linux-kernel - Re: [RFC net-next v3 2/4] virtio_net: Prepare for NAPI to queue mapping

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Message-ID: <Z5Gtve0NoZwPNP4A@LQ3V64L9R2>
Date: Wed, 22 Jan 2025 18:47:25 -0800
From: Joe Damato <jdamato@...tly.com>
To: Jason Wang <jasowang@...hat.com>
Cc: netdev@...r.kernel.org, gerhard@...leder-embedded.com,
	leiyang@...hat.com, xuanzhuo@...ux.alibaba.com,
	mkarsten@...terloo.ca, "Michael S. Tsirkin" <mst@...hat.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	"open list:VIRTIO CORE AND NET DRIVERS" <virtualization@...ts.linux.dev>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC net-next v3 2/4] virtio_net: Prepare for NAPI to queue
 mapping

On Thu, Jan 23, 2025 at 10:40:43AM +0800, Jason Wang wrote:
> On Thu, Jan 23, 2025 at 1:41 AM Joe Damato <jdamato@...tly.com> wrote:
> >
> > On Wed, Jan 22, 2025 at 02:12:46PM +0800, Jason Wang wrote:
> > > On Wed, Jan 22, 2025 at 3:11 AM Joe Damato <jdamato@...tly.com> wrote:
> > > >
> > > > Slight refactor to prepare the code for NAPI to queue mapping. No
> > > > functional changes.
> > > >
> > > > Signed-off-by: Joe Damato <jdamato@...tly.com>
> > > > Reviewed-by: Gerhard Engleder <gerhard@...leder-embedded.com>
> > > > Tested-by: Lei Yang <leiyang@...hat.com>
> > > > ---
> > > >  v2:
> > > >    - Previously patch 1 in the v1.
> > > >    - Added Reviewed-by and Tested-by tags to commit message. No
> > > >      functional changes.
> > > >
> > > >  drivers/net/virtio_net.c | 10 ++++++++--
> > > >  1 file changed, 8 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > index 7646ddd9bef7..cff18c66b54a 100644
> > > > --- a/drivers/net/virtio_net.c
> > > > +++ b/drivers/net/virtio_net.c
> > > > @@ -2789,7 +2789,8 @@ static void skb_recv_done(struct virtqueue *rvq)
> > > >         virtqueue_napi_schedule(&rq->napi, rvq);
> > > >  }
> > > >
> > > > -static void virtnet_napi_enable(struct virtqueue *vq, struct napi_struct *napi)
> > > > +static void virtnet_napi_do_enable(struct virtqueue *vq,
> > > > +                                  struct napi_struct *napi)
> > > >  {
> > > >         napi_enable(napi);
> > >
> > > Nit: it might be better to not have this helper to avoid a misuse of
> > > this function directly.
> >
> > Sorry, I'm probably missing something here.
> >
> > Both virtnet_napi_enable and virtnet_napi_tx_enable need the logic
> > in virtnet_napi_do_enable.
> >
> > Are you suggesting that I remove virtnet_napi_do_enable and repeat
> > the block of code in there twice (in virtnet_napi_enable and
> > virtnet_napi_tx_enable)?
> 
> I think I miss something here, it looks like virtnet_napi_tx_enable()
> calls virtnet_napi_do_enable() directly.
> 
> I would like to know why we don't call netif_queue_set_napi() for TX NAPI here?

Please see both the cover letter and the commit message of the next
commit which addresses this question.

TX-only NAPIs do not have NAPI IDs so there is nothing to map.