[dpdk-dev] [PATCH v2 36/46] net/liquidio: add API to set MTU

[Ferruh Yigit]

On 3/21/2017 12:53 PM, Shijith Thotton wrote:
> On Tue, Mar 21, 2017 at 12:24:49PM +0000, Ferruh Yigit wrote:
>> On 3/2/2017 11:32 AM, Shijith Thotton wrote:
>>> Signed-off-by: Shijith Thotton <shijith.thotton at caviumnetworks.com>
>>> Signed-off-by: Jerin Jacob <jerin.jacob at caviumnetworks.com>
>>> Signed-off-by: Derek Chickles <derek.chickles at caviumnetworks.com>
>>> Signed-off-by: Venkat Koppula <venkat.koppula at caviumnetworks.com>
>>> Signed-off-by: Srisivasubramanian S <ssrinivasan at caviumnetworks.com>
>>> Signed-off-by: Mallesham Jatharakonda <mjatharakonda at oneconvergence.com>
>>
>> <...>
>>
>>>  
>>>  static int
>>> +lio_dev_change_vf_mtu(struct rte_eth_dev *eth_dev, uint16_t new_mtu)
>>> +{
>>> +	struct lio_device *lio_dev = LIO_DEV(eth_dev);
>>> +
>>> +	PMD_INIT_FUNC_TRACE();
>>> +
>>> +	if (!lio_dev->intf_open) {
>>> +		lio_dev_err(lio_dev, "Port %d down, can't change MTU\n",
>>> +			    lio_dev->port_id);
>>> +		return -EINVAL;
>>> +	}
>>> +
>>> +	/* Limit the MTU to make sure the ethernet packets are between
>>> +	 * ETHER_MIN_MTU bytes and PF's MTU
>>> +	 */
>>> +	if ((new_mtu < ETHER_MIN_MTU) ||
>>> +			(new_mtu > lio_dev->linfo.link.s.mtu)) {
>>> +		lio_dev_err(lio_dev, "Invalid MTU: %d\n", new_mtu);
>>> +		lio_dev_err(lio_dev, "Valid range %d and %d\n",
>>> +			    ETHER_MIN_MTU, lio_dev->linfo.link.s.mtu);
>>> +		return -EINVAL;
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>
>> Is this really sets the MTU?
>> "new_mtu" seems not used, except limit check, an lio_send_ctrl_pkt()
>> required perhaps?
> 
> It won't set MTU for hardware and is possible only by PF. So
> lio_send_ctrl_pkt is not required. VF MTU is limited by PF MTU and is
> mentioned under limitations in driver documentation. Here we are
> allowing upper layer to set MTU up to the value configured by PF.

I see, but lio_dev_change_vf_mtu() does not set anything at all. If it
is not modifying anything at all, why you claim "MTU update" supported?

And following logic seems wrong for this case:

	...
	if (lio_dev->linfo.link.s.mtu != mtu) {
		ret = lio_dev_change_vf_mtu(eth_dev, mtu);
	...

Should this functions set lio_dev->linfo.link.s.mtu at least, perhaps?

> 
> Shijith
>