On 17-01-04 07:11 PM, John Fastabend wrote:
> XDP programs can not consume multiple pages so we cap the MTU to
> avoid this case. Virtio-net however only checks the MTU at XDP
> program load and does not block MTU changes after the program
> has loaded.
>
> This patch sets/clears the max_mtu value at XDP load/unload time.
>
> Signed-off-by: John Fastabend <john.r.fastab...@intel.com>
> ---
> drivers/net/virtio_net.c | 26 ++++++++++++++++++++++----
> 1 file changed, 22 insertions(+), 4 deletions(-)
[...]
> static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog)
> {
> - unsigned long int max_sz = PAGE_SIZE - sizeof(struct padded_vnet_hdr);
> struct virtnet_info *vi = netdev_priv(dev);
> struct bpf_prog *old_prog;
> + unsigned long int max_sz;
> u16 xdp_qp = 0, curr_qp;
> int i, err;
>
> @@ -1720,6 +1737,7 @@ static int virtnet_xdp_set(struct net_device *dev,
> struct bpf_prog *prog)
> return -EINVAL;
> }
>
> + max_sz = virtnet_xdp_mtu(prog, vi);
> if (dev->mtu > max_sz) {
> netdev_warn(dev, "XDP requires MTU less than %lu\n", max_sz);
> return -EINVAL;
> @@ -1748,6 +1766,9 @@ static int virtnet_xdp_set(struct net_device *dev,
> struct bpf_prog *prog)
> virtnet_set_queues(vi, curr_qp);
> return PTR_ERR(prog);
> }
> + dev->max_mtu = max_sz;
> + } else {
> + dev->max_mtu = ETH_MAX_MTU;
> }
oops v2 needed. The else branch is not required anymore. :/
