From 9b9cd8024a2882e896c65222aa421d461354e3f2 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Thu, 4 Jul 2013 11:22:57 +0930 Subject: virtio-net: fix the race between channels setting and refill Commit 55257d72bd1c51f25106350f4983ec19f62ed1fa (virtio-net: fill only rx queues which are being used) tries to refill on demand when changing the number of channels by call try_refill_recv() directly, this may race: - the refill work who may do the refill in the same time - the try_refill_recv() called in bh since napi was not disabled Which may led guest complain during setting channels: virtio_net virtio0: input.1:id 0 is not a head! Solve this issue by scheduling a refill work which can guarantee the serialization of refill. Cc: Sasha Levin Cc: Rusty Russell Cc: Michael S. Tsirkin Signed-off-by: Jason Wang Signed-off-by: Rusty Russell --- drivers/net/virtio_net.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) (limited to 'drivers/net/virtio_net.c') diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 655bb25eed2..6ddd77ece5d 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -900,7 +900,6 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs) struct scatterlist sg; struct virtio_net_ctrl_mq s; struct net_device *dev = vi->dev; - int i; if (!vi->has_cvq || !virtio_has_feature(vi->vdev, VIRTIO_NET_F_MQ)) return 0; @@ -914,10 +913,8 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs) queue_pairs); return -EINVAL; } else { - for (i = vi->curr_queue_pairs; i < queue_pairs; i++) - if (!try_fill_recv(&vi->rq[i], GFP_KERNEL)) - schedule_delayed_work(&vi->refill, 0); vi->curr_queue_pairs = queue_pairs; + schedule_delayed_work(&vi->refill, 0); } return 0; -- cgit v1.2.3-70-g09d2 From cbdadbbf0c790f79350a8f36029208944c5487d0 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Tue, 9 Jul 2013 08:13:04 +0300 Subject: virtio_net: fix race in RX VQ processing virtio net called virtqueue_enable_cq on RX path after napi_complete, so with NAPI_STATE_SCHED clear - outside the implicit napi lock. This violates the requirement to synchronize virtqueue_enable_cq wrt virtqueue_add_buf. In particular, used event can move backwards, causing us to lose interrupts. In a debug build, this can trigger panic within START_USE. Jason Wang reports that he can trigger the races artificially, by adding udelay() in virtqueue_enable_cb() after virtio_mb(). However, we must call napi_complete to clear NAPI_STATE_SCHED before polling the virtqueue for used buffers, otherwise napi_schedule_prep in a callback will fail, causing us to lose RX events. To fix, call virtqueue_enable_cb_prepare with NAPI_STATE_SCHED set (under napi lock), later call virtqueue_poll with NAPI_STATE_SCHED clear (outside the lock). Reported-by: Jason Wang Tested-by: Jason Wang Acked-by: Jason Wang Signed-off-by: Michael S. Tsirkin Signed-off-by: David S. Miller --- drivers/net/virtio_net.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'drivers/net/virtio_net.c') diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index c9e00387d99..42d670a468f 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -602,7 +602,7 @@ static int virtnet_poll(struct napi_struct *napi, int budget) container_of(napi, struct receive_queue, napi); struct virtnet_info *vi = rq->vq->vdev->priv; void *buf; - unsigned int len, received = 0; + unsigned int r, len, received = 0; again: while (received < budget && @@ -619,8 +619,9 @@ again: /* Out of packets? */ if (received < budget) { + r = virtqueue_enable_cb_prepare(rq->vq); napi_complete(napi); - if (unlikely(!virtqueue_enable_cb(rq->vq)) && + if (unlikely(virtqueue_poll(rq->vq, r)) && napi_schedule_prep(napi)) { virtqueue_disable_cb(rq->vq); __napi_schedule(napi); -- cgit v1.2.3-70-g09d2