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virtio_ring: Avoid loop when vq is broken in virtqueue_poll

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[ Upstream commit 481a0d7422 ]

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.alibaba.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Mao Wenan 2020-08-02 15:44:09 +08:00 committed by Greg Kroah-Hartman
parent 9b5681afc9
commit 1f49e8cefa
1 changed files with 3 additions and 0 deletions
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3
drivers/virtio/virtio_ring.c
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@ -829,6 +829,9 @@ 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);
}