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: <20240516115942.GA443134@kernel.org>
Date: Thu, 16 May 2024 12:59:42 +0100
From: Simon Horman <horms@...nel.org>
To: Larysa Zaremba <larysa.zaremba@...el.com>
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 01:43:18PM +0200, Larysa Zaremba wrote:
> 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.
> > 
> > ...

Hi Larysa,

Thanks for your explanation, this all seems reasonable to me.

Reviewed-by: Simon Horman <horms@...nel.org>