open() for a qemu that
will never appear. During this long timeframe the domU remains in state
paused on the sending side. As a result network connections may be
dropped. Once this bug is fixed as well, by just removing the assumption
that every domU has a QEMU_XEN, there is no code to actually initialise
b_info->device_model_version.

There is a helper function libxl__need_xenpv_qemu(), which is used in
various places to decide if a device_model has to be spawned. This
function can not be used as is, just to fill device_model_version,
because store_libxl_entry() was already called earlier.

Introduce LIBXL_DEVICE_MODEL_VERSION_NONE for PV and PVH that have no
need for a device_model to make the state explicit. Indicate this new
state via LIBXL_HAVE macro in libxl.h.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Cc: Roger Pau Monné <roger.pau@citrix.com>
Cc: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 482499a6c057b78ac12b39f1f8bd05079e16980d..e0f6916b6651acb86fdc4f6158de108c3bd85585 100644 (file)
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -1182,6 +1182,13 @@ void libxl_mac_copy(libxl_ctx *ctx, libxl_mac *dst, const libxl_mac *src);
  */
 #define LIBXL_HAVE_PVCALLS 1
 
+/*
+ * LIBXL_HAVE_DEVICE_MODEL_VERSION_NONE
+ *
+ * If this is defined, libxl will only run a device-model if required.
+ */
+#define LIBXL_HAVE_DEVICE_MODEL_VERSION_NONE 1
+
 typedef char **libxl_string_list;
 void libxl_string_list_dispose(libxl_string_list *sl);
 int libxl_string_list_length(const libxl_string_list *sl);

diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 3f0431cc8447332bb020d4788c7c5d7012251bdc..64336b0d29118cd5fc526e5eb847203b01f21bde 100644 (file)
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -47,9 +47,20 @@ int libxl__domain_set_device_model(libxl__gc *gc, libxl_domain_config *d_config)
         }
         break;
     default:
-        b_info->device_model_version =
-            LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL;
-        break;
+        ret = libxl__need_xenpv_qemu(gc, d_config);
+        switch (ret) {
+        case 1:
+            d_config->b_info.device_model_version =
+                LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN;
+            break;
+        case 0:
+            d_config->b_info.device_model_version =
+                LIBXL_DEVICE_MODEL_VERSION_NONE;
+            break;
+        default:
+            LOGE(ERROR, "Unable to determine QEMU requisite");
+            return ret;
+        }
     }
 
     if (b_info->device_model_version == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {

diff --git a/tools/libxl/libxl_dom_suspend.c b/tools/libxl/libxl_dom_suspend.c
index d1af3a65730387ee32be4dcaa70fb096cae9bacb..c492fe5dd107914714e74f0683aaa270710c2015 100644 (file)
--- a/tools/libxl/libxl_dom_suspend.c
+++ b/tools/libxl/libxl_dom_suspend.c
@@ -379,7 +379,9 @@ static void domain_suspend_common_guest_suspended(libxl__egc *egc,
     libxl__ev_xswatch_deregister(gc, &dsps->guest_watch);
     libxl__ev_time_deregister(gc, &dsps->guest_timeout);
 
-    if (dsps->type == LIBXL_DOMAIN_TYPE_HVM) {
+    if (dsps->type == LIBXL_DOMAIN_TYPE_HVM ||
+        libxl__device_model_version_running(gc, dsps->domid) ==
+        LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {
         dsps->callback_device_model_done = domain_suspend_common_done;
         libxl__domain_suspend_device_model(egc, dsps); /* must be last */
         return;
@@ -459,7 +461,9 @@ int libxl__domain_resume(libxl__gc *gc, uint32_t domid, int suspend_cancel)
         goto out;
     }
 
-    if (type == LIBXL_DOMAIN_TYPE_HVM) {
+    if (type == LIBXL_DOMAIN_TYPE_HVM ||
+        libxl__device_model_version_running(gc, domid) ==
+        LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {
         rc = libxl__domain_resume_device_model(gc, domid);
         if (rc) {
             LOGD(ERROR, domid, "failed to resume device model:%d", rc);

diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index cb4702fd7a56707bb825d0f7a9e1253eeabc3c3b..75bde095bc37fdd14d57fdb0c87c314b5b0d7aba 100644 (file)
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -106,6 +106,7 @@ libxl_device_model_version = Enumeration("device_model_version", [
     (0, "UNKNOWN"),
     (1, "QEMU_XEN_TRADITIONAL"), # Historical qemu-xen device model (qemu-dm)
     (2, "QEMU_XEN"),             # Upstream based qemu-xen device model
+    (3, "NONE"),
     ])
 
 libxl_console_type = Enumeration("console_type", [