Michael S. Tsirkin
2020-Dec-28 17:28 UTC
[PATCH rfc 2/3] virtio-net: support receive timestamp
On Mon, Dec 28, 2020 at 11:22:32AM -0500, Willem de Bruijn wrote:> From: Willem de Bruijn <willemb at 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 <willemb at 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; > + __virtio64 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 mustSo it looks like VIRTIO_NET_F_RX_TSTAMP should depend on both VIRTIO_NET_F_RX_TSTAMP and VIRTIO_NET_F_HASH_REPORT then? I am not sure what does v12 mean here. virtio_net_hdr_v1 is just with VIRTIO_F_VERSION_1, virtio_net_hdr_v1_hash is with VIRTIO_F_VERSION_1 and VIRTIO_NET_F_HASH_REPORT. So this one is virtio_net_hdr_hash_tstamp I guess?> -- > 2.29.2.729.g45daf8777d-goog
Willem de Bruijn
2020-Dec-28 19:30 UTC
[PATCH rfc 2/3] virtio-net: support receive timestamp
On Mon, Dec 28, 2020 at 12:29 PM Michael S. Tsirkin <mst at redhat.com> wrote:> > On Mon, Dec 28, 2020 at 11:22:32AM -0500, Willem de Bruijn wrote: > > From: Willem de Bruijn <willemb at 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 <willemb at google.com> > > 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; > > + __virtio64 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 > > > So it looks like VIRTIO_NET_F_RX_TSTAMP should depend on both > VIRTIO_NET_F_RX_TSTAMP and VIRTIO_NET_F_HASH_REPORT then?Do you mean VIRTIO_NET_F_TX_TSTAMP depends on VIRTIO_NET_F_RX_TSTAMP? I think if either is enabled we need to enable the extended layout. Regardless of whether TX_HASH or HASH_REPORT are enabled. If they are not, then those fields are ignored.> I am not sure what does v12 mean here. > > virtio_net_hdr_v1 is just with VIRTIO_F_VERSION_1, > virtio_net_hdr_v1_hash is with VIRTIO_F_VERSION_1 and > VIRTIO_NET_F_HASH_REPORT. > > So this one is virtio_net_hdr_hash_tstamp I guess?Sounds better, yes, will change that. This was an attempt at identifying the layout with the likely next generation of the spec, 1.2. Similar to virtio_net_hdr_v1. But that is both premature and not very helpful.