[Qemu-devel] [PATCH] clean up callback when del virtqueue

[liujunjie]

Before, we did not clear callback like handle_output when delete
the virtqueue which may result be segmentfault.
The scene is as follows:
1. Start a vm with multiqueue vhost-net,
2. then we write VIRTIO_PCI_GUEST_FEATURES in PCI configuration to
triger multiqueue disable in this vm which will delete the virtqueue.
In this step, the tx_bh is deleted but the callback virtio_net_handle_tx_bh
still exist.
3. Finally, we write VIRTIO_PCI_QUEUE_NOTIFY in PCI configuration to
notify the deleted virtqueue. In this way, virtio_net_handle_tx_bh
will be called and qemu will be crashed.
Although the way described above is uncommon, we had better reinforce it.

Signed-off-by: liujunjie <liujunji...@huawei.com>
---
 hw/net/virtio-net.c | 4 +++-
 hw/virtio/virtio.c  | 3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index f154756..9bb20e3 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1467,7 +1467,9 @@ static void virtio_net_handle_tx_bh(VirtIODevice *vdev, 
VirtQueue *vq)
         return;
     }
     virtio_queue_set_notification(vq, 0);
-    qemu_bh_schedule(q->tx_bh);
+    if (q->tx_bh) {
+        qemu_bh_schedule(q->tx_bh);
+    }
 }
 
 static void virtio_net_tx_timer(void *opaque)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index d4e4d98..7577518 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1604,6 +1604,9 @@ void virtio_del_queue(VirtIODevice *vdev, int n)
 
     vdev->vq[n].vring.num = 0;
     vdev->vq[n].vring.num_default = 0;
+    vdev->vq[n].vring.align = 0;
+    vdev->vq[n].handle_output = NULL;
+    vdev->vq[n].handle_aio_output = NULL;
 }
 
 static void virtio_set_isr(VirtIODevice *vdev, int value)
-- 
1.8.3.1