From: Willem de Bruijn <willemb@xxxxxxxxxx>
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@xxxxxxxxxx>
---
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 must
--
2.29.2.729.g45daf8777d-goog
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