[dpdk-dev] [PATCH v3] i40e: configure MTU

[Xing, Beilei]

> -----Original Message-----
> From: Ananyev, Konstantin
> Sent: Monday, June 20, 2016 4:05 PM
> To: Xing, Beilei <beilei.xing at intel.com>; Yong Wang
> <yongwang at vmware.com>; Olivier Matz <olivier.matz at 6wind.com>; Wu,
> Jingjing <jingjing.wu at intel.com>
> Cc: dev at dpdk.org; Julien Meunier <julien.meunier at 6wind.com>; Thomas
> Monjalon <thomas.monjalon at 6wind.com>
> Subject: RE: [dpdk-dev] [PATCH v3] i40e: configure MTU
> 
> 
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Xing, Beilei
> > Sent: Monday, June 20, 2016 5:50 AM
> > To: Yong Wang; Olivier Matz; Wu, Jingjing
> > Cc: dev at dpdk.org; Julien Meunier; Thomas Monjalon
> > Subject: Re: [dpdk-dev] [PATCH v3] i40e: configure MTU
> >
> >
> > > -----Original Message-----
> > > From: Yong Wang [mailto:yongwang at vmware.com]
> > > Sent: Friday, June 17, 2016 1:40 AM
> > > To: Olivier Matz <olivier.matz at 6wind.com>; Xing, Beilei
> > > <beilei.xing at intel.com>; Wu, Jingjing <jingjing.wu at intel.com>
> > > Cc: dev at dpdk.org; Julien Meunier <julien.meunier at 6wind.com>; Thomas
> > > Monjalon <thomas.monjalon at 6wind.com>
> > > Subject: Re: [dpdk-dev] [PATCH v3] i40e: configure MTU
> > >
> > > On 5/16/16, 5:27 AM, "dev on behalf of Olivier Matz"
> > > <dev-bounces at dpdk.org on behalf of olivier.matz at 6wind.com> wrote:
> > >
> > > >Hi Beilei,
> > > >
> > > >On 05/13/2016 10:15 AM, Beilei Xing wrote:
> > > >> This patch enables configuring MTU for i40e.
> > > >> Since changing MTU needs to reconfigure queue, stop port first
> > > >> before configuring MTU.
> > > >>
> > > >> Signed-off-by: Beilei Xing <beilei.xing at intel.com>
> > > >> ---
> > > >> v3 changes:
> > > >>  Add frame size with extra I40E_VLAN_TAG_SIZE.
> > > >>  Delete i40e_dev_rx_init(pf) cause it will be called when port starts.
> > > >>
> > > >> v2 changes:
> > > >>  If mtu is not within the allowed range, return -EINVAL instead of
> -EBUSY.
> > > >>  Delete rxq reconfigure cause rxq reconfigure will be finished in
> > > >> i40e_dev_rx_init.
> > > >>
> > > >>  drivers/net/i40e/i40e_ethdev.c | 34
> > > >> ++++++++++++++++++++++++++++++++++
> > > >>  1 file changed, 34 insertions(+)
> > > >>
> > > >> [...]
> > > >> +static int
> > > >> +i40e_dev_mtu_set(struct rte_eth_dev *dev, uint16_t mtu) {
> > > >> +	struct i40e_pf *pf =
> I40E_DEV_PRIVATE_TO_PF(dev->data->dev_private);
> > > >> +	struct rte_eth_dev_data *dev_data = pf->dev_data;
> > > >> +	uint32_t frame_size = mtu + ETHER_HDR_LEN
> > > >> +			      + ETHER_CRC_LEN + I40E_VLAN_TAG_SIZE;
> > > >> +	int ret = 0;
> > > >> +
> > > >> +	/* check if mtu is within the allowed range */
> > > >> +	if ((mtu < ETHER_MIN_MTU) || (frame_size >
> I40E_FRAME_SIZE_MAX))
> > > >> +		return -EINVAL;
> > > >> +
> > > >> +	/* mtu setting is forbidden if port is start */
> > > >> +	if (dev_data->dev_started) {
> > > >> +		PMD_DRV_LOG(ERR,
> > > >> +			    "port %d must be stopped before configuration\n",
> > > >> +			    dev_data->port_id);
> > > >> +		return -ENOTSUP;
> > > >> +	}
> > > >
> > > >I'm not convinced that ENOTSUP is the proper return value here.
> > > >It is usually returned when a function is not implemented, which is
> > > >not the case here: the function is implemented but is forbidden
> > > >because the port is running.
> > > >
> > > >I saw that Julien commented on your v1 that the return value should
> > > >be one of:
> > > > - (0) if successful.
> > > > - (-ENOTSUP) if operation is not supported.
> > > > - (-ENODEV) if *port_id* invalid.
> > > > - (-EINVAL) if *mtu* invalid.
> > > >
> > > >But I think your initial value (-EBUSY) was fine. Maybe it should
> > > >be added in the API instead, with the following description:
> > > >  (-EBUSY) if the operation is not allowed when the port is running
> > >
> > > AFAICT, the same check is not done for other drivers that implement
> > > the mac_set op. Wouldn’t it make more sense to have the driver
> > > disable the port, reconfigure and re-enable it in this case, instead
> > > of returning error code?  If the consensus in DPDK is to have the
> > > application disable the port first, we need to enforce this policy across all
> devices and clearly document this behavior.
> > >
> > Hi,
> > For ixgbe/igb, there's register for MTU during runtime, but for i40e,
> > setting MTU is finished by firmware during configuration. There'll be some risk
> when disable the port, reconfigure and re-enable the port, so return error code
> in this case currently.
> 
> Ok, but then what is the point to introduce mtu_set() for i40e at all?
> Let's just leave it unimplemented, as it is right now.
> Then users would know that for that device they have to do
> dev_stop/dev_configure().

Hi Konstantin,
The original intention is to reduce ops gap in different PMDs, but unfortunately, setting MTU in i40e couldn’t be finished as in ixgbe, so in the function, we change the configuration and note users that if want to configure MTU, stop ports first. The sequence of configuring MTU for i40e is: port stop->set MTU->port start.
We will add according instruction in document.
Beilei

> Konstantin
> 
> > Thanks for your comments, we'll improve the document later.
> >
> > > >This would allow the application to take its dispositions to stop
> > > >the port and restart it with the proper jumbo_frame argument.
> > > >
> > > >+CC Thomas which maintains ethdev API.
> > > >
> > > >
> > > >Regards,
> > > >Olivier