[RFC PATCH 14/18] vdpa: do not set virtio status bits if unneeded

["Eugenio Pérez" <eperezma@redhat.com>]

Next commits will set DRIVER and ACKNOWLEDGE flags repeatedly in the
case of a migration destination.  Let's save ioctls with this.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-vdpa.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 7500c2fc82..cc252fc2d8 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -510,6 +510,10 @@ static int vhost_vdpa_add_status(struct vhost_dev *dev, uint8_t status)
     if (ret < 0) {
         return ret;
     }
+    if ((s & status) == status) {
+        /* Don't set bits already set */
+        return 0;
+    }
 
     s |= status;
 
-- 
2.39.3