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Message-ID: <20170718225011-mutt-send-email-mst@kernel.org>
Date: Tue, 18 Jul 2017 23:07:42 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: virtualization@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 5/5] virtio-net: switch off offloads on demand
if possible on XDP set
On Mon, Jul 17, 2017 at 08:44:01PM +0800, Jason Wang wrote:
> Current XDP implementation want guest offloads feature to be disabled
s/want/wants/
> on qemu cli.
on the device.
> This is inconvenient and means guest can't benefit from
> offloads if XDP is not used. This patch tries to address this
> limitation by disable
disabling
> the offloads on demand through control guest
> offloads. Guest offloads will be disabled and enabled on demand on XDP
> set.
>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
In fact, since we no longer reset when XDP is set,
here device might have offloads enabled, buffers are
used but not consumed, then XDP is set.
This can result in
- packet scattered across multiple buffers
(handled correctly but need to update the comment)
- packet may have VIRTIO_NET_HDR_F_NEEDS_CSUM, in that case
the spec says "The checksum on the packet is incomplete".
(probably needs to be handled by calculating the checksum).
Ideas for follow-up patches:
- skip looking at packet data completely
won't work if you play with checksums dynamically
but can be done if disabled on device
- allow ethtools to tweak offloads from userspace as well
> ---
> drivers/net/virtio_net.c | 70 ++++++++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 65 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index e732bd6..d970c2d 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -57,6 +57,11 @@ DECLARE_EWMA(pkt_len, 0, 64)
>
> #define VIRTNET_DRIVER_VERSION "1.0.0"
>
> +const unsigned long guest_offloads[] = { VIRTIO_NET_F_GUEST_TSO4,
> + VIRTIO_NET_F_GUEST_TSO6,
> + VIRTIO_NET_F_GUEST_ECN,
> + VIRTIO_NET_F_GUEST_UFO };
> +
> struct virtnet_stats {
> struct u64_stats_sync tx_syncp;
> struct u64_stats_sync rx_syncp;
> @@ -164,10 +169,13 @@ struct virtnet_info {
> u8 ctrl_promisc;
> u8 ctrl_allmulti;
> u16 ctrl_vid;
> + u64 ctrl_offloads;
>
> /* Ethtool settings */
> u8 duplex;
> u32 speed;
> +
> + unsigned long guest_offloads;
> };
>
> struct padded_vnet_hdr {
> @@ -1889,6 +1897,47 @@ static int virtnet_restore_up(struct virtio_device *vdev)
> return err;
> }
>
> +static int virtnet_set_guest_offloads(struct virtnet_info *vi, u64 offloads)
> +{
> + struct scatterlist sg;
> + vi->ctrl_offloads = cpu_to_virtio64(vi->vdev, offloads);
> +
> + sg_init_one(&sg, &vi->ctrl_offloads, sizeof(vi->ctrl_offloads));
> +
> + if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_GUEST_OFFLOADS,
> + VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET, &sg)) {
> + dev_warn(&vi->dev->dev, "Fail to set guest offload. \n");
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static int virtnet_clear_guest_offloads(struct virtnet_info *vi)
> +{
> + u64 offloads = 0;
> +
> + if (!vi->guest_offloads)
> + return 0;
> +
> + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
> + offloads = 1ULL << VIRTIO_NET_F_GUEST_CSUM;
> +
> + return virtnet_set_guest_offloads(vi, offloads);
> +}
> +
> +static int virtnet_restore_guest_offloads(struct virtnet_info *vi)
> +{
> + u64 offloads = vi->guest_offloads;
> +
> + if (!vi->guest_offloads)
> + return 0;
> + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
> + offloads |= 1ULL << VIRTIO_NET_F_GUEST_CSUM;
> +
> + return virtnet_set_guest_offloads(vi, offloads);
> +}
> +
> static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
> struct netlink_ext_ack *extack)
> {
> @@ -1898,10 +1947,11 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
> u16 xdp_qp = 0, curr_qp;
> int i, err;
>
> - if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> - virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
> - virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
> - virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO)) {
> + if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)
> + && (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> + virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
> + virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
> + virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO))) {
> NL_SET_ERR_MSG_MOD(extack, "Can't set XDP while host is implementing LRO, disable LRO first");
> return -EOPNOTSUPP;
> }
> @@ -1950,6 +2000,12 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
> for (i = 0; i < vi->max_queue_pairs; i++) {
> old_prog = rtnl_dereference(vi->rq[i].xdp_prog);
> rcu_assign_pointer(vi->rq[i].xdp_prog, prog);
> + if (i == 0) {
> + if (!old_prog)
> + virtnet_clear_guest_offloads(vi);
> + if (!prog)
> + virtnet_restore_guest_offloads(vi);
> + }
> if (old_prog)
> bpf_prog_put(old_prog);
> napi_enable(&vi->rq[i].napi);
> @@ -2583,6 +2639,10 @@ static int virtnet_probe(struct virtio_device *vdev)
> netif_carrier_on(dev);
> }
>
> + for (i = 0; i < ARRAY_SIZE(guest_offloads); i++)
> + if (virtio_has_feature(vi->vdev, guest_offloads[i]))
> + set_bit(guest_offloads[i], &vi->guest_offloads);
> +
> pr_debug("virtnet: registered device %s with %d RX and TX vq's\n",
> dev->name, max_queue_pairs);
>
> @@ -2679,7 +2739,7 @@ static struct virtio_device_id id_table[] = {
> VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN, \
> VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, \
> VIRTIO_NET_F_CTRL_MAC_ADDR, \
> - VIRTIO_NET_F_MTU
> + VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS
>
> static unsigned int features[] = {
> VIRTNET_FEATURES,
> --
> 2.7.4
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