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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> |
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| .. | ||
| can_emu.h | ||
| can_host.h | ||
| checksum.h | ||
| eth.h | ||
| filter.h | ||
| net.h | ||
| queue.h | ||
| slirp.h | ||
| tap.h | ||
| vhost-user.h | ||
| vhost_net.h | ||