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Date:   Mon, 18 Jul 2022 16:58:15 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        Vadim Pasternak <vadimp@...dia.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Cornelia Huck <cohuck@...hat.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Eric Farman <farman@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        linux-um@...ts.infradead.org, netdev <netdev@...r.kernel.org>,
        platform-driver-x86@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm <kvm@...r.kernel.org>,
        "open list:XDP (eXpress Data Path)" <bpf@...r.kernel.org>,
        kangjie.xu@...ux.alibaba.com,
        virtualization <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH v11 38/40] virtio_net: support rx queue resize

On Mon, 18 Jul 2022 16:56:24 +0800, Jason Wang <jasowang@...hat.com> wrote:
> On Fri, Jul 15, 2022 at 4:37 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> >
> > On Fri, 8 Jul 2022 14:20:52 +0800, Jason Wang <jasowang@...hat.com> wrote:
> > > On Tue, Jul 5, 2022 at 10:00 AM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> > > >
> > > > On Mon, 4 Jul 2022 11:44:12 +0800, Jason Wang <jasowang@...hat.com> wrote:
> > > > >
> > > > > 在 2022/6/29 14:56, Xuan Zhuo 写道:
> > > > > > This patch implements the resize function of the rx queues.
> > > > > > Based on this function, it is possible to modify the ring num of the
> > > > > > queue.
> > > > > >
> > > > > > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > > > > > ---
> > > > > >   drivers/net/virtio_net.c | 22 ++++++++++++++++++++++
> > > > > >   1 file changed, 22 insertions(+)
> > > > > >
> > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > > > index 9fe222a3663a..6ab16fd193e5 100644
> > > > > > --- a/drivers/net/virtio_net.c
> > > > > > +++ b/drivers/net/virtio_net.c
> > > > > > @@ -278,6 +278,8 @@ struct padded_vnet_hdr {
> > > > > >     char padding[12];
> > > > > >   };
> > > > > >
> > > > > > +static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf);
> > > > > > +
> > > > > >   static bool is_xdp_frame(void *ptr)
> > > > > >   {
> > > > > >     return (unsigned long)ptr & VIRTIO_XDP_FLAG;
> > > > > > @@ -1846,6 +1848,26 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
> > > > > >     return NETDEV_TX_OK;
> > > > > >   }
> > > > > >
> > > > > > +static int virtnet_rx_resize(struct virtnet_info *vi,
> > > > > > +                        struct receive_queue *rq, u32 ring_num)
> > > > > > +{
> > > > > > +   int err, qindex;
> > > > > > +
> > > > > > +   qindex = rq - vi->rq;
> > > > > > +
> > > > > > +   napi_disable(&rq->napi);
> > > > >
> > > > >
> > > > > Do we need to cancel the refill work here?
> > > >
> > > >
> > > > I think no, napi_disable is mutually exclusive, which ensures that there will be
> > > > no conflicts between them.
> > >
> > > So this sounds similar to what I've fixed recently.
> > >
> > > 1) NAPI schedule delayed work.
> > > 2) we disable NAPI here
> > > 3) delayed work get schedule and call NAPI again
> > >
> > > ?
> >
> > Yes, but I don't think there are any negative effects.
>
> An infinite wait on the napi_disable()?

Yes.

Thanks.


>
> Thanks
>
> >
> > Thanks.
> >
> > >
> > > Thanks
> > >
> > > >
> > > > Thanks.
> > > >
> > > > >
> > > > > Thanks
> > > > >
> > > > >
> > > > > > +
> > > > > > +   err = virtqueue_resize(rq->vq, ring_num, virtnet_rq_free_unused_buf);
> > > > > > +   if (err)
> > > > > > +           netdev_err(vi->dev, "resize rx fail: rx queue index: %d err: %d\n", qindex, err);
> > > > > > +
> > > > > > +   if (!try_fill_recv(vi, rq, GFP_KERNEL))
> > > > > > +           schedule_delayed_work(&vi->refill, 0);
> > > > > > +
> > > > > > +   virtnet_napi_enable(rq->vq, &rq->napi);
> > > > > > +   return err;
> > > > > > +}
> > > > > > +
> > > > > >   /*
> > > > > >    * Send command via the control virtqueue and check status.  Commands
> > > > > >    * supported by the hypervisor, as indicated by feature bits, should
> > > > >
> > > >
> > >
> >
>

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