Willem de Bruijn
2021-Feb-02 22:17 UTC
[PATCH rfc 2/3] virtio-net: support receive timestamp
On Tue, Feb 2, 2021 at 9:08 AM 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> > > --- > > 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?I suppose it does not matter as long as this is reserved. Should it be __le32, at least?> > + __virtio64 tstamp; > > +}; > > + > > Given it's only available in modern devices, I think we > can make this __le64 tstamp.Actually, would it be possible to make new features available on legacy devices? There is nothing in the features bits precluding it. I have a revised patchset almost ready. I suppose I should send it as RFC again, and simultaneously file an OASIS ballot for each feature?
Michael S. Tsirkin
2021-Feb-02 23:02 UTC
[PATCH rfc 2/3] virtio-net: support receive timestamp
On Tue, Feb 02, 2021 at 05:17:13PM -0500, Willem de Bruijn wrote:> On Tue, Feb 2, 2021 at 9:08 AM 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> > > > --- > > > 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? > > I suppose it does not matter as long as this is reserved. Should it be > __le32, at least?One can safely assign 0 to any value.> > > + __virtio64 tstamp; > > > +}; > > > + > > > > Given it's only available in modern devices, I think we > > can make this __le64 tstamp. > > Actually, would it be possible to make new features available on > legacy devices? There is nothing in the features bits precluding it.I think it won't be possible: you are using feature bit 55, legacy devices have up to 32 feature bits. And of course the header looks a bit differently for legacy, you would have to add special code to handle that when mergeable buffers are off.> > I have a revised patchset almost ready. I suppose I should send it as > RFC again, and simultaneously file an OASIS ballot for each feature?that would be great. -- MST