netdev - Re: [PATCH net v3] virtio_net: Fix error unwinding of XDP initialization

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Date: Mon, 8 May 2023 09:45:51 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: Feng Liu <feliu@...dia.com>
Cc: Jason Wang <jasowang@...hat.com>,
 "Michael S . Tsirkin" <mst@...hat.com>,
 Simon Horman <simon.horman@...igine.com>,
 Bodong Wang <bodong@...dia.com>,
 William Tu <witu@...dia.com>,
 Parav Pandit <parav@...dia.com>,
 virtualization@...ts.linux-foundation.org,
 netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 bpf@...r.kernel.org
Subject: Re: [PATCH net v3] virtio_net: Fix error unwinding of XDP initialization

On Sat, 6 May 2023 08:08:02 -0400, Feng Liu <feliu@...dia.com> wrote:
>
>
> On 2023-05-05 p.m.10:33, Xuan Zhuo wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > On Tue, 2 May 2023 20:35:25 -0400, Feng Liu <feliu@...dia.com> wrote:
> >> When initializing XDP in virtnet_open(), some rq xdp initialization
> >> may hit an error causing net device open failed. However, previous
> >> rqs have already initialized XDP and enabled NAPI, which is not the
> >> expected behavior. Need to roll back the previous rq initialization
> >> to avoid leaks in error unwinding of init code.
> >>
> >> Also extract a helper function of disable queue pairs, and use newly
> >> introduced helper function in error unwinding and virtnet_close;
> >>
> >> Issue: 3383038
> >> Fixes: 754b8a21a96d ("virtio_net: setup xdp_rxq_info")
> >> Signed-off-by: Feng Liu <feliu@...dia.com>
> >> Reviewed-by: William Tu <witu@...dia.com>
> >> Reviewed-by: Parav Pandit <parav@...dia.com>
> >> Reviewed-by: Simon Horman <simon.horman@...igine.com>
> >> Acked-by: Michael S. Tsirkin <mst@...hat.com>
> >> Change-Id: Ib4c6a97cb7b837cfa484c593dd43a435c47ea68f
> >> ---
> >>   drivers/net/virtio_net.c | 30 ++++++++++++++++++++----------
> >>   1 file changed, 20 insertions(+), 10 deletions(-)
> >>
> >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> >> index 8d8038538fc4..3737cf120cb7 100644
> >> --- a/drivers/net/virtio_net.c
> >> +++ b/drivers/net/virtio_net.c
> >> @@ -1868,6 +1868,13 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
> >>        return received;
> >>   }
> >>
> >> +static void virtnet_disable_qp(struct virtnet_info *vi, int qp_index)
> >> +{
> >> +     virtnet_napi_tx_disable(&vi->sq[qp_index].napi);
> >> +     napi_disable(&vi->rq[qp_index].napi);
> >> +     xdp_rxq_info_unreg(&vi->rq[qp_index].xdp_rxq);
> >> +}
> >> +
> >>   static int virtnet_open(struct net_device *dev)
> >>   {
> >>        struct virtnet_info *vi = netdev_priv(dev);
> >> @@ -1883,20 +1890,26 @@ static int virtnet_open(struct net_device *dev)
> >>
> >>                err = xdp_rxq_info_reg(&vi->rq[i].xdp_rxq, dev, i, vi->rq[i].napi.napi_id);
> >>                if (err < 0)
> >> -                     return err;
> >> +                     goto err_xdp_info_reg;
> >>
> >>                err = xdp_rxq_info_reg_mem_model(&vi->rq[i].xdp_rxq,
> >>                                                 MEM_TYPE_PAGE_SHARED, NULL);
> >> -             if (err < 0) {
> >> -                     xdp_rxq_info_unreg(&vi->rq[i].xdp_rxq);
> >> -                     return err;
> >> -             }
> >> +             if (err < 0)
> >> +                     goto err_xdp_reg_mem_model;
> >>
> >>                virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);
> >>                virtnet_napi_tx_enable(vi, vi->sq[i].vq, &vi->sq[i].napi);
> >>        }
> >>
> >>        return 0;
> >> +
> >> +err_xdp_reg_mem_model:
> >> +     xdp_rxq_info_unreg(&vi->rq[i].xdp_rxq);
> >> +err_xdp_info_reg:
> >> +     for (i = i - 1; i >= 0; i--)
> >> +             virtnet_disable_qp(vi, i);
> >
> >
> > I would to know should we handle for these:
> >
> >          disable_delayed_refill(vi);
> >          cancel_delayed_work_sync(&vi->refill);
> >
> >
> > Maybe we should call virtnet_close() with "i" directly.
> >
> > Thanks.
> >
> >
> Can’t use i directly here, because if xdp_rxq_info_reg fails, napi has
> not been enabled for current qp yet, I should roll back from the queue
> pairs where napi was enabled before(i--), otherwise it will hang at napi
> disable api

This is not the point, the key is whether we should handle with:

          disable_delayed_refill(vi);
          cancel_delayed_work_sync(&vi->refill);

Thanks.


>
> >> +
> >> +     return err;
> >>   }
> >>
> >>   static int virtnet_poll_tx(struct napi_struct *napi, int budget)
> >> @@ -2305,11 +2318,8 @@ static int virtnet_close(struct net_device *dev)
> >>        /* Make sure refill_work doesn't re-enable napi! */
> >>        cancel_delayed_work_sync(&vi->refill);
> >>
> >> -     for (i = 0; i < vi->max_queue_pairs; i++) {
> >> -             virtnet_napi_tx_disable(&vi->sq[i].napi);
> >> -             napi_disable(&vi->rq[i].napi);
> >> -             xdp_rxq_info_unreg(&vi->rq[i].xdp_rxq);
> >> -     }
> >> +     for (i = 0; i < vi->max_queue_pairs; i++)
> >> +             virtnet_disable_qp(vi, i);
> >>
> >>        return 0;
> >>   }
> >> --
> >> 2.37.1 (Apple Git-137.1)
> >>