Steffen Trumtrar wrote: > This series tries to pick up the work on the virtio-net timestamping > feature from Willem de Bruijn. > > Original series > Message-Id: 20210208185558.995292-1-willemdebruijn.kernel@xxxxxxxxx > Subject: [PATCH RFC v2 0/4] virtio-net: add tx-hash, rx-tstamp, > tx-tstamp and tx-time > From: Willem de Bruijn <willemb@xxxxxxxxxx> > > RFC for four new features to the virtio network device: > > 1. pass tx flow state to host, for routing + telemetry > 2. pass rx tstamp to guest, for better RTT estimation > 3. pass tx tstamp to guest, idem > 3. pass tx delivery time to host, for accurate pacing > > All would introduce an extension to the virtio spec. > > The original series consisted of a hack around the DMA API, which should > be fixed in this series. > > The changes in this series are to the driver side. For the changes to qemu see: > https://github.com/strumtrar/qemu/tree/v8.1.1/virtio-net-ptp > > Currently only virtio-net is supported. The original series used > vhost-net as backend. However, the path through tun via sendmsg doesn't > allow us to write data back to the driver side without any hacks. > Therefore use the way via plain virtio-net without vhost albeit better > performance. > > Signed-off-by: Steffen Trumtrar <s.trumtrar@xxxxxxxxxxxxxx> Thanks for picking this back up, Steffen. Nice to see that the code still applies mostly cleanly. For context: I dropped the work only because I had no real device implementation. The referenced patch series to qemu changes that. I suppose the main issue is the virtio API changes that this introduces, which will have to be accepted to the spec. One small comment to patch 4: there I just assumed the virtual device time is CLOCK_TAI. There is a concurrent feature under review for HW pacing offload with AF_XDP sockets. The clock issue comes up a bit. In general, for hardware we cannot assume a clock. For virtio, perhaps assuming the same monotonic hardware clock in guest and host can be assumed. But this clock alignment needs some thought.
