[PATCH v1] libxl: always call qemus xen-save-devices-state in suspend/resume

[Olaf Hering <olaf@aepfle.de>]

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
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

The proper way to decide if a PV or PVH domU has a qemu-xen running is
to use the libxl__need_xenpv_qemu API. But since there is no copy of a
libxl_domain_config available in these places, it should be enough to
check if xenstore contains the relevant info.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
---
 tools/libxl/libxl_dom_suspend.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/libxl/libxl_dom_suspend.c b/tools/libxl/libxl_dom_suspend.c
index 1e904bae8a..0d769eefd8 100644
--- a/tools/libxl/libxl_dom_suspend.c
+++ b/tools/libxl/libxl_dom_suspend.c
@@ -377,7 +377,9 @@ 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) {
         rc = libxl__domain_suspend_device_model(gc, dsps);
         if (rc) {
             LOGD(ERROR, dsps->domid,
@@ -460,7 +462,9 @@ 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);

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