virtio_net: flush uncompleted TX on reset
If the backend could not transmit a packet right away for some reason,
the packet is queued for asynchronous sending. The corresponding vq
element is tracked in the async_tx.elem field of the VirtIONetQueue,
for later freeing when the transmission is complete.
If a reset happens before completion, virtio_net_tx_complete() will push
async_tx.elem back to the guest anyway, and we end up with the inuse flag
of the vq being equal to -1. The next call to virtqueue_pop() is then
likely to fail with "Virtqueue size exceeded".
This can be reproduced easily by starting a guest with an hubport backend
that is not connected to a functional network, eg,
-device virtio-net-pci,netdev=hub0 -netdev hubport,id=hub0,hubid=0
and no other -netdev hubport,hubid=0 on the command line.
The appropriate fix is to ensure that such an asynchronous transmission
cannot survive a device reset. So for all queues, we first try to send
the packet again, and eventually we purge it if the backend still could
not deliver it.
CC: qemu-stable@nongnu.org
Reported-by: R. Nageswara Sastry <nasastry@in.ibm.com>
Buglink: https://github.com/open-power-host-os/qemu/issues/37
Signed-off-by: Greg Kurz <groug@kaod.org>
Tested-by: R. Nageswara Sastry <nasastry@in.ibm.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
(cherry picked from commit 94b52958b7
)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
stable-2.11
parent
a053477b7c
commit
db9c0d907e
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@ -422,6 +422,7 @@ static RxFilterInfo *virtio_net_query_rxfilter(NetClientState *nc)
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static void virtio_net_reset(VirtIODevice *vdev)
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{
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VirtIONet *n = VIRTIO_NET(vdev);
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int i;
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/* Reset back to compatibility mode */
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n->promisc = 1;
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@ -445,6 +446,16 @@ static void virtio_net_reset(VirtIODevice *vdev)
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memcpy(&n->mac[0], &n->nic->conf->macaddr, sizeof(n->mac));
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qemu_format_nic_info_str(qemu_get_queue(n->nic), n->mac);
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memset(n->vlans, 0, MAX_VLAN >> 3);
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/* Flush any async TX */
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for (i = 0; i < n->max_queues; i++) {
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NetClientState *nc = qemu_get_subqueue(n->nic, i);
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if (nc->peer) {
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qemu_flush_or_purge_queued_packets(nc->peer, true);
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assert(!virtio_net_get_subqueue(nc)->async_tx.elem);
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}
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}
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}
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static void peer_test_vnet_hdr(VirtIONet *n)
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@ -156,6 +156,7 @@ ssize_t qemu_send_packet_async(NetClientState *nc, const uint8_t *buf,
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int size, NetPacketSent *sent_cb);
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void qemu_purge_queued_packets(NetClientState *nc);
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void qemu_flush_queued_packets(NetClientState *nc);
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void qemu_flush_or_purge_queued_packets(NetClientState *nc, bool purge);
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void qemu_format_nic_info_str(NetClientState *nc, uint8_t macaddr[6]);
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bool qemu_has_ufo(NetClientState *nc);
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bool qemu_has_vnet_hdr(NetClientState *nc);
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