在 2024/4/1 上午4:20, Michael S. Tsirkin 写道:
On Fri, Mar 29, 2024 at 10:16:41AM -0700, Breno Leitao wrote:
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 toeplitzThis is how the problem happens:
ethtool_set_rxfh() calls virtnet_set_rxfh()
virtnet_set_rxfh() calls virtnet_commit_rss_command()
virtnet_commit_rss_command() populates 4 entries for the rss
scatter-gather
- 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;
- 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");
virtio_error() (also QEMU function) set the device as broken
vdev->broken = true;
Qemu bails out, and do not repond this crazy kernel.
The kernel is waiting for the response to come back (function
virtnet_send_command())
The kernel is waiting doing the following :
while (!virtqueue_get_buf(vi->cvq, &tmp) && !virtqueue_is_broken(vi->cvq)) cpu_relax();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
net has its own stable process, don't CC stable on net patches.
Cc: qemu-devel@nongnu.org Signed-off-by: Breno Leitao leitao@debian.org
Changelog:
V2:
- Moved from creating a valid packet, by rejecting the request completely
V3:
- Got some good feedback from and Xuan Zhuo and Heng Qi, and reworked the rejection path.
drivers/net/virtio_net.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index c22d1118a133..c4a21ec51adf 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -3807,6 +3807,7 @@ static int virtnet_set_rxfh(struct net_device *dev, struct netlink_ext_ack *extack) { struct virtnet_info *vi = netdev_priv(dev);
- bool update = false; int i;
if (rxfh->hfunc != ETH_RSS_HASH_NO_CHANGE && @@ -3814,13 +3815,24 @@ static int virtnet_set_rxfh(struct net_device *dev, return -EOPNOTSUPP; if (rxfh->indir) {
if (!vi->has_rss)return -EOPNOTSUPP;- for (i = 0; i < vi->rss_indir_table_size; ++i) vi->ctrl->rss.indirection_table[i] = rxfh->indir[i];
update = true;
- if (rxfh->key)
- if (rxfh->key) {
if (!vi->has_rss && !vi->has_rss_hash_report)return -EOPNOTSUPP;What's the logic here? Is it || or &&? A comment can't hurt.
&&
Hi Breno,
You can add a comment like the following:
If either _F_HASH_REPORT or _F_RSS are negotiated, the device provides hash calculation capabilities, that is, hash_key can be configured.
Regards, Heng
- memcpy(vi->ctrl->rss.key, rxfh->key, vi->rss_key_size);
update = true;- }
- virtnet_commit_rss_command(vi);
- if (update)
virtnet_commit_rss_command(vi);return 0; } @@ -4729,13 +4741,15 @@ 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));
2.43.0