From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Fastabend Subject: [net PATCH 1/2] virtio_net: cap mtu when XDP programs are running Date: Wed, 04 Jan 2017 19:11:18 -0800 Message-ID: <20170105031118.2636.82374.stgit@john-Precision-Tower-5810> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: john.r.fastabend@intel.com, netdev@vger.kernel.org, john.fastabend@gmail.com To: jasowang@redhat.com, mst@redhat.com Return-path: Received: from mail-pg0-f66.google.com ([74.125.83.66]:34150 "EHLO mail-pg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932115AbdAEDLz (ORCPT ); Wed, 4 Jan 2017 22:11:55 -0500 Received: by mail-pg0-f66.google.com with SMTP id b1so39121334pgc.1 for ; Wed, 04 Jan 2017 19:11:36 -0800 (PST) Sender: netdev-owner@vger.kernel.org List-ID: XDP programs can not consume multiple pages so we cap the MTU to avoid this case. Virtio-net however only checks the MTU at XDP program load and does not block MTU changes after the program has loaded. This patch sets/clears the max_mtu value at XDP load/unload time. Signed-off-by: John Fastabend --- drivers/net/virtio_net.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 4a10500..261103d9 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1699,11 +1699,28 @@ static void virtnet_init_settings(struct net_device *dev) .set_settings = virtnet_set_settings, }; +#define MIN_MTU ETH_MIN_MTU +#define MAX_MTU ETH_MAX_MTU + +static unsigned long int virtnet_xdp_mtu(struct bpf_prog *prog, + struct virtnet_info *vi) +{ + if (!prog && virtio_has_feature(vi->vdev, VIRTIO_NET_F_MTU)) + return virtio_cread16(vi->vdev, + offsetof(struct virtio_net_config, mtu)); + else if (!prog) + return ETH_MAX_MTU; + else if (vi->mergeable_rx_bufs) + return PAGE_SIZE - sizeof(struct padded_vnet_hdr); + else + return GOOD_PACKET_LEN; +} + static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog) { - unsigned long int max_sz = PAGE_SIZE - sizeof(struct padded_vnet_hdr); struct virtnet_info *vi = netdev_priv(dev); struct bpf_prog *old_prog; + unsigned long int max_sz; u16 xdp_qp = 0, curr_qp; int i, err; @@ -1720,6 +1737,7 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog) return -EINVAL; } + max_sz = virtnet_xdp_mtu(prog, vi); if (dev->mtu > max_sz) { netdev_warn(dev, "XDP requires MTU less than %lu\n", max_sz); return -EINVAL; @@ -1748,6 +1766,9 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog) virtnet_set_queues(vi, curr_qp); return PTR_ERR(prog); } + dev->max_mtu = max_sz; + } else { + dev->max_mtu = ETH_MAX_MTU; } vi->xdp_queue_pairs = xdp_qp; @@ -2133,9 +2154,6 @@ static bool virtnet_validate_features(struct virtio_device *vdev) return true; } -#define MIN_MTU ETH_MIN_MTU -#define MAX_MTU ETH_MAX_MTU - static int virtnet_probe(struct virtio_device *vdev) { int i, err;