On Mon, Dec 28, 2020 at 11:22:32AM -0500, Willem de Bruijn wrote:
> From: Willem de Bruijn <will...@google.com>
>
> Add optional PTP hardware timestamp offload for virtio-net.
>
> Accurate RTT measurement requires timestamps close to the wire.
> Introduce virtio feature VIRTIO_NET_F_RX_TSTAMP. If negotiated, the
> virtio-net header is expanded with room for a timestamp. A host may
> pass receive timestamps for all or some packets. A timestamp is valid
> if non-zero.
>
> The timestamp straddles (virtual) hardware domains. Like PTP, use
> international atomic time (CLOCK_TAI) as global clock base. It is
> guest responsibility to sync with host, e.g., through kvm-clock.
>
> Signed-off-by: Willem de Bruijn <will...@google.com>
> ---
> drivers/net/virtio_net.c | 20 +++++++++++++++++++-
> include/uapi/linux/virtio_net.h | 12 ++++++++++++
> 2 files changed, 31 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index b917b7333928..57744bb6a141 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -204,6 +204,9 @@ struct virtnet_info {
> /* Guest will pass tx path info to the host */
> bool has_tx_hash;
>
> + /* Host will pass CLOCK_TAI receive time to the guest */
> + bool has_rx_tstamp;
> +
> /* Has control virtqueue */
> bool has_cvq;
>
> @@ -292,6 +295,13 @@ static inline struct virtio_net_hdr_mrg_rxbuf
> *skb_vnet_hdr(struct sk_buff *skb)
> return (struct virtio_net_hdr_mrg_rxbuf *)skb->cb;
> }
>
> +static inline struct virtio_net_hdr_v12 *skb_vnet_hdr_12(struct sk_buff *skb)
> +{
> + BUILD_BUG_ON(sizeof(struct virtio_net_hdr_v12) > sizeof(skb->cb));
> +
> + return (void *)skb->cb;
> +}
> +
> /*
> * private is used to chain pages for big packets, put the whole
> * most recent used list in the beginning for reuse
> @@ -1082,6 +1092,9 @@ static void receive_buf(struct virtnet_info *vi, struct
> receive_queue *rq,
> goto frame_err;
> }
>
> + if (vi->has_rx_tstamp)
> + skb_hwtstamps(skb)->hwtstamp =
> ns_to_ktime(skb_vnet_hdr_12(skb)->tstamp);
> +
> skb_record_rx_queue(skb, vq2rxq(rq->vq));
> skb->protocol = eth_type_trans(skb, dev);
> pr_debug("Receiving skb proto 0x%04x len %i type %i\n",
> @@ -3071,6 +3084,11 @@ static int virtnet_probe(struct virtio_device *vdev)
> vi->hdr_len = sizeof(struct virtio_net_hdr_v1_hash);
> }
>
> + if (virtio_has_feature(vdev, VIRTIO_NET_F_RX_TSTAMP)) {
> + vi->has_rx_tstamp = true;
> + vi->hdr_len = sizeof(struct virtio_net_hdr_v12);
> + }
> +
> if (virtio_has_feature(vdev, VIRTIO_F_ANY_LAYOUT) ||
> virtio_has_feature(vdev, VIRTIO_F_VERSION_1))
> vi->any_header_sg = true;
> @@ -3261,7 +3279,7 @@ static struct virtio_device_id id_table[] = {
> VIRTIO_NET_F_CTRL_MAC_ADDR, \
> VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
> VIRTIO_NET_F_SPEED_DUPLEX, VIRTIO_NET_F_STANDBY, \
> - VIRTIO_NET_F_TX_HASH
> + VIRTIO_NET_F_TX_HASH, VIRTIO_NET_F_RX_TSTAMP
>
> static unsigned int features[] = {
> VIRTNET_FEATURES,
> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> index f6881b5b77ee..0ffe2eeebd4a 100644
> --- a/include/uapi/linux/virtio_net.h
> +++ b/include/uapi/linux/virtio_net.h
> @@ -57,6 +57,7 @@
> * Steering */
> #define VIRTIO_NET_F_CTRL_MAC_ADDR 23 /* Set MAC address */
>
> +#define VIRTIO_NET_F_RX_TSTAMP 55 /* Host sends TAI receive time
> */
> #define VIRTIO_NET_F_TX_HASH 56 /* Guest sends hash report */
> #define VIRTIO_NET_F_HASH_REPORT 57 /* Supports hash report */
> #define VIRTIO_NET_F_RSS 60 /* Supports RSS RX steering */
> @@ -182,6 +183,17 @@ struct virtio_net_hdr_v1_hash {
> };
> };
>
> +struct virtio_net_hdr_v12 {
> + struct virtio_net_hdr_v1 hdr;
> + struct {
> + __le32 value;
> + __le16 report;
> + __le16 flow_state;
> + } hash;
> + __virtio32 reserved;
Does endian-ness matter? If not - just u32?
> + __virtio64 tstamp;
> +};
> +
Given it's only available in modern devices, I think we
can make this __le64 tstamp.
> #ifndef VIRTIO_NET_NO_LEGACY
> /* This header comes first in the scatter-gather list.
> * For legacy virtio, if VIRTIO_F_ANY_LAYOUT is not negotiated, it must
> --
> 2.29.2.729.g45daf8777d-goog
