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@xxxxxxxxxx> wrote:
> >
> > On Mon, Dec 28, 2020 at 11:22:32AM -0500, Willem de Bruijn wrote:
> > > 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;
> >
> >
> > 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
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