virtio-net: don't touch virtqueue if vm is stopped

Guest state should not be touched if VM is stopped, unfortunately we
didn't check running state and tried to drain tx queue unconditionally
in virtio_net_set_status(). A crash was then noticed as a migration
destination when user type quit after virtqueue state is loaded but
before region cache is initialized. In this case,
virtio_net_drop_tx_queue_data() tries to access the uninitialized
region cache.

Fix this by only dropping tx queue data when vm is running.

Fixes: 283e2c2adcb80 ("net: virtio-net discards TX data after link down")
Cc: Yuri Benditovich <yuri.benditovich@daynix.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: qemu-stable@nongnu.org
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
(cherry picked from commit 70e53e6e4da3db4b2c31981191753a7e974936d0)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 148071a3969986aec119c040d6924ea8e7a145d7..fbc5e1bd73e4a43772582adcea91336990507022 100644 (file)
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -288,7 +288,8 @@ static void virtio_net_set_status(struct VirtIODevice *vdev, uint8_t status)
                 qemu_bh_cancel(q->tx_bh);
             }
             if ((n->status & VIRTIO_NET_S_LINK_UP) == 0 &&
-                (queue_status & VIRTIO_CONFIG_S_DRIVER_OK)) {
+                (queue_status & VIRTIO_CONFIG_S_DRIVER_OK) &&
+                vdev->vm_running) {
                 /* if tx is waiting we are likely have some packets in tx queue
                  * and disabled notification */
                 q->tx_waiting = 0;