On 04.08.2016 12:00, Loftus, Ciara wrote:
>>
>> Binding/unbinding of virtio driver inside VM leads to reconfiguration
>> of PMD threads. This behaviour may be abused by executing bind/unbind
>> in an infinite loop to break normal networking on all ports attached
>> to the same instance of Open vSwitch.
>>
>> Fix that by avoiding reconfiguration if it's not necessary.
>> Number of queues will not be decreased to 1 on device disconnection but
>> it's not very important in comparison with possible DOS attack from the
>> inside of guest OS.
>>
>> Fixes: 81acebdaaf27 ("netdev-dpdk: Obtain number of queues for vhost
>> ports from attached virtio.")
>> Reported-by: Ciara Loftus <[email protected]>
>> Signed-off-by: Ilya Maximets <[email protected]>
>> ---
>> lib/netdev-dpdk.c | 17 ++++++++---------
>> 1 file changed, 8 insertions(+), 9 deletions(-)
>>
>> diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
>> index a0d541a..98369f1 100644
>> --- a/lib/netdev-dpdk.c
>> +++ b/lib/netdev-dpdk.c
>> @@ -2273,11 +2273,14 @@ new_device(struct virtio_net *virtio_dev)
>> newnode = dev->socket_id;
>> }
>>
>> - dev->requested_socket_id = newnode;
>> - dev->requested_n_rxq = qp_num;
>> - dev->requested_n_txq = qp_num;
>> - netdev_request_reconfigure(&dev->up);
>> -
>> + if (dev->requested_n_txq != qp_num
>> + || dev->requested_n_rxq != qp_num
>> + || dev->requested_socket_id != newnode) {
>> + dev->requested_socket_id = newnode;
>> + dev->requested_n_rxq = qp_num;
>> + dev->requested_n_txq = qp_num;
>> + netdev_request_reconfigure(&dev->up);
>> + }
>> ovsrcu_set(&dev->virtio_dev, virtio_dev);
>> exists = true;
>>
>> @@ -2333,11 +2336,7 @@ destroy_device(volatile struct virtio_net
>> *virtio_dev)
>> ovs_mutex_lock(&dev->mutex);
>> virtio_dev->flags &= ~VIRTIO_DEV_RUNNING;
>> ovsrcu_set(&dev->virtio_dev, NULL);
>> - /* Clear tx/rx queue settings. */
>> netdev_dpdk_txq_map_clear(dev);
>> - dev->requested_n_rxq = NR_QUEUE;
>> - dev->requested_n_txq = NR_QUEUE;
>> - netdev_request_reconfigure(&dev->up);
>
> Hi Ilya,
>
> I assume we will still poll on N queues despite the device being down?
> Do you have any data showing how this may affect performance?
No, I haven't. But it must be negligible because there will be instant
return from 'netdev_dpdk_vhost_rxq_recv()'. Anyway we're polling
queue #0 now all the time. Also, I think that the state when no driver
loaded for device should not last long.
Best regards, Ilya Maximets.
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