Re: [PATCH v2 3/4] net/virtio: avoid passing NULL to qdev_set_parent_bus

[Jens Freimann]

On Wed, Nov 20, 2019 at 10:04:01AM -0500, Michael S. Tsirkin wrote:

On Wed, Nov 20, 2019 at 03:38:58PM +0100, Jens Freimann wrote:

Make sure we don't pass NULL to qdev_set_parent_bus(). Also simplify
code a bit and fix a typo.
This fixes CID 1407224.

Fixes: 9711cd0dfc3f ("net/virtio: add failover support")
Signed-off-by: Jens Freimann <jfreim...@redhat.com>

patch itself is ok I think

Reviewed-by: Michael S. Tsirkin <m...@redhat.com>

but some questions on the commit log

---
 hw/net/virtio-net.c | 42 +++++++++++++++++++++++++-----------------
 1 file changed, 25 insertions(+), 17 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index ac4d19109e..78f1e4e87c 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -2805,25 +2805,33 @@ static bool failover_replug_primary(VirtIONet *n, Error 
**errp)
         n->primary_device_opts = qemu_opts_from_qdict(
                 qemu_find_opts("device"),
                 n->primary_device_dict, errp);
-    }
-    if (n->primary_device_opts) {
-        if (n->primary_dev) {
-            n->primary_bus = n->primary_dev->parent_bus;
-        }
-        qdev_set_parent_bus(n->primary_dev, n->primary_bus);
-        n->primary_should_be_hidden = false;
-        qemu_opt_set_bool(n->primary_device_opts,
-                "partially_hotplugged", true, errp);
-        hotplug_ctrl = qdev_get_hotplug_handler(n->primary_dev);
-        if (hotplug_ctrl) {
-            hotplug_handler_pre_plug(hotplug_ctrl, n->primary_dev, errp);
-            hotplug_handler_plug(hotplug_ctrl, n->primary_dev, errp);
+        if (!n->primary_device_opts) {
+            error_setg(errp, "virtio_net: couldn't find primary device opts");
+            goto out;
         }
-        if (!n->primary_dev) {
+    }
+    if (!n->primary_dev) {
             error_setg(errp, "virtio_net: couldn't find primary device");
-        }
+            goto out;
     }
-    return *errp != NULL;
+
+    n->primary_bus = n->primary_dev->parent_bus;
+    if (!n->primary_bus) {
+        error_setg(errp, "virtio_net: couldn't find primary bus");
+        goto out;
+    }
+    qdev_set_parent_bus(n->primary_dev, n->primary_bus);
+    n->primary_should_be_hidden = false;
+    qemu_opt_set_bool(n->primary_device_opts,
+                      "partially_hotplugged", true, errp);
+    hotplug_ctrl = qdev_get_hotplug_handler(n->primary_dev);
+    if (hotplug_ctrl) {
+        hotplug_handler_pre_plug(hotplug_ctrl, n->primary_dev, errp);
+        hotplug_handler_plug(hotplug_ctrl, n->primary_dev, errp);
+    }
+
+out:
+    return *errp == NULL;
 }

 static void virtio_net_handle_migration_primary(VirtIONet *n,

So the logic actually was inverted here? Then ... how did this work?
and how was it tested?

It did not work and I missed the error in my test output. I tested it
now manually by migrating and then cancelling. Device was added back
to source VM successfully.

Will sent new version with better patch description.

Thanks!

regards
Jens