[dpdk-dev] [EXT] Re: [PATCH 2/2] net/qede: restore Tx queue setup

[Ferruh Yigit]

On 5/6/2020 3:43 AM, Rasesh Mody wrote:
> Hi,
> 
>> From: Thomas Monjalon <thomas at monjalon.net>
>> Sent: Tuesday, May 05, 2020 2:15 AM
>>
>> 05/05/2020 10:59, Ferruh Yigit:
>>> On 5/5/2020 7:44 AM, Jerin Jacob wrote:
>>>> On Tue, May 5, 2020 at 8:39 AM Rasesh Mody <rmody at marvell.com>
>> wrote:
>>>>>
>>>>> Some applications do not explicitly restore Tx queues setup during
>>>>> port re-configuration. This patch adds changes to check for
>>>>> released Tx queues and restore the setup if application doesn't
>>>>> explicitly does that.
>>>>
>>>> +ethdev maintainers.
>>>>
>>>> I think, Ideally, the fix should be in common code if we need to
>>>> support such applications.
>>>
>>> Is this a case application re-configures to increase the number of
>>> queues but doesn't setup new queues?
>>> If so this looks like application error and application should be
>>> fixed instead of recover this in the ethdev.
>>
>> +1
>>
> 
> This is a case of KNI application performing device re-configuration to change MTU. The application explicitly calls Rx queue setup, however doesn't call Tx queue setup. When MTU for KNI interface is changed it runs into a segfault when trying to start Tx queues.

Why it crash? Device re-configuration should not be changing the number of the
queues, it is always 1. What is missing/wrong without the Tx queue setup?

> Some other applications make use of rte_eth_dev_set_mtu() ethdev op, which looks to be cleaner approach.
> 

+1. I don't know history if there is a specific reason this way selected, but
after release I think we can try this.