From: Mao Wenan wenan.mao@linux.alibaba.com
stable inclusion from linux-4.19.142 commit 9f489d30979bd352ffbd555020b6ca79efb93b89
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[ Upstream commit 481a0d7422db26fb63e2d64f0652667a5c6d0f3e ]
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@linux.alibaba.com Acked-by: Michael S. Tsirkin mst@redhat.com Link: https://lore.kernel.org/r/1596354249-96204-1-git-send-email-wenan.mao@linux.... Signed-off-by: Michael S. Tsirkin mst@redhat.com Acked-by: Jason Wang jasowang@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yang Yingliang yangyingliang@huawei.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 6228b48d1e12..df7980aef927 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -828,6 +828,9 @@ 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 (u16)last_used_idx != virtio16_to_cpu(_vq->vdev, vq->vring.used->idx); }