Re: [dpdk-dev] [PATCH] app/testpmd: change port detach interface

["Yigit, Ferruh" <ferruh.yigit@linux.intel.com>]

On 5/29/2019 9:16 AM, Nithin Dabilpuram wrote:
> Hi Thomas,
> 
> On Mon, May 20, 2019 at 06:20:53PM +0530, Nithin Dabilpuram wrote:
>> On Fri, May 17, 2019 at 10:59:38AM +0200, Thomas Monjalon wrote:
>>> 17/05/2019 10:55, Nithin Dabilpuram:
>>>> On Wed, May 15, 2019 at 09:27:22AM +0200, Thomas Monjalon wrote:
>>>>> 15/05/2019 08:52, Nithin Dabilpuram:
>>>>>> Hi Thomas,
>>>>>> On Tue, May 14, 2019 at 05:39:30PM +0200, Thomas Monjalon wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> 13/05/2019 13:21, Nithin Dabilpuram:
>>>>>>>> With the latest published interface of
>>>>>>>> rte_eal_hotplug_[add,remove](), and rte_eth_dev_close(),
>>>>>>>> rte_eth_dev_close() would cleanup all the data structures of
>>>>>>>> port's eth dev leaving the device common resource intact
>>>>>>>> if RTE_ETH_DEV_CLOSE_REMOVE is set in dev flags.
>>>>>>>> So "port detach" (~hotplug remove) should be able to work,
>>>>>>>> with device identifier like "port attach" as eth_dev could have
>>>>>>>> been closed already and rte_eth_devices[port_id] reused.
>>>>>>>
>>>>>>> "port attach" uses devargs as identifier because there
>>>>>>> is no port id before creating it. But "detach port" uses
>>>>>>> logically the port id to close.
>>>>>>
>>>>>> But if "port close" was already called on that port,
>>>>>> eth_dev->state would be set as RTE_ETH_DEV_UNUSED and
>>>>>> that port id could be reused.
>>>>>> So after "port close" if we call "port detach", isn't it
>>>>>> incorrect to use the same port id ?
>>>>>
>>>>> Yes it is incorrect to close a port which is already closed :)
>>>>>
>>>>>>>> This change alters "port detach" cmdline interface to
>>>>>>>> work with device identifier like "port attach".
>>>>>>>
>>>>>>> The word "port" means an ethdev port, so it should be
>>>>>>> referenced with a port id.
>>>>>>> If you want to close an EAL rte_device, then you should
>>>>>>> rename the command.
>>>>>>> But testpmd purpose should be to work with ethdev ports only.
>>>>>>
>>>>>> Renaming the command to "detach <identifier>" ?
>>>>>
>>>>> Yes something like that.
>>>>> But why do you want to manage rte_device in testpmd?
>>>>> Being able to close ports in not enough?
>>>>> Please describe a scenario.
>>>>>
>>>>
>>>> We just want to support testing hotplug detach along with
>>>> hotplug attach from testpmd. Currently there is no way to detach
>>>> if we close the port first.
>>>
>>> OK
>> So can I send next revision with command renamed to "detach <identifier>" ?
> 
> Any info on this ? I can even add it as another cmd without disturbing existing
> command if needed.

This sounds better option to me. I see the need to remove device via
'identifier' but also still it is easier to use 'port_id' for removal when
applicable, so I am for keeping it.

What do you think adding a new command:
'device detach'

Also testpmd doesn't dead with 'device' much, it mainly works in port level,
because of this does it make sense to add another command something like:
"show device info all"

> 
>>>
>>>> Another reason is that in our new PMD, for detaching one specific port,
>>>> we need more than one try as the PMD might return -EAGAIN.
>>>> So with the current "port detach" implementation, after closing the port,
>>>> if PMD returns -EAGAIN for rte_dev_remove() call, there is no way to
>>>> try it again.
>>>
>>> This is a bug.
>>> Should we catch -EAGAIN somewhere?
>>
>> It is already caught in local_dev_remove() and
>> rte_dev_remove() fails. Only problem as I said below is
>> in testpmd if first call to detach_port_device() i.e handler of "port detach", 
>> rte_dev_remove() returns -EAGAIN and PMD cleaned up the resources partially like eth_dev
>> resources, the second time call cannot work port_id will not be valid anymore.
>>
>>>
>>>