Re: [PATCH 2/4] net/vhost: improve Tx path selection

[Tiwei Bie <tiwei.bie@intel.com>]

On Fri, Jun 01, 2018 at 02:47:56PM +0200, Maxime Coquelin wrote:
> This patch improves the Tx path selection depending on
> whether the application request for offloads, and on whether
> offload features have been negotiated.
> 
> When the application doesn't request for Tx offload features,
> the corresponding features bits aren't negotiated.
> 
> When Tx offload virtio features have been negotiated, ensure
> the simple Tx path isn't selected.
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  drivers/net/virtio/virtio_ethdev.c | 20 ++++++++++++++++++--
>  drivers/net/virtio/virtio_ethdev.h |  3 ---
>  2 files changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
> index e68e9d067..5730620ed 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -1798,8 +1798,10 @@ static int
>  virtio_dev_configure(struct rte_eth_dev *dev)
>  {
>  	const struct rte_eth_rxmode *rxmode = &dev->data->dev_conf.rxmode;
> +	const struct rte_eth_txmode *txmode = &dev->data->dev_conf.txmode;
>  	struct virtio_hw *hw = dev->data->dev_private;
>  	uint64_t rx_offloads = rxmode->offloads;
> +	uint64_t tx_offloads = txmode->offloads;
>  	uint64_t req_features;
>  	int ret;
>  
> @@ -1821,6 +1823,15 @@ virtio_dev_configure(struct rte_eth_dev *dev)
>  			(1ULL << VIRTIO_NET_F_GUEST_TSO4) |
>  			(1ULL << VIRTIO_NET_F_GUEST_TSO6);
>  
> +	if (tx_offloads & (DEV_TX_OFFLOAD_TCP_CKSUM |
> +				DEV_TX_OFFLOAD_UDP_CKSUM))

I think it's better to keep DEV_TX_OFFLOAD_TCP/UDP_CKSUM
aligned, something like:

	if (tx_offloads & (DEV_TX_OFFLOAD_TCP_CKSUM |
			   DEV_TX_OFFLOAD_UDP_CKSUM))

> +		req_features |= (1ULL << VIRTIO_NET_F_CSUM);
> +
> +	if (tx_offloads & DEV_TX_OFFLOAD_TCP_TSO)
> +		req_features |=
> +			(1ULL << VIRTIO_NET_F_HOST_TSO4) |
> +			(1ULL << VIRTIO_NET_F_HOST_TSO6);
> +
>  	/* if request features changed, reinit the device */
>  	if (req_features != hw->req_guest_features) {
>  		ret = virtio_init_device(dev, req_features);
> @@ -1885,6 +1896,11 @@ virtio_dev_configure(struct rte_eth_dev *dev)
>  			   DEV_RX_OFFLOAD_TCP_CKSUM))
>  		hw->use_simple_rx = 0;
>  
> +	if (tx_offloads & (DEV_TX_OFFLOAD_TCP_CKSUM |
> +				DEV_TX_OFFLOAD_UDP_CKSUM |
> +				DEV_TX_OFFLOAD_TCP_TSO))

Ditto. I think it's better to keep them aligned,
something like:

	if (tx_offloads & (DEV_TX_OFFLOAD_TCP_CKSUM |
			   DEV_TX_OFFLOAD_UDP_CKSUM |
			   DEV_TX_OFFLOAD_TCP_TSO))

Besides, we also need to consider not using simple Tx
when DEV_TX_OFFLOAD_VLAN_INSERT is requested.

Best regards,
Tiwei Bie

> +		hw->use_simple_tx = 0;
> +
>  	return 0;
>  }
>  
> @@ -2138,14 +2154,14 @@ virtio_dev_info_get(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
>  
>  	dev_info->tx_offload_capa = DEV_TX_OFFLOAD_MULTI_SEGS |
>  				    DEV_TX_OFFLOAD_VLAN_INSERT;
> -	if (hw->guest_features & (1ULL << VIRTIO_NET_F_CSUM)) {
> +	if (host_features & (1ULL << VIRTIO_NET_F_CSUM)) {
>  		dev_info->tx_offload_capa |=
>  			DEV_TX_OFFLOAD_UDP_CKSUM |
>  			DEV_TX_OFFLOAD_TCP_CKSUM;
>  	}
>  	tso_mask = (1ULL << VIRTIO_NET_F_HOST_TSO4) |
>  		(1ULL << VIRTIO_NET_F_HOST_TSO6);
> -	if ((hw->guest_features & tso_mask) == tso_mask)
> +	if ((host_features & tso_mask) == tso_mask)
>  		dev_info->tx_offload_capa |= DEV_TX_OFFLOAD_TCP_TSO;
>  }
>  
> diff --git a/drivers/net/virtio/virtio_ethdev.h b/drivers/net/virtio/virtio_ethdev.h
> index bb40064ea..b603665c7 100644
> --- a/drivers/net/virtio/virtio_ethdev.h
> +++ b/drivers/net/virtio/virtio_ethdev.h
> @@ -28,9 +28,6 @@
>  	 1u << VIRTIO_NET_F_CTRL_VQ	  |	\
>  	 1u << VIRTIO_NET_F_CTRL_RX	  |	\
>  	 1u << VIRTIO_NET_F_CTRL_VLAN	  |	\
> -	 1u << VIRTIO_NET_F_CSUM	  |	\
> -	 1u << VIRTIO_NET_F_HOST_TSO4	  |	\
> -	 1u << VIRTIO_NET_F_HOST_TSO6	  |	\
>  	 1u << VIRTIO_NET_F_MRG_RXBUF	  |	\
>  	 1u << VIRTIO_NET_F_MTU	| \
>  	 1ULL << VIRTIO_NET_F_GUEST_ANNOUNCE |	\
> -- 
> 2.14.3
>