| Message ID | 151913354012.28247.1462800242440559823.stgit@firesoul |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net,1/4] virtio_net: disable XDP_REDIRECT in receive_mergeable() case | expand |
On 02/20/2018 05:32 AM, Jesper Dangaard Brouer wrote: > When a driver implements the ndo_xdp_xmit() function, there is > (currently) no generic way to determine whether it is safe to call. > > It is e.g. unsafe to call the drivers ndo_xdp_xmit, if it have not > allocated the needed XDP TX queues yet. This is the case for > virtio_net, which first allocates the XDP TX queues once an XDP/bpf > prog is attached (in virtnet_xdp_set()). > > Thus, a crash will occur for virtio_net when redirecting to another > virtio_net device's ndo_xdp_xmit, which have not attached a XDP prog. > The sample xdp_redirect_map tries to attach a dummy XDP prog to take > this into account, but it can also easily fail if the virtio_net (or > actually underlying vhost driver) have not allocated enough extra > queues for the device. > > Allocating more queue this is currently a manual config. > Hint for libvirt XML add: > > <driver name='vhost' queues='16'> > <host mrg_rxbuf='off'/> > <guest tso4='off' tso6='off' ecn='off' ufo='off'/> > </driver> > > The solution in this patch is to check that the device have loaded an > XDP/bpf prog before proceeding. This is similar to the check > performed in driver ixgbe. > > Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> > --- Yep, nice catch. I caught this in ixgbe but didn't manage to pull it into virtio. Acked-by: John Fastabend <john.fastabend@gmail.com> > drivers/net/virtio_net.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 1e0e0fce3ab2..9bb9e562b893 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -452,8 +452,18 @@ static bool __virtnet_xdp_xmit(struct virtnet_info *vi, > static int virtnet_xdp_xmit(struct net_device *dev, struct xdp_buff *xdp) > { > struct virtnet_info *vi = netdev_priv(dev); > - bool sent = __virtnet_xdp_xmit(vi, xdp); > + struct receive_queue *rq = vi->rq; > + struct bpf_prog *xdp_prog; > + bool sent; > + > + /* Only allow ndo_xdp_xmit if XDP is loaded on dev, as this > + * indicate XDP resources have been successfully allocated. > + */ > + xdp_prog = rcu_dereference(rq->xdp_prog); > + if (!xdp_prog) > + return -ENXIO; > > + sent = __virtnet_xdp_xmit(vi, xdp); > if (!sent) > return -ENOSPC; > return 0; >
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 1e0e0fce3ab2..9bb9e562b893 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -452,8 +452,18 @@ static bool __virtnet_xdp_xmit(struct virtnet_info *vi, static int virtnet_xdp_xmit(struct net_device *dev, struct xdp_buff *xdp) { struct virtnet_info *vi = netdev_priv(dev); - bool sent = __virtnet_xdp_xmit(vi, xdp); + struct receive_queue *rq = vi->rq; + struct bpf_prog *xdp_prog; + bool sent; + + /* Only allow ndo_xdp_xmit if XDP is loaded on dev, as this + * indicate XDP resources have been successfully allocated. + */ + xdp_prog = rcu_dereference(rq->xdp_prog); + if (!xdp_prog) + return -ENXIO; + sent = __virtnet_xdp_xmit(vi, xdp); if (!sent) return -ENOSPC; return 0;
When a driver implements the ndo_xdp_xmit() function, there is (currently) no generic way to determine whether it is safe to call. It is e.g. unsafe to call the drivers ndo_xdp_xmit, if it have not allocated the needed XDP TX queues yet. This is the case for virtio_net, which first allocates the XDP TX queues once an XDP/bpf prog is attached (in virtnet_xdp_set()). Thus, a crash will occur for virtio_net when redirecting to another virtio_net device's ndo_xdp_xmit, which have not attached a XDP prog. The sample xdp_redirect_map tries to attach a dummy XDP prog to take this into account, but it can also easily fail if the virtio_net (or actually underlying vhost driver) have not allocated enough extra queues for the device. Allocating more queue this is currently a manual config. Hint for libvirt XML add: <driver name='vhost' queues='16'> <host mrg_rxbuf='off'/> <guest tso4='off' tso6='off' ecn='off' ufo='off'/> </driver> The solution in this patch is to check that the device have loaded an XDP/bpf prog before proceeding. This is similar to the check performed in driver ixgbe. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> --- drivers/net/virtio_net.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)