netdev - Re: [PATCH iwl-net 3/3] ice: map XDP queues to vectors in ice_vsi_map_rings_to

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Message-ID: <ZkXxVp3hFvczWr8r@lzaremba-mobl.ger.corp.intel.com>
Date: Thu, 16 May 2024 13:43:18 +0200
From: Larysa Zaremba <larysa.zaremba@...el.com>
To: Simon Horman <horms@...nel.org>
CC: <intel-wired-lan@...ts.osuosl.org>, Jacob Keller
	<jacob.e.keller@...el.com>, <maciej.fijalkowski@...el.com>, Magnus Karlsson
	<magnus.karlsson@...il.com>, Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	<igor.bagnucki@...el.com>, "David S. Miller" <davem@...emloft.net>, "Eric
 Dumazet" <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
	<daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, "John
 Fastabend" <john.fastabend@...il.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>
Subject: Re: [PATCH iwl-net 3/3] ice: map XDP queues to vectors in
 ice_vsi_map_rings_to_vectors()

On Thu, May 16, 2024 at 09:27:13AM +0100, Simon Horman wrote:
> On Wed, May 15, 2024 at 06:02:16PM +0200, Larysa Zaremba wrote:
> > ice_pf_dcb_recfg() re-maps queues to vectors with
> > ice_vsi_map_rings_to_vectors(), which does not restore the previous
> > state for XDP queues. This leads to no AF_XDP traffic after rebuild.
> > 
> > Map XDP queues to vectors in ice_vsi_map_rings_to_vectors().
> > Also, move the code around, so XDP queues are mapped independently only
> > through .ndo_bpf().
> 
> Hi Larysa,
> 
> I take it the last sentence refers to the placement of ice_map_xdp_rings()
> in ice_prepare_xdp_rings() after rather than before the
> (cfg_type == ICE_XDP_CFG_PART) condition.
> 
> If so, I see that it is a small change. But I do wonder if it is separate
> from fixing the issue described in the first paragraph. And thus would
> be better as a separate patch.

This is not neccessary for the fix to work, but I think this is intergral to
making the change properly. I mean, before the change in the rebuild path we map
XDP rings to vectors only once and after the change we do this only once, just
previously it was in ice_prepare_xdp_rings() and now it is in
ice_vsi_map_rings_to_vectors().

> 
> Also, (I'm raising a separate issue :) breaking out logic into
> ice_xdp_ring_from_qid() seems very nice.  But I wonder if this ought to be
> part of a cleanup-patch for 'iwl' rather than a fixes patch for 'iwl-next'.
>

I have separated this into a separate function, because 2 lines exceeded 80 
characters, which is not in line with our current style for drivers.
And I do not think that this small function creates any more additional 
potentian applying problems for this patch. And the change is small enough to 
see that the logic stays the same.

> OTOH, I do see that breaking out ice_map_xdp_rings() makes sense in the
> context of this fix as the same logic is to be called in two places.
> 
> Splitting patches aside, the resulting code looks good to me.
> 
> ...
>