[ovs-dev] [PATCH v2 2/3] netdev-dpdk: avoid reconfiguration on VIRTIO_NET_F_MQ changes

[Kevin Traynor]

On 16/04/2019 10:45, David Marchand wrote:
> At the moment, a malicious guest might negotiate VIRTIO_NET_F_MQ and
> !VIRTIO_NET_F_MQ in a loop which would be seen as qp_num going from 1 to
> n and n to 1 continuously, triggering datapath reconfigurations at each
> transition.
> 
> Limit this by only reconfiguring on increased qp_num.
> The previous patch reduced the observed cost of polling disabled queues,
> so the only cost is memory.
> 
> Signed-off-by: David Marchand <david.marchand at redhat.com>
> ---
>  lib/netdev-dpdk.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
> index 9ba8e67..fc554db 100644
> --- a/lib/netdev-dpdk.c
> +++ b/lib/netdev-dpdk.c
> @@ -3510,8 +3510,8 @@ new_device(int vid)
>                  newnode = dev->socket_id;
>              }
>  
> -            if (dev->requested_n_txq != qp_num
> -                || dev->requested_n_rxq != qp_num
> +            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;
> 

LGTM
Acked-by: Kevin Traynor <ktraynor at redhat.com>