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Date: Wed, 19 Jul 2017 10:39:53 +0800
From: Jason Wang <jasowang@...hat.com>
To: "Michael S. Tsirkin" <mst@...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 2017年07月19日 04:07, Michael S. Tsirkin wrote:
> 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)
Ok.
> - 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).
That's an option. Maybe it's tricky but I was thinking whether or not we
can just keep the CHECKSUM_PARTIAL here.
>
>
> 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
Right.
Thanks
>
>> ---
>> 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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