在 2024/3/26 下午11:19, Breno Leitao 写道:

There is a bug when setting the RSS options in virtio_net that can break the whole machine, getting the kernel into an infinite loop.

Running the following command in any QEMU virtual machine with virtionet will reproduce this problem:

 # ethtool -X eth0  hfunc toeplitz

This is how the problem happens:

1. ethtool_set_rxfh() calls virtnet_set_rxfh()

2. virtnet_set_rxfh() calls virtnet_commit_rss_command()

3. virtnet_commit_rss_command() populates 4 entries for the rss

scatter-gather

4. Since the command above does not have a key, then the last

scatter-gatter entry will be zeroed, since rss_key_size == 0. sg_buf_size = vi->rss_key_size;

5. This buffer is passed to qemu, but qemu is not happy with a buffer

with zero length, and do the following in virtqueue_map_desc() (QEMU function):

if (!sz) { virtio_error(vdev, "virtio: zero sized buffers are not allowed");

6. virtio_error() (also QEMU function) set the device as broken

   vdev->broken = true;

7. Qemu bails out, and do not repond this crazy kernel.

8. The kernel is waiting for the response to come back (function

virtnet_send_command())

9. The kernel is waiting doing the following :

   while (!virtqueue_get_buf(vi->cvq, &tmp) &&
    !virtqueue_is_broken(vi->cvq))
     cpu_relax();
   
   

10. None of the following functions above is true, thus, the kernel

loops here forever. Keeping in mind that virtqueue_is_broken() does not look at the qemu `vdev->broken`, so, it never realizes that the vitio is broken at QEMU side.

Fix it by not sending RSS commands if the feature is not available in the device.

Fixes: c7114b1249fa ("drivers/net/virtio_net: Added basic RSS support.") Cc: stable@vger.kernel.org Cc: qemu-devel@nongnu.org Signed-off-by: Breno Leitao leitao@debian.org

---

drivers/net/virtio_net.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index c640fdf28fc5..e6b0eaf08ac2 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -3809,6 +3809,9 @@ static int virtnet_set_rxfh(struct net_device *dev, struct virtnet_info *vi = netdev_priv(dev); int i;

• if (!vi->has_rss && !vi->has_rss_hash_report)

• return -EOPNOTSUPP;
  

Why not make the second patch as the first, this seems to work better. Or squash them into one patch.

Apart from these and Xuan's comments.

For series:

Reviewed-by: Heng Qi hengqi@linux.alibaba.com

Regards, Heng

if (rxfh->hfunc != ETH_RSS_HASH_NO_CHANGE && rxfh->hfunc != ETH_RSS_HASH_TOP) return -EOPNOTSUPP;