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Date:   Thu, 12 May 2022 09:41:44 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Alvaro Karsz <alvaro.karsz@...id-run.com>
Cc:     netdev@...r.kernel.org, Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rabeeh Khoury <rabeeh@...id-run.com>
Subject: Re: [PATCH] net: virtio_net: support interrupt coalescing

On Thu, May 12, 2022 at 03:54:28PM +0300, Alvaro Karsz wrote:
>     So first, please at least reserve the feature in the virtio spec.
>     Preferably add the specification as well.
>     Here's one way to do it:
>     https://github.com/oasis-tcs/virtio-spec#use-of-github-issues
> 
> 
> Sorry about that.
> I sent a patch to the virtio comment list, but thought that I should wait
> until I got a few comments before opening a github issue.
> https://lists.oasis-open.org/archives/virtio-comment/202205/msg00016.html
> Should I open the github issue now? or should I wait a little for more comments
> on the virtio-spec patch?

At this point you can wait.

> 
>     You want all these to be LE. Native endian's unpredictable in lots of
>     virt settings.
> 
> 
> I will fix this, wait a few more days to see if there are more comments, and
> then create a new version of the patch.
> 
> Thanks
> 
> On Thu, May 12, 2022 at 12:55 PM Michael S. Tsirkin <mst@...hat.com> wrote:
> 
>     On Thu, May 12, 2022 at 11:35:23AM +0300, Alvaro Karsz wrote:
>     > Control a Virtio network device interrupt coalescing parameters
>     > using the control virtqueue.
>     >
>     > New VirtIO network feature: VIRTIO_NET_F_INTR_COAL.
>     >
>     > A device that supports this fetature can receive
>     > VIRTIO_NET_CTRL_INTR_COAL control commands.
>     >
>     > * VIRTIO_NET_CTRL_INTR_COAL_USECS_SET:
>     >       change the rx-usecs and tx-usecs parameters.
>     >
>     >       rx-usecs - Time to delay an RX interrupt after packet arrival in
>     >               microseconds.
>     >
>     >       tx-usecs - Time to delay a TX interrupt after a sending a packet
>     >               in microseconds.
>     >
>     > * VIRTIO_NET_CTRL_INTR_COAL_FRAMES_SET:
>     >       change the rx-max-frames and tx-max-frames parameters.
>     >
>     >       rx-max-frames: Number of packets to delay an RX interrupt after
>     >               packet arrival.
>     >
>     >       tx-max-frames: Number of packets to delay a TX interrupt after
>     >               sending a packet.
>     >
>     > Signed-off-by: Alvaro Karsz <alvaro.karsz@...id-run.com>
> 
>     So first, please at least reserve the feature in the virtio spec.
>     Preferably add the specification as well.
>     Here's one way to do it:
>     https://github.com/oasis-tcs/virtio-spec#use-of-github-issues
> 
> 
>     > ---
>     >  drivers/net/virtio_net.c        | 108 ++++++++++++++++++++++++++++----
>     >  include/uapi/linux/virtio_net.h |  34 +++++++++-
>     >  2 files changed, 128 insertions(+), 14 deletions(-)
>     >
>     > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>     > index cbba9d2e8f3..4806c35ddd5 100644
>     > --- a/drivers/net/virtio_net.c
>     > +++ b/drivers/net/virtio_net.c
>     > @@ -261,6 +261,12 @@ struct virtnet_info {
>     >       u8 duplex;
>     >       u32 speed;
>     >
>     > +     /* Interrupt coalescing settings */
>     > +     u32 tx_usecs;
>     > +     u32 rx_usecs;
>     > +     u32 tx_frames_max;
>     > +     u32 rx_frames_max;
>     > +
>     >       unsigned long guest_offloads;
>     >       unsigned long guest_offloads_capable;
>     >
>     > @@ -2594,19 +2600,75 @@ static int virtnet_set_coalesce(struct net_device
>     *dev,
>     >  {
>     >       struct virtnet_info *vi = netdev_priv(dev);
>     >       int i, napi_weight;
>     > +     struct scatterlist sgs_usecs, sgs_frames;
>     > +     struct virtio_net_ctrl_coal_frames c_frames;
>     > +     struct virtio_net_ctrl_coal_usec c_usecs;
>     > +     bool update_napi,
>     > +     intr_coal = virtio_has_feature(vi->vdev, VIRTIO_NET_F_INTR_COAL);
>     > +
>     > +     /* rx_coalesce_usecs/tx_coalesce_usecs are supported only
>     > +      * if VIRTIO_NET_F_INTR_COAL feature is set.
>     > +      */
>     > +     if (!intr_coal && (ec->rx_coalesce_usecs || ec->tx_coalesce_usecs))
>     > +             return -EOPNOTSUPP;
>     > +
>     > +     if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_INTR_COAL)) {
>     > +             /* Send usec command */
>     > +             c_usecs.tx_usecs = ec->tx_coalesce_usecs;
>     > +             c_usecs.rx_usecs = ec->rx_coalesce_usecs;
>     > +             sg_init_one(&sgs_usecs, &c_usecs, sizeof(c_usecs));
>     > +
>     > +             if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_INTR_COAL,
>     > +                                     
>      VIRTIO_NET_CTRL_INTR_COAL_USECS_SET,
>     > +                                       &sgs_usecs))
>     > +                     return -EINVAL;
>     > +
>     > +             /* Save parameters */
>     > +             vi->tx_usecs = ec->tx_coalesce_usecs;
>     > +             vi->rx_usecs = ec->rx_coalesce_usecs;
>     > +
>     > +             /* Send frames command */
>     > +             c_frames.tx_frames_max = ec->tx_max_coalesced_frames;
>     > +             c_frames.rx_frames_max = ec->rx_max_coalesced_frames;
>     > +             sg_init_one(&sgs_frames, &c_frames, sizeof(c_frames));
>     > +
>     > +             if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_INTR_COAL,
>     > +                                     
>      VIRTIO_NET_CTRL_INTR_COAL_FRAMES_SET,
>     > +                                       &sgs_frames))
>     > +                     return -EINVAL;
>     > +
>     > +             /* Save parameters */
>     > +             vi->tx_frames_max = ec->tx_max_coalesced_frames;
>     > +             vi->rx_frames_max = ec->rx_max_coalesced_frames;
> 
> 
> 
> 
>     > +     }
>     > +
>     > +     /* Should we update NAPI? */
>     > +     update_napi = ec->tx_max_coalesced_frames <= 1 &&
>     > +                     ec->rx_max_coalesced_frames == 1;
>     >
>     > -     if (ec->tx_max_coalesced_frames > 1 ||
>     > -         ec->rx_max_coalesced_frames != 1)
>     > +     /* If interrupt coalesing feature is not set, and we can't update
>     NAPI, return an error */
>     > +     if (!intr_coal && !update_napi)
>     >               return -EINVAL;
>     >
>     > -     napi_weight = ec->tx_max_coalesced_frames ? NAPI_POLL_WEIGHT : 0;
>     > -     if (napi_weight ^ vi->sq[0].napi.weight) {
>     > -             if (dev->flags & IFF_UP)
>     > -                     return -EBUSY;
>     > -             for (i = 0; i < vi->max_queue_pairs; i++)
>     > -                     vi->sq[i].napi.weight = napi_weight;
>     > +     if (update_napi) {
>     > +             napi_weight = ec->tx_max_coalesced_frames ?
>     NAPI_POLL_WEIGHT : 0;
>     > +             if (napi_weight ^ vi->sq[0].napi.weight) {
>     > +                     if (dev->flags & IFF_UP) {
>     > +                             /* If Interrupt coalescing feature is not
>     set, return an error.
>     > +                              * Otherwise exit without changing the NAPI
>     paremeters
>     > +                              */
>     > +                             if (!intr_coal)
>     > +                                     return -EBUSY;
>     > +
>     > +                             goto exit;
>     > +                     }
>     > +
>     > +                     for (i = 0; i < vi->max_queue_pairs; i++)
>     > +                             vi->sq[i].napi.weight = napi_weight;
>     > +             }
>     >       }
>     >
>     > +exit:
>     >       return 0;
>     >  }
>     >
>     > @@ -2616,14 +2678,25 @@ static int virtnet_get_coalesce(struct net_device
>     *dev,
>     >                               struct netlink_ext_ack *extack)
>     >  {
>     >       struct ethtool_coalesce ec_default = {
>     > -             .cmd = ETHTOOL_GCOALESCE,
>     > -             .rx_max_coalesced_frames = 1,
>     > +             .cmd = ETHTOOL_GCOALESCE
>     >       };
>     > +
>     >       struct virtnet_info *vi = netdev_priv(dev);
>     > +     bool intr_coal = virtio_has_feature(vi->vdev,
>     VIRTIO_NET_F_INTR_COAL);
>     > +
>     > +     /* Add Interrupt coalescing settings */
>     > +     if (intr_coal) {
>     > +             ec_default.rx_coalesce_usecs = vi->rx_usecs;
>     > +             ec_default.tx_coalesce_usecs = vi->tx_usecs;
>     > +             ec_default.tx_max_coalesced_frames = vi->tx_frames_max;
>     > +             ec_default.rx_max_coalesced_frames = vi->rx_frames_max;
>     > +     } else {
>     > +             ec_default.rx_max_coalesced_frames = 1;
>     > +     }
>     >
>     >       memcpy(ec, &ec_default, sizeof(ec_default));
>     >
>     > -     if (vi->sq[0].napi.weight)
>     > +     if (!intr_coal && vi->sq[0].napi.weight)
>     >               ec->tx_max_coalesced_frames = 1;
>     >
>     >       return 0;
>     > @@ -2743,7 +2816,7 @@ static int virtnet_set_rxnfc(struct net_device
>     *dev, struct ethtool_rxnfc *info)
>     >  }
>     >
>     >  static const struct ethtool_ops virtnet_ethtool_ops = {
>     > -     .supported_coalesce_params = ETHTOOL_COALESCE_MAX_FRAMES,
>     > +     .supported_coalesce_params = ETHTOOL_COALESCE_MAX_FRAMES |
>     ETHTOOL_COALESCE_USECS,
>     >       .get_drvinfo = virtnet_get_drvinfo,
>     >       .get_link = ethtool_op_get_link,
>     >       .get_ringparam = virtnet_get_ringparam,
>     > @@ -3423,6 +3496,8 @@ static bool virtnet_validate_features(struct
>     virtio_device *vdev)
>     >            VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_RSS,
>     >                            "VIRTIO_NET_F_CTRL_VQ") ||
>     >            VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_HASH_REPORT,
>     > +                          "VIRTIO_NET_F_CTRL_VQ") ||
>     > +          VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_INTR_COAL,
>     >                            "VIRTIO_NET_F_CTRL_VQ"))) {
>     >               return false;
>     >       }
>     > @@ -3558,6 +3633,13 @@ static int virtnet_probe(struct virtio_device
>     *vdev)
>     >       if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
>     >               vi->mergeable_rx_bufs = true;
>     >
>     > +     if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_INTR_COAL)) {
>     > +             vi->rx_usecs = 0;
>     > +             vi->tx_usecs = 0;
>     > +             vi->tx_frames_max = 0;
>     > +             vi->rx_frames_max = 0;
>     > +     }
>     > +
>     >       if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT))
>     >               vi->has_rss_hash_report = true;
>     >
>     > @@ -3786,7 +3868,7 @@ 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_RSS, VIRTIO_NET_F_HASH_REPORT
>     > +     VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT, VIRTIO_NET_F_INTR_COAL
>     >
>     >  static unsigned int features[] = {
>     >       VIRTNET_FEATURES,
>     > diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/
>     virtio_net.h
>     > index 3f55a4215f1..b65a4295270 100644
>     > --- a/include/uapi/linux/virtio_net.h
>     > +++ b/include/uapi/linux/virtio_net.h
>     > @@ -56,7 +56,7 @@
>     >  #define VIRTIO_NET_F_MQ      22      /* Device supports Receive Flow
>     >                                        * Steering */
>     >  #define VIRTIO_NET_F_CTRL_MAC_ADDR 23        /* Set MAC address */
>     > -
>     > +#define VIRTIO_NET_F_INTR_COAL       55      /* Guest can handle
>     Interrupt coalescing */
>     >  #define VIRTIO_NET_F_HASH_REPORT  57 /* Supports hash report */
>     >  #define VIRTIO_NET_F_RSS       60    /* Supports RSS RX steering */
>     >  #define VIRTIO_NET_F_RSC_EXT   61    /* extended coalescing info */
>     > @@ -355,4 +355,36 @@ struct virtio_net_hash_config {
>     >  #define VIRTIO_NET_CTRL_GUEST_OFFLOADS   5
>     >  #define VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET        0
>     >
>     > +/*
>     > + * Control interrupt coalescing.
>     > + *
>     > + * Request the device to change the interrupt coalescing parameters.
>     > + *
>     > + * Available with the VIRTIO_NET_F_INTR_COAL feature bit.
>     > + */
>     > +#define VIRTIO_NET_CTRL_INTR_COAL            6
>     > +/*
>     > + * Set the rx-usecs/tx-usecs patameters.
>     > + * rx-usecs - Number of microseconds to delay an RX interrupt after
>     packet arrival.
>     > + * tx-usecs - Number of microseconds to delay a TX interrupt after a
>     sending a packet.
>     > + */
>     > +struct virtio_net_ctrl_coal_usec {
>     > +     __u32 tx_usecs;
>     > +     __u32 rx_usecs;
>     > +};
>     > +
>     > +#define VIRTIO_NET_CTRL_INTR_COAL_USECS_SET          0
>     > +
>     > +/*
>     > + * Set the rx-max-frames/tx-max-frames patameters.
>     > + * rx-max-frames - Number of packets to delay an RX interrupt after
>     packet arrival.
>     > + * tx-max-frames - Number of packets to delay a TX interrupt after
>     sending a packet.
>     > + */
>     > +struct virtio_net_ctrl_coal_frames {
>     > +     __u32 tx_frames_max;
>     > +     __u32 rx_frames_max;
>     > +};
>     > +
> 
>     You want all these to be LE. Native endian's unpredictable in lots of
>     virt settings.
> 
> 
>     > +#define VIRTIO_NET_CTRL_INTR_COAL_FRAMES_SET         1
>     > +
>     >  #endif /* _UAPI_LINUX_VIRTIO_NET_H */
>     > --
>     > 2.32.0
> 
> 
> 
> 
> --
> [uc]
> 
> Alvaro Karsz, Software
> +972-50-7696862| https://www.solid-run.com

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