netdev - Re: netif_set_xps_queue() before register_netdev(): correct from an API perspective?

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Date: Wed, 2 Aug 2023 09:42:57 -0700
From: Alexander Duyck <alexander.duyck@...il.com>
To: Vladimir Oltean <vladimir.oltean@....com>
Cc: Ioana Ciornei <ioana.ciornei@....com>, Antoine Tenart <atenart@...nel.org>, netdev@...r.kernel.org
Subject: Re: netif_set_xps_queue() before register_netdev(): correct from an
 API perspective?

On Wed, Aug 2, 2023 at 8:23 AM Vladimir Oltean <vladimir.oltean@....com> wrote:
>
> On Wed, Aug 02, 2023 at 08:04:01AM -0700, Alexander Duyck wrote:
> > We really shouldn't be calling it before the netdev is registered.
> >
> > That said though the easiest way to clean it up would probably be to
> > call netdev_reset_tc in case of a failure.
>
> Thanks. What else will happen that's bad with XPS being configured on
> TXQs of unregistered net devices? The call path has existed since 2017 -
> commit 93ddf0b211a0 ("staging: fsl-dpaa2/eth: Flow affinity for
> non-forwarded traffic").

The only risk I can think of would be the potential memory leak.

It might make sense to look at adding code to netif_free_tx_queues()
to free the XPS memory there if it hasn't been freed already. That
would resolve the memory leak issue and allow it to be used earlier.