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Message-ID: <65807512bc20b_805482941e@willemb.c.googlers.com.notmuch> Date: Mon, 18 Dec 2023 11:36:34 -0500 From: Willem de Bruijn <willemdebruijn.kernel@...il.com> To: Steffen Trumtrar <s.trumtrar@...gutronix.de>, "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Richard Cochran <richardcochran@...il.com> Cc: virtualization@...ts.linux.dev, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Willem de Bruijn <willemb@...gle.com> Subject: Re: [PATCH RFC 0/4] virtio-net: add tx-hash, rx-tstamp, tx-tstamp and tx-time 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@...il.com > Subject: [PATCH RFC v2 0/4] virtio-net: add tx-hash, rx-tstamp, > tx-tstamp and tx-time > From: Willem de Bruijn <willemb@...gle.com> > > 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@...gutronix.de> 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.
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