Re: [dpdk-dev] [v3] net/virtio: set offload flag for jumbo frames

[Jens Freimann <jfreimann@redhat.com>]

On Thu, Jan 31, 2019 at 02:01:53PM +0300, Ilya Maximets wrote:
>On 31.01.2019 12:17, Jens Freimann wrote:
>> Port configuration fails because offload flags don't match the expected
>> value when max-pkt-len is set to a value that should enable receive port
>> offloading but doesn't.
>>
>> There are two cases to consider:
>>
>> 1. VIRTIO_NET_F_MTU is set. Then we need to check if the requested
>>    max-pkt-len fits into the MTU plus header. If yes we set the
>>    offload flag.
>> 2. VIRTIO_NET_F_MTU is not set. We can set the offload flag.
>>
>> Fixes: a4996bd89c42 ("ethdev: new Rx/Tx offloads API")
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Jens Freimann <jfreimann@redhat.com>
>> Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>> ---
>> v2->v3:
>>  * remove unnecessary brackets (Maxime)
>>  * fix commit message (David)
>>
>> v1->v2:
>>  * include virtnet hdr, ethernet header, vlan tag when comparing against
>>    max-rx-pkt-len (Maxime)
>>
>>  drivers/net/virtio/virtio_ethdev.c | 14 ++++++++++++++
>>  1 file changed, 14 insertions(+)
>>
>> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
>> index 7c4c1df00..f39d4e630 100644
>> --- a/drivers/net/virtio/virtio_ethdev.c
>> +++ b/drivers/net/virtio/virtio_ethdev.c
>> @@ -2351,6 +2351,20 @@ virtio_dev_info_get(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
>>  	if ((host_features & tso_mask) == tso_mask)
>>  		dev_info->rx_offload_capa |= DEV_RX_OFFLOAD_TCP_LRO;
>>
>> +	if (host_features & (1ULL << VIRTIO_NET_F_MTU)) {
>> +		struct virtio_net_config config;
>> +		uint32_t ether_hdr_len = ETHER_HDR_LEN + VLAN_TAG_LEN +
>> +			hw->vtnet_hdr_size;
>> +		vtpci_read_dev_config(hw,
>> +				offsetof(struct virtio_net_config, mtu),
>> +				&config.mtu, sizeof(config.mtu));
>> +		if (dev->data->dev_conf.rxmode.max_rx_pkt_len <=
>> +				config.mtu + ether_hdr_len)
>> +			dev_info->rx_offload_capa |= DEV_RX_OFFLOAD_JUMBO_FRAME;
>> +	} else {
>> +		dev_info->rx_offload_capa |= DEV_RX_OFFLOAD_JUMBO_FRAME;
>> +	}
>> +
>
>Why we can't just use 'hw->max_mtu' here for checking instead of
>reading 'config.mtu' ?
>Also, It's already calculated with regards to VIRTIO_NET_F_MTU.

Can't mtu have changed after device init? If not then yes, I guess we
could use hw->max_mtu.

regards,
Jens