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Date: Mon, 12 Dec 2022 04:25:22 -0500 From: "Michael S. Tsirkin" <mst@...hat.com> To: Jason Wang <jasowang@...hat.com> Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH net] virtio-net: correctly enable callback during start_xmit On Mon, Dec 12, 2022 at 05:10:29PM +0800, Jason Wang wrote: > Commit a7766ef18b33("virtio_net: disable cb aggressively") enables > virtqueue callback via the following statement: > > do { > ...... > } while (use_napi && kick && > unlikely(!virtqueue_enable_cb_delayed(sq->vq))); > > This will cause a missing call to virtqueue_enable_cb_delayed() when > kick is false. Fixing this by removing the checking of the kick from > the condition to make sure callback is enabled correctly. > > Fixes: a7766ef18b33 ("virtio_net: disable cb aggressively") > Signed-off-by: Jason Wang <jasowang@...hat.com> > --- > The patch is needed for -stable. stable rules don't allow for theoretical fixes. Was a problem observed? > --- > drivers/net/virtio_net.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 86e52454b5b5..44d7daf0267b 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -1834,8 +1834,8 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) > > free_old_xmit_skbs(sq, false); > > - } while (use_napi && kick && > - unlikely(!virtqueue_enable_cb_delayed(sq->vq))); > + } while (use_napi && > + unlikely(!virtqueue_enable_cb_delayed(sq->vq))); > A bit more explanation pls. kick simply means !netdev_xmit_more - if it's false we know there will be another packet, then transmissing that packet will invoke virtqueue_enable_cb_delayed. No? > /* timestamp packet in software */ > skb_tx_timestamp(skb); > -- > 2.25.1
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