[dpdk-dev] [PATCH 1/6] net/tap: use correct tap name

[Wiles, Keith]

> On Jan 31, 2017, at 9:44 AM, Pascal Mazon <pascal.mazon at 6wind.com> wrote:
> 
> On 01/31/2017 04:44 PM, Wiles, Keith wrote:
>> 
>>> On Jan 31, 2017, at 9:38 AM, Yigit, Ferruh <ferruh.yigit at intel.com> wrote:
>>> 
>>> On 1/31/2017 3:30 PM, Pascal Mazon wrote:
>>>> On 01/31/2017 04:28 PM, Ferruh Yigit wrote:
>>>>> On 1/31/2017 2:23 PM, Pascal Mazon wrote:
>>>>>> On 01/31/2017 02:06 PM, Ferruh Yigit wrote:> On 1/31/2017 9:42 AM,
>>>>>> Pascal Mazon wrote:
>>>>>>>> dev->data->name contains "net_tap", the device driver name.
>>>>>>> 
>>>>>>> I see what patch does, just as a note to commit log:
>>>>>>> 
>>>>>>> AFAIK, "dev->data->name" is device name, and for this case it is
>>>>>>> "net_tap#", like "net_tap0", "net_tap1" ...
>>>>>>> 
>>>>>>> "dev->data_drv_name" is the driver name which is "net_tap"
>>>>>> 
>>>>>> Indeed, dev->data->name is the device name, looking like "net_tap#",
>>>>>> with number increasing for each vdev.
>>>>>> I'll put the following commit log line if that's ok:
>>>>>> 
>>>>>>    dev->data->name contains the device name, e.g. "net_tap0".
>>>>>> 
>>>>>>> 
>>>>>>>> dev->data->dev_private->name contains the actual iface name,
>>>>>>>> e.g. "dtap0".
>>>>>>> 
>>>>>>> Right, I agree this is correct comparing "dev->data->name"
>>>>>>> 
>>>>>>> But the problem is pmd->name is per eth_dev.
>>>>>>> 
>>>>>>> If I read code correct, for multiple queue support, each queue pair will
>>>>>>> create a tap device, so each needs a different name.
>>>>>>> 
>>>>>>> So can't just use pmd->name. Need to create a name per queue pair, it
>>>>>>> can be combination of pmd->name + "_" + queue_id? Or can keep a name per
>>>>>>> queue pair, instead of eth_dev.
>>>>>>> 
>>>>>>> What do you think?
>>>>>> 
>>>>>> Actually that's not exactly how it goes.
>>>>>> Adding a queue to a netdevice requires to open("/dev/net/tun") and setting
>>>>>> TUNSETIFF (through ioctl) on the resulting fd.
>>>>>> That's the important part: queues for a given tap device must set TUNSETIFF
>>>>>> with a common ifreq.ifr_name (in our case, pmd->name).

Looking at the changes to set the link up/down and the adding the two functions. I noticed in the stop/start routines I was set the link in DPDK and not adjusting the interface link. Should the stop/start routine also do the same thing?

>>>>>> 
>>>>>> This is best explained in the kernel doc, there:
>>>>> 
>>>>> Thank you for the clarification.
>>>>> If so, why PMD keeps a fd per queue?
>>>>> 
>>>>> Overall, patch looks good except mentioned detail in commit log.
>>>>> 
>>>>> I suggest waiting Keith's patch, and rebase this set on top of it.
>>>>> 
>>>>> Thanks,
>>>>> ferruh
>>>>> 
>>>>>> 
>>>>>> [1]
>>>>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/networking/tuntap.txt#n108
>>>>>> 
>>>>> <...>
>>>>> 
>>>> 
>>>> I would say it is because dev->{r/t}x_pkt_burst() is done per queue.
>>>> In these functions, we need to make our read() and write() accesses on the
>>>> right fd considering the queue we're required to process.
>>> 
>>> If fd is same for all queues, it is possible to keep one instance in pmd
>>> private_data, and access it from queues. I think it is confusing to have
>>> multiple copy of it, but I see your point.
>> 
>> In my changes I removed the fds[] array as it was not required only the rx/tx_queue has an fd variable.
> 
> Sounds good to me.
> 
> Ferruh, just to make sure we're on the same page, in multiqueue, there is definitely a different fd for each queue.
> 
>> 
>>> 
>>>> 
>>>> I'll wait for Keith's patch, then.
>>> 
>>> Thanks again.
>>> 
>>>> 
>>>> Best regards,
>> 
>> Regards,
>> Keith
>> 
> 
> 
> -- 
> Pascal Mazon
> www.6wind.com

Regards,
Keith