On Tue, Sep 29, 2020 at 4:00 AM <xiangxia.m.yue@xxxxxxxxx> wrote:
>
> From: Tonghao Zhang <xiangxia.m.yue@xxxxxxxxx>
>
> Open vSwitch and Linux bridge will disable LRO of the interface
> when this interface added to them. Now when disable the LRO, the
> virtio-net csum is disable too. That drops the forwarding performance.
I had focused on the code previously.
The s/w checksum verification cost is significant in a VM with traffic
to local destinations. A bridge does not verify transport layer
checksums OTOH?
> Fixes: a02e8964eaf9 ("virtio-net: ethtool configurable LRO")
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Cc: Jason Wang <jasowang@xxxxxxxxxx>
> Cc: Willem de Bruijn <willemb@xxxxxxxxxx>
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@xxxxxxxxx>
> ---
> v2:
> * change the fix-tag
> ---
> drivers/net/virtio_net.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 7145c83c6c8c..21b71148c532 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -63,6 +63,11 @@ static const unsigned long guest_offloads[] = {
> VIRTIO_NET_F_GUEST_CSUM
> };
>
> +#define GUEST_OFFLOAD_LRO_MASK ((1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
> + (1ULL << VIRTIO_NET_F_GUEST_TSO6) | \
> + (1ULL << VIRTIO_NET_F_GUEST_ECN) | \
> + (1ULL << VIRTIO_NET_F_GUEST_UFO))
> +
> struct virtnet_stat_desc {
> char desc[ETH_GSTRING_LEN];
> size_t offset;
> @@ -2531,7 +2536,8 @@ static int virtnet_set_features(struct net_device *dev,
> if (features & NETIF_F_LRO)
> offloads = vi->guest_offloads_capable;
> else
> - offloads = 0;
> + offloads = vi->guest_offloads_capable &
> + ~GUEST_OFFLOAD_LRO_MASK;
>
> err = virtnet_set_guest_offloads(vi, offloads);
> if (err)
> --
> 2.23.0
>
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