| Message ID | 20240326151911.2155689-2-leitao@debian.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net,v2,1/2] virtio_net: Do not set rss_indir if RSS is not supported | expand |
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;
On Wed, Mar 27, 2024 at 10:27:58AM +0800, Heng Qi wrote: > > > 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. Sure, that works for me. Let me update it in v2.
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; + if (rxfh->hfunc != ETH_RSS_HASH_NO_CHANGE && rxfh->hfunc != ETH_RSS_HASH_TOP) return -EOPNOTSUPP;
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(+)