[PATCH-for-5.2 v2] hw/virtio/vhost-backend: Fix Coverity CID 1432871

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Fix uninitialized value issues reported by Coverity:

  Field 'msg.reserved' is uninitialized when calling write().

While the 'struct vhost_msg' does not have a 'reserved' field,
we still initialize it to have the two parts of the function
consistent.

Reported-by: Coverity (CID 1432864: UNINIT)
Fixes: c471ad0e9bd ("vhost_net: device IOTLB support")
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
v2: comment 'struct vhost_msg' is also initialized (Peter)
---
 hw/virtio/vhost-backend.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
index 88c8ecc9e03..222bbcc62de 100644
--- a/hw/virtio/vhost-backend.c
+++ b/hw/virtio/vhost-backend.c
@@ -257,7 +257,7 @@ static int vhost_kernel_send_device_iotlb_msg(struct vhost_dev *dev,
                                               struct vhost_iotlb_msg *imsg)
 {
     if (dev->backend_cap & (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2)) {
-        struct vhost_msg_v2 msg;
+        struct vhost_msg_v2 msg = {};
 
         msg.type = VHOST_IOTLB_MSG_V2;
         msg.iotlb = *imsg;
@@ -267,7 +267,7 @@ static int vhost_kernel_send_device_iotlb_msg(struct vhost_dev *dev,
             return -EFAULT;
         }
     } else {
-        struct vhost_msg msg;
+        struct vhost_msg msg = {};
 
         msg.type = VHOST_IOTLB_MSG;
         msg.iotlb = *imsg;
-- 
2.26.2