On Wed, Apr 24, 2024 at 03:57:04AM -0700, Konstantin Ovsepian wrote:
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 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 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 (cherry picked from commit 059a49aa2e25c58f90b50151f109dd3c4cdb3a47) Signed-off-by: Konstantin Ovsepian ovs@ovs.to
drivers/net/virtio_net.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-)
Now queued up,t hanks.
greg k-h