virtio: Call set_features during reset

virtio-net expects set_features() will be called when the feature set
used by the guest changes to update the number of virtqueues but it is
not called during reset, which will clear all features, leaving the
queues added for VIRTIO_NET_F_MQ or VIRTIO_NET_F_RSS. Not only these
extra queues are visible to the guest, they will cause segmentation
fault during migration.

Call set_features() during reset to remove those queues for virtio-net
as we call set_status(). It will also prevent similar bugs for
virtio-net and other devices in the future.

Fixes: f9d6dbf ("virtio-net: remove virtio queues if the guest doesn't support multiqueue")
Buglink: https://issues.redhat.com/browse/RHEL-73842
Cc: [email protected]
Signed-off-by: Akihiko Odaki <[email protected]>
Message-Id: <[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
(cherry picked from commit 0caed25)
Signed-off-by: Michael Tokarev <[email protected]>

Author: akihikodaki

hw/virtio/virtio.c

@@ -2316,6 +2316,8 @@ void virtio_queue_enable(VirtIODevice *vdev, uint32_t queue_index)
     }
 }
 
+static int virtio_set_features_nocheck(VirtIODevice *vdev, uint64_t val);
+
 void virtio_reset(void *opaque)
 {
     VirtIODevice *vdev = opaque;
@@ -2346,7 +2348,7 @@ void virtio_reset(void *opaque)
     vdev->start_on_kick = false;
     vdev->started = false;
     vdev->broken = false;
-    vdev->guest_features = 0;
+    virtio_set_features_nocheck(vdev, 0);
     vdev->queue_sel = 0;
     vdev->status = 0;
     vdev->disabled = false;