Jason Wang
2020-Aug-04 02:42 UTC
[PATCH -next v3] virtio_ring: Avoid loop when vq is broken in virtqueue_poll
On 2020/8/2 ??3:44, Mao Wenan wrote:> The loop may exist if vq->broken is true, > virtqueue_get_buf_ctx_packed or virtqueue_get_buf_ctx_split > will return NULL, so virtnet_poll will reschedule napi to > receive packet, it will lead cpu usage(si) to 100%. > > call trace as below: > virtnet_poll > virtnet_receive > virtqueue_get_buf_ctx > virtqueue_get_buf_ctx_packed > virtqueue_get_buf_ctx_split > virtqueue_napi_complete > virtqueue_poll //return true > virtqueue_napi_schedule //it will reschedule napi > > to fix this, return false if vq is broken in virtqueue_poll. > > Signed-off-by: Mao Wenan <wenan.mao at linux.alibaba.com> > Acked-by: Michael S. Tsirkin <mst at redhat.com> > --- > v2->v3: change subject, original is : "virtio_net: Avoid loop in virtnet_poll" > v1->v2: fix it in virtqueue_poll suggested by Michael S. Tsirkin <mst at redhat.com> > drivers/virtio/virtio_ring.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index 58b96ba..4f7c73e 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -1960,6 +1960,9 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx) > { > struct vring_virtqueue *vq = to_vvq(_vq); > > + if (unlikely(vq->broken)) > + return false; > + > virtio_mb(vq->weak_barriers); > return vq->packed_ring ? virtqueue_poll_packed(_vq, last_used_idx) : > virtqueue_poll_split(_vq, last_used_idx);Acked-by: Jason Wang <jasowang at redhat.com>