netdev - Re: [PATCH 4/6] virtio_net: allow specifying context for rx

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Date:   Thu, 30 Mar 2017 17:31:37 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Cornelia Huck <cornelia.huck@...ibm.com>
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        John Fastabend <john.fastabend@...il.com>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 4/6] virtio_net: allow specifying context for rx

On Thu, Mar 30, 2017 at 09:26:51AM +0200, Cornelia Huck wrote:
> On Wed, 29 Mar 2017 23:48:54 +0300
> "Michael S. Tsirkin" <mst@...hat.com> wrote:
> 
> > With mergeable buffers we never use s/g for rx,
> > so allow specifying context in that case.
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> > ---
> >  drivers/net/virtio_net.c | 15 ++++++++++++++-
> >  1 file changed, 14 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 6802169..340f737 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -2044,6 +2044,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> >  	int ret = -ENOMEM;
> >  	int i, total_vqs;
> >  	const char **names;
> > +	const bool *ctx;
> >  
> >  	/* We expect 1 RX virtqueue followed by 1 TX virtqueue, followed by
> >  	 * possible N-1 RX/TX queue pairs used in multiqueue mode, followed by
> > @@ -2062,6 +2063,13 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> >  	names = kmalloc(total_vqs * sizeof(*names), GFP_KERNEL);
> >  	if (!names)
> >  		goto err_names;
> > +	if (vi->mergeable_rx_bufs) {
> > +		ctx = kzalloc(total_vqs * sizeof(*ctx), GFP_KERNEL);
> > +		if (!ctx)
> > +			goto err_ctx;
> > +	} else {
> > +		ctx = NULL;
> > +	}
> >  
> >  	/* Parameters for control virtqueue, if any */
> >  	if (vi->has_cvq) {
> > @@ -2077,9 +2085,12 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> >  		sprintf(vi->sq[i].name, "output.%d", i);
> >  		names[rxq2vq(i)] = vi->rq[i].name;
> >  		names[txq2vq(i)] = vi->sq[i].name;
> > +		if (ctx)
> > +			ctx[rxq2vq(i)] = true;
> >  	}
> >  
> > -	ret = virtio_find_vqs(vi->vdev, total_vqs, vqs, callbacks, names, NULL);
> > +	ret = vi->vdev->config->find_vqs(vi->vdev, total_vqs, vqs, callbacks,
> > +					 names, ctx, NULL);
> 
> virtio_find_vqs_ctx()? (Needs to be exported, obviously.)

I guess I can do that but there's a single user ATM.
Do you think it's worth doing right now, or wait until
it gets more users?


> >  	if (ret)
> >  		goto err_find;
> >  
> > @@ -2101,6 +2112,8 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> >  	return 0;
> >  
> >  err_find:
> > +	kfree(ctx);
> > +err_ctx:
> >  	kfree(names);
> >  err_names:
> >  	kfree(callbacks);