On Mon, Nov 16, 2020 at 01:01:40PM +0100, Björn Töpel wrote: > > On 2020-11-16 12:55, Michael S. Tsirkin wrote: > > On Mon, Nov 16, 2020 at 12:04:12PM +0100, Björn Töpel wrote: > > > From: Björn Töpel <bjorn.topel@xxxxxxxxx> > > > > > > Add napi_id to the xdp_rxq_info structure, and make sure the XDP > > > socket pick up the napi_id in the Rx path. The napi_id is used to find > > > the corresponding NAPI structure for socket busy polling. > > > > > > Acked-by: Ilias Apalodimas <ilias.apalodimas@xxxxxxxxxx> > > > Signed-off-by: Björn Töpel <bjorn.topel@xxxxxxxxx> > > > > A bunch of drivers just pass in 0. could you explain when > > is that ok? how bad is it if the wrong id is used? > > > > If zero is passed, which is a non-valid NAPI_ID, busy-polling will never > be performed. > > Depending on the structure of the driver, napi might or might not be > initialized (napi_id != 0) or even available. When it wasn't obvious, I > simply set it to zero. > > So, short; No harm if zero, but busy-polling cannot be used in an XDP > context. > > > [...] > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > index 21b71148c532..d71fe41595b7 100644 > > > --- a/drivers/net/virtio_net.c > > > +++ b/drivers/net/virtio_net.c > > > @@ -1485,7 +1485,7 @@ static int virtnet_open(struct net_device *dev) > > > if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL)) > > > schedule_delayed_work(&vi->refill, 0); > > > - err = xdp_rxq_info_reg(&vi->rq[i].xdp_rxq, dev, i); > > > + err = xdp_rxq_info_reg(&vi->rq[i].xdp_rxq, dev, i, 0); > > > if (err < 0) > > > return err; > > > > Should this be rq.napi.napi_id ? > > > > Yes, if rq.napi.napi_id is valid here! Is it? What initializes it? netif_napi_add? Then I think yes, it's initialized for all queues ... Needs to be tested naturally. > > Cheers, > Björn
