Re: [Xen-devel] [PATCH v2] libxl: fix migration of PV and PVH domUs with and without qemu

[Olaf Hering <olaf@xxxxxxxxx>]

Am Fri, 3 May 2019 17:29:53 +0200
schrieb Roger Pau Monné <roger.pau@xxxxxxxxxx>:

> On Fri, May 03, 2019 at 04:11:32PM +0200, Olaf Hering wrote:
> > Am Fri, 3 May 2019 13:04:11 +0200
> > schrieb Roger Pau Monné <roger.pau@xxxxxxxxxx>:
> >   
> > > Wouldn't it be easier to leave libxl__need_xenpv_qemu alone and just
> > > use the contents of the migration stream to decide whether to launch a
> > > QEMU for the PV backends or not? ie: just parsing the domain config on
> > > the migration stream should be enough for the destination side to
> > > decide whether a QEMU is needed in order to handle the PV backends?  
> > 
> > I think that is done anyway. How would the receiving side know what to do?  
> 
> Hm, OK. I will wait for v3 with the domid stuff fixed.

I think it will be as simple as this. In the end b_info.device_model_version
must be set prior the call to store_libxl_entry.

--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -92,9 +92,6 @@ int libxl__domain_build_info_setdefault(
             } else {
                 b_info->device_model_version = libxl__default_device_model(gc);
             }
-        } else {
-            b_info->device_model_version =
-                LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN;
         }
         if (b_info->device_model_version
                 == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {
@@ -969,6 +966,18 @@ static void initiate_domain_create(libxl
     dcs->sdss.dm.guest_domid = 0; /* means we haven't spawned */
 
     /*
+     * libxl__domain_build_info_setdefault sets this only for HVM
+     * set it before store_libxl_entry()
+     */
+    if (d_config->b_info.device_model_version
+        == LIBXL_DEVICE_MODEL_VERSION_UNKNOWN) {
+        ret = libxl__need_xenpv_qemu(gc, d_config);
+        if (ret > 0)
+            d_config->b_info.device_model_version =
+                LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN;
+    }
+
+    /*
      * Set the dm version quite early so that libxl doesn't have to pass the
      * build info around just to know if the domain has a device model or not.
      */
--- a/tools/libxl/libxl_dom_suspend.c
+++ b/tools/libxl/libxl_dom_suspend.c
@@ -377,7 +377,9 @@ static void domain_suspend_common_guest_
     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,
         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);

Olaf

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