Re: [PATCH v1] examples/l3fwd: relax the RSS/Offload requirement

[Konstantin Ananyev <konstantin.v.ananyev@yandex.ru>]

03/09/2023 05:01, Trevor Tao пишет:
> Now the port Rx mq_mode had been set to RTE_ETH_MQ_RX_RSS, and offload
> mode set to RTE_ETH_RX_OFFLOAD_CHECKSUM by default, but some hardware
> and/or virtual interface does not support the RSS and offload mode
> presupposed, e.g., some virtio interfaces in the cloud don't support
> RSS and may only partly support RTE_ETH_RX_OFFLOAD_UDP_CKSUM/
> RTE_ETH_RX_OFFLOAD_TCP_CKSUM,
> but not RTE_ETH_RX_OFFLOAD_IPV4_CKSUM, and the error msg here:
> 
> virtio_dev_configure(): RSS support requested but not supported by
> the device
> Port0 dev_configure = -95
> 
> and:
> Ethdev port_id=0 requested Rx offloads 0xe does not match Rx offloads
> capabilities 0x201d in rte_eth_dev_configure()
> 
> So to enable the l3fwd running in that environment, the Rx mode requirement
> can be relaxed to reflect the hardware feature reality here, and the l3fwd
> can run smoothly then.
> A warning msg would be provided to user in case it happens here.
> 
> On the other side, enabling the software cksum check in case the
> hw support missing.
> 
> Fixes: af75078fece3 ("first public release")
> Cc: stable@dpdk.org

I don't think there was abug here.
We are talking about changing current requirements for the app.
So not sure it is a real fix and that such change can be
propagated to stable releases.

> 
> Signed-off-by: Trevor Tao <taozj888@163.com>
> ---
>   examples/l3fwd/l3fwd.h | 12 +++++++++++-
>   examples/l3fwd/main.c  | 21 +++++++++++++++++++--
>   2 files changed, 30 insertions(+), 3 deletions(-)
> 
> diff --git a/examples/l3fwd/l3fwd.h b/examples/l3fwd/l3fwd.h
> index b55855c932..cc10643c4b 100644
> --- a/examples/l3fwd/l3fwd.h
> +++ b/examples/l3fwd/l3fwd.h
> @@ -115,6 +115,8 @@ extern struct acl_algorithms acl_alg[];
>   
>   extern uint32_t max_pkt_len;
>   
> +extern struct rte_eth_conf port_conf;
> +
>   /* Send burst of packets on an output interface */
>   static inline int
>   send_burst(struct lcore_conf *qconf, uint16_t n, uint16_t port)
> @@ -170,7 +172,15 @@ is_valid_ipv4_pkt(struct rte_ipv4_hdr *pkt, uint32_t link_len)
>   		return -1;
>   
>   	/* 2. The IP checksum must be correct. */
> -	/* this is checked in H/W */
> +	/* if this is not checked in H/W, check it. */
> +	if ((port_conf.rxmode.offloads & RTE_ETH_RX_OFFLOAD_IPV4_CKSUM) == 0) {

Might be better to check particular mbuf flag:
if ((mbuf->ol_flags & RTE_MBUF_F_RX_IP_CKSUM_MASK) == 
TE_MBUF_F_RX_IP_CKSUM_UNKNOWN) {...}

> +		uint16_t actual_cksum, expected_cksum;
> +		actual_cksum = pkt->hdr_checksum;
> +		pkt->hdr_checksum = 0;
> +		expected_cksum = rte_ipv4_cksum(pkt);
> +		if (actual_cksum != expected_cksum)
> +			return -2;
> +	}
>   
>   	/*
>   	 * 3. The IP version number must be 4. If the version number is not 4
> diff --git a/examples/l3fwd/main.c b/examples/l3fwd/main.c
> index 6063eb1399..37aec64718 100644
> --- a/examples/l3fwd/main.c
> +++ b/examples/l3fwd/main.c
> @@ -117,7 +117,7 @@ static struct lcore_params * lcore_params = lcore_params_array_default;
>   static uint16_t nb_lcore_params = sizeof(lcore_params_array_default) /
>   				sizeof(lcore_params_array_default[0]);
>   
> -static struct rte_eth_conf port_conf = {
> +struct rte_eth_conf port_conf = {
>   	.rxmode = {
>   		.mq_mode = RTE_ETH_MQ_RX_RSS,
>   		.offloads = RTE_ETH_RX_OFFLOAD_CHECKSUM,
> @@ -1257,8 +1257,12 @@ l3fwd_poll_resource_setup(void)
>   		local_port_conf.rx_adv_conf.rss_conf.rss_hf &=
>   			dev_info.flow_type_rss_offloads;
>   
> -		if (dev_info.max_rx_queues == 1)
> +		/* relax the rx rss requirement */
> +		if (dev_info.max_rx_queues == 1 || !local_port_conf.rx_adv_conf.rss_conf.rss_hf) {
> +			printf("warning: modified the rx mq_mode to RTE_ETH_MQ_RX_NONE base on"
> +				" device capability\n");
>   			local_port_conf.rxmode.mq_mode = RTE_ETH_MQ_RX_NONE;

Should we probably instead have a new commnad-line option to explicitly 
disable RSS?
Something like: '--no-rss' or so?

> +		}
>   
>   		if (local_port_conf.rx_adv_conf.rss_conf.rss_hf !=
>   				port_conf.rx_adv_conf.rss_conf.rss_hf) {
> @@ -1269,6 +1273,19 @@ l3fwd_poll_resource_setup(void)
>   				local_port_conf.rx_adv_conf.rss_conf.rss_hf);
>   		}
>   
> +		/* relax the rx offload requirement */
> +		if ((local_port_conf.rxmode.offloads & dev_info.rx_offload_capa) !=
> +			local_port_conf.rxmode.offloads) {
> +			printf("Port %u requested Rx offloads 0x%"PRIx64" does not"
> +				" match Rx offloads capabilities 0x%"PRIx64"\n",
> +				portid, local_port_conf.rxmode.offloads,
> +				dev_info.rx_offload_capa);
> +			local_port_conf.rxmode.offloads &= dev_info.rx_offload_capa;
> +			port_conf.rxmode.offloads = local_port_conf.rxmode.offloads;

Why to remove offloads in port_conf?
There could be multiple ports, and on others desired HW offloads might 
be supported.

> +			printf("warning: modified the rx offload to 0x%"PRIx64" based on device"
> +				" capability\n", local_port_conf.rxmode.offloads);
> +		}
> +
>   		ret = rte_eth_dev_configure(portid, nb_rx_queue,
>   					(uint16_t)n_tx_queue, &local_port_conf);
>   		if (ret < 0)