netdev - Re: [PATCH net] vmxnet3: use gro callback when UPT is enabled

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Date:   Thu, 9 Mar 2023 08:34:05 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Ronak Doshi <doshir@...are.com>, <netdev@...r.kernel.org>
CC:     <stable@...r.kernel.org>,
        VMware PV-Drivers Reviewers <pv-drivers@...are.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Guolin Yang <gyang@...are.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] vmxnet3: use gro callback when UPT is enabled

On 2023/3/9 6:25, Ronak Doshi wrote:
> Currently, vmxnet3 uses GRO callback only if LRO is disabled. However,
> on smartNic based setups where UPT is supported, LRO can be enabled
> from guest VM but UPT devicve does not support LRO as of now. In such
> cases, there can be performance degradation as GRO is not being done.
> 
> This patch fixes this issue by calling GRO API when UPT is enabled. We
> use updateRxProd to determine if UPT mode is active or not.
> 
> Cc: stable@...r.kernel.org
> Fixes: 6f91f4ba046e ("vmxnet3: add support for capability registers")
> Signed-off-by: Ronak Doshi <doshir@...are.com>
> Acked-by: Guolin Yang <gyang@...are.com>
> ---
>  drivers/net/vmxnet3/vmxnet3_drv.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/vmxnet3/vmxnet3_drv.c b/drivers/net/vmxnet3/vmxnet3_drv.c
> index 682987040ea8..8f7ac7d85afc 100644
> --- a/drivers/net/vmxnet3/vmxnet3_drv.c
> +++ b/drivers/net/vmxnet3/vmxnet3_drv.c
> @@ -1688,7 +1688,8 @@ vmxnet3_rq_rx_complete(struct vmxnet3_rx_queue *rq,
>  			if (unlikely(rcd->ts))
>  				__vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), rcd->tci);
>  
> -			if (adapter->netdev->features & NETIF_F_LRO)
> +			/* Use GRO callback if UPT is enabled */
> +			if ((adapter->netdev->features & NETIF_F_LRO) && !rq->shared->updateRxProd)

If UPT devicve does not support LRO, why not just clear the NETIF_F_LRO from
adapter->netdev->features?

With above change, it seems that LRO is supported for user' POV, but the GRO
is actually being done.

Also, if NETIF_F_LRO is set, do we need to clear the NETIF_F_GRO bit, so that
there is no confusion for user?

>  				netif_receive_skb(skb);
>  			else
>  				napi_gro_receive(&rq->napi, skb);
>