From: Breno Leitao leitao@debian.org
commit 059a49aa2e25c58f90b50151f109dd3c4cdb3a47 upstream.
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 Reviewed-by: Heng Qi hengqi@linux.alibaba.com Reviewed-by: Xuan Zhuo xuanzhuo@linux.alibaba.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Vlad Poenaru vlad.wing@gmail.com --- drivers/net/virtio_net.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 7cb0548d17a3..56cbe00126bb 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -3570,19 +3570,34 @@ static int virtnet_get_rxfh(struct net_device *dev, u32 *indir, u8 *key, u8 *hfu static int virtnet_set_rxfh(struct net_device *dev, const u32 *indir, const u8 *key, const u8 hfunc) { struct virtnet_info *vi = netdev_priv(dev); + bool update = false; int i;
if (hfunc != ETH_RSS_HASH_NO_CHANGE && hfunc != ETH_RSS_HASH_TOP) return -EOPNOTSUPP;
if (indir) { + if (!vi->has_rss) + return -EOPNOTSUPP; + for (i = 0; i < vi->rss_indir_table_size; ++i) vi->ctrl->rss.indirection_table[i] = indir[i]; + update = true; } - if (key) + if (key) { + /* If either _F_HASH_REPORT or _F_RSS are negotiated, the + * device provides hash calculation capabilities, that is, + * hash_key is configured. + */ + if (!vi->has_rss && !vi->has_rss_hash_report) + return -EOPNOTSUPP; + memcpy(vi->ctrl->rss.key, key, vi->rss_key_size); + update = true; + }
- virtnet_commit_rss_command(vi); + if (update) + virtnet_commit_rss_command(vi);
return 0; } @@ -4491,13 +4506,15 @@ static int virtnet_probe(struct virtio_device *vdev) if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT)) vi->has_rss_hash_report = true;
- if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS)) + if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS)) { vi->has_rss = true;
- if (vi->has_rss || vi->has_rss_hash_report) { vi->rss_indir_table_size = virtio_cread16(vdev, offsetof(struct virtio_net_config, rss_max_indirection_table_length)); + } + + if (vi->has_rss || vi->has_rss_hash_report) { vi->rss_key_size = virtio_cread8(vdev, offsetof(struct virtio_net_config, rss_max_key_size));