From: "Michael S. Tsirkin" <mst@redhat.com>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: Network Development <netdev@vger.kernel.org>,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH rfc 2/3] virtio-net: support receive timestamp
Date: Mon, 28 Dec 2020 16:32:48 -0500 [thread overview]
Message-ID: <20201228162903-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CA+FuTScguDWkvk=Lc+GzP=UCK2wjRFNJ_GEn_bniHpCDWdkfjg@mail.gmail.com>
On Mon, Dec 28, 2020 at 02:30:31PM -0500, Willem de Bruijn wrote:
> On Mon, Dec 28, 2020 at 12:29 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Mon, Dec 28, 2020 at 11:22:32AM -0500, Willem de Bruijn wrote:
> > > From: Willem de Bruijn <willemb@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@google.com>
> > > 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
> >
> >
> > So it looks like VIRTIO_NET_F_RX_TSTAMP should depend on both
> > VIRTIO_NET_F_RX_TSTAMP and VIRTIO_NET_F_HASH_REPORT then?
>
> Do you mean VIRTIO_NET_F_TX_TSTAMP depends on VIRTIO_NET_F_RX_TSTAMP?
>
> I think if either is enabled we need to enable the extended layout.
> Regardless of whether TX_HASH or HASH_REPORT are enabled. If they are
> not, then those fields are ignored.
I mean do we waste the 8 bytes for hash if TSTAMP is set but HASH is not?
If TSTAMP depends on HASH then point is moot.
> > I am not sure what does v12 mean here.
> >
> > virtio_net_hdr_v1 is just with VIRTIO_F_VERSION_1,
> > virtio_net_hdr_v1_hash is with VIRTIO_F_VERSION_1 and
> > VIRTIO_NET_F_HASH_REPORT.
> >
> > So this one is virtio_net_hdr_hash_tstamp I guess?
>
> Sounds better, yes, will change that.
>
> This was an attempt at identifying the layout with the likely next
> generation of the spec, 1.2. Similar to virtio_net_hdr_v1. But that is
> both premature and not very helpful.
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next prev parent reply other threads:[~2020-12-28 21:33 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-28 16:22 [PATCH rfc 0/3] virtio-net: add tx-hash, rx-tstamp and tx-tstamp Willem de Bruijn
2020-12-28 16:22 ` [PATCH rfc 1/3] virtio-net: support transmit hash report Willem de Bruijn
2020-12-28 16:28 ` Michael S. Tsirkin
2020-12-28 16:47 ` Willem de Bruijn
2020-12-28 17:22 ` Michael S. Tsirkin
2020-12-29 1:19 ` Willem de Bruijn
2020-12-28 21:36 ` Michael S. Tsirkin
2020-12-29 1:23 ` Willem de Bruijn
2020-12-28 16:22 ` [PATCH rfc 2/3] virtio-net: support receive timestamp Willem de Bruijn
2020-12-28 17:28 ` Michael S. Tsirkin
2020-12-28 19:30 ` Willem de Bruijn
2020-12-28 21:32 ` Michael S. Tsirkin [this message]
2020-12-29 1:05 ` Willem de Bruijn
2020-12-29 9:17 ` Jason Wang
2020-12-29 14:20 ` Willem de Bruijn
2020-12-30 8:38 ` Jason Wang
[not found] ` <20201228145953.08673c8c@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
2020-12-29 0:57 ` Willem de Bruijn
2020-12-30 8:44 ` Jason Wang
2021-02-02 13:05 ` kernel test robot
2021-02-02 14:08 ` Michael S. Tsirkin
2021-02-02 22:17 ` Willem de Bruijn
2021-02-02 23:02 ` Michael S. Tsirkin
2021-02-02 23:43 ` Willem de Bruijn
2020-12-28 16:22 ` [PATCH rfc 3/3] virtio-net: support transmit timestamp Willem de Bruijn
[not found] ` <20201230123854.GB2034@hoboy.vegasvil.org>
2020-12-30 15:25 ` Willem de Bruijn
2021-02-02 13:47 ` kernel test robot
2020-12-28 17:29 ` [PATCH rfc 0/3] virtio-net: add tx-hash, rx-tstamp and tx-tstamp Michael S. Tsirkin
2020-12-28 19:51 ` Willem de Bruijn
2020-12-28 21:38 ` Michael S. Tsirkin
2020-12-29 1:14 ` Willem de Bruijn
2021-01-06 20:32 ` Willem de Bruijn
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