netdev - Re: [PATCH net v2] virtio-net: don't disable guest csum when disable LRO

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Date:   Tue, 29 Sep 2020 02:23:39 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     xiangxia.m.yue@...il.com
Cc:     jasowang@...hat.com, willemb@...gle.com,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [PATCH net v2] virtio-net: don't disable guest csum when disable
 LRO

On Tue, Sep 29, 2020 at 09:58:06AM +0800, xiangxia.m.yue@...il.com wrote:
> From: Tonghao Zhang <xiangxia.m.yue@...il.com>
> 
> 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.
> 
> Fixes: a02e8964eaf9 ("virtio-net: ethtool configurable LRO")
> Cc: Michael S. Tsirkin <mst@...hat.com>
> Cc: Jason Wang <jasowang@...hat.com>
> Cc: Willem de Bruijn <willemb@...gle.com>
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@...il.com>
> ---
> 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))
> +

I think I'd rather we open-coded this, the macro is only
used in one place ...

>  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