Re: [RFC PATCH 2/9] virtio_net: set up xdp for multi buffer packets

Heng Qi
2022-12-08T08:21:21Z

在 2022/12/6 下午1:29, Jason Wang 写道:
> On Tue, Nov 22, 2022 at 3:44 PM Heng Qi <hengqi@linux.alibaba.com> wrote:
>> When the xdp program sets xdp.frags, which means it can process
>> multi-buffer packets, so we continue to open xdp support when
>> features such as GRO_HW are negotiated.
>>
>> Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
>> Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
>> ---
>> drivers/net/virtio_net.c | 30 +++++++++++++++++-------------
>> 1 file changed, 17 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index c5046d21b281..8f7d207d58d6 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -3080,14 +3080,21 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
>> u16 xdp_qp = 0, curr_qp;
>> int i, err;
>>
>> - if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)
>> - && (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
>> - virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
>> - virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
>> - virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO) ||
>> - virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))) {
>> - NL_SET_ERR_MSG_MOD(extack, "Can't set XDP while host is implementing GRO_HW/CSUM, disable GRO_HW/CSUM first");
>> - return -EOPNOTSUPP;
>> + if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)) {
>> + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM)) {
>> + NL_SET_ERR_MSG_MOD(extack, "Can't set XDP without frags while guest is implementing GUEST_CSUM");
>> + return -EOPNOTSUPP;
>> + }
>> +
>> + if (prog && !prog->aux->xdp_has_frags) {
>> + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
>> + virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
>> + virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
>> + virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO)) {
>> + NL_SET_ERR_MSG_MOD(extack, "Can't set XDP without frags while guest is implementing GUEST_GRO_HW");
>> + return -EOPNOTSUPP;
>> + }
>> + }
>> }
>>
>> if (vi->mergeable_rx_bufs && !vi->any_header_sg) {
>> @@ -3095,8 +3102,8 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
>> return -EINVAL;
>> }
>>
>> - if (dev->mtu > max_sz) {
>> - NL_SET_ERR_MSG_MOD(extack, "MTU too large to enable XDP");
>> + if (prog && !prog->aux->xdp_has_frags && dev->mtu > max_sz) {
>> + NL_SET_ERR_MSG_MOD(extack, "MTU too large to enable XDP without frags");
>> netdev_warn(dev, "XDP requires MTU less than %lu\n", max_sz);
>> return -EINVAL;
>> }
>> @@ -3218,9 +3225,6 @@ static int virtnet_set_features(struct net_device *dev,
>> int err;
>>
>> if ((dev->features ^ features) & NETIF_F_GRO_HW) {
>> - if (vi->xdp_enabled)
>> - return -EBUSY;
> This seems suspicious, GRO_HW could be re-enabled accidentally even if
> it was disabled when attaching an XDP program that is not capable of
> doing multi-buffer XDP?

Yes, we shouldn't drop this check, because GRO_HW is unfriendly to xdp
programs without xdp.frags.

Thanks.

>
> Thanks
>
>> -
>> if (features & NETIF_F_GRO_HW)
>> offloads = vi->guest_offloads_capable;
>> else
>> --
>> 2.19.1.6.gb485710b
>>