Re: [Qemu-devel] [PATCH] virtio-net: consolidate guest announcement with qemu_announce_self

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Mar 29, 2017 at 04:19:50PM -0400, Vladislav Yasevich wrote:
> virtio announcements seem to run on its own timer with it's own
> repetition loop and are invoked separately from qemu_announce_self.
> This patch consolidates announcements into a single location and
> allows other nics to provide it's own

their own

> announcement capabilities, if
> necessary.
> 
> This is also usefull

or useful?

> in support of exposing qemu_announce_self through
> qmp/hmp.

I'm guessing this is the real reason for the change.
How is it helpful for that? Pls clarify in the commit log.

> Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
> ---
>  hw/net/virtio-net.c            | 30 ++++++++----------------------
>  include/hw/virtio/virtio-net.h |  2 --
>  include/net/net.h              |  2 ++
>  migration/savevm.c             |  6 ++++++
>  4 files changed, 16 insertions(+), 24 deletions(-)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index c321680..6e9ce4f 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -110,14 +110,16 @@ static bool virtio_net_started(VirtIONet *n, uint8_t status)
>          (n->status & VIRTIO_NET_S_LINK_UP) && vdev->vm_running;
>  }
>  
> -static void virtio_net_announce_timer(void *opaque)
> +static void virtio_net_announce(NetClientState *nc)
>  {
> -    VirtIONet *n = opaque;
> +    VirtIONet *n = qemu_get_nic_opaque(nc);
>      VirtIODevice *vdev = VIRTIO_DEVICE(n);
>  
> -    n->announce_counter--;
> -    n->status |= VIRTIO_NET_S_ANNOUNCE;
> -    virtio_notify_config(vdev);
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_NET_F_GUEST_ANNOUNCE) &&
> +        virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) {
> +            n->status |= VIRTIO_NET_S_ANNOUNCE;
> +            virtio_notify_config(vdev);
> +    }
>  }
>  
>  static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
> @@ -427,8 +429,6 @@ static void virtio_net_reset(VirtIODevice *vdev)
>      n->nobcast = 0;
>      /* multiqueue is disabled by default */
>      n->curr_queues = 1;
> -    timer_del(n->announce_timer);
> -    n->announce_counter = 0;
>      n->status &= ~VIRTIO_NET_S_ANNOUNCE;
>  
>      /* Flush any MAC and VLAN filter table state */
> @@ -868,11 +868,6 @@ static int virtio_net_handle_announce(VirtIONet *n, uint8_t cmd,
>      if (cmd == VIRTIO_NET_CTRL_ANNOUNCE_ACK &&
>          n->status & VIRTIO_NET_S_ANNOUNCE) {
>          n->status &= ~VIRTIO_NET_S_ANNOUNCE;
> -        if (n->announce_counter) {
> -            timer_mod(n->announce_timer,
> -                      qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) +
> -                      self_announce_delay(n->announce_counter));
> -        }
>          return VIRTIO_NET_OK;
>      } else {
>          return VIRTIO_NET_ERR;

you will notice that this runs at VM speeds with QEMU_CLOCK_VIRTUAL,
while the self announce you are tying this to runs with
QEMU_CLOCK_REALTIME.

So this switch seems wrong to me: by the time VM is started
on destination all timers might have expired.


> @@ -1609,12 +1604,6 @@ static int virtio_net_post_load_device(void *opaque, int version_id)
>          qemu_get_subqueue(n->nic, i)->link_down = link_down;
>      }
>  
> -    if (virtio_vdev_has_feature(vdev, VIRTIO_NET_F_GUEST_ANNOUNCE) &&
> -        virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) {
> -        n->announce_counter = SELF_ANNOUNCE_ROUNDS;
> -        timer_mod(n->announce_timer, qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL));
> -    }
> -
>      return 0;
>  }
>  
> @@ -1829,6 +1818,7 @@ static NetClientInfo net_virtio_info = {
>      .receive = virtio_net_receive,
>      .link_status_changed = virtio_net_set_link_status,
>      .query_rx_filter = virtio_net_query_rxfilter,
> +    .announce = virtio_net_announce,
>  };
>  
>  static bool virtio_net_guest_notifier_pending(VirtIODevice *vdev, int idx)
> @@ -1934,8 +1924,6 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
>      qemu_macaddr_default_if_unset(&n->nic_conf.macaddr);
>      memcpy(&n->mac[0], &n->nic_conf.macaddr, sizeof(n->mac));
>      n->status = VIRTIO_NET_S_LINK_UP;
> -    n->announce_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
> -                                     virtio_net_announce_timer, n);
>  
>      if (n->netclient_type) {
>          /*
> @@ -1997,8 +1985,6 @@ static void virtio_net_device_unrealize(DeviceState *dev, Error **errp)
>          virtio_net_del_queue(n, i);
>      }
>  
> -    timer_del(n->announce_timer);
> -    timer_free(n->announce_timer);
>      g_free(n->vqs);
>      qemu_del_nic(n->nic);
>      virtio_cleanup(vdev);
> diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
> index 1eec9a2..0c597f4 100644
> --- a/include/hw/virtio/virtio-net.h
> +++ b/include/hw/virtio/virtio-net.h
> @@ -94,8 +94,6 @@ typedef struct VirtIONet {
>      char *netclient_name;
>      char *netclient_type;
>      uint64_t curr_guest_offloads;
> -    QEMUTimer *announce_timer;
> -    int announce_counter;
>      bool needs_vnet_hdr_swap;
>  } VirtIONet;
>  
> diff --git a/include/net/net.h b/include/net/net.h
> index 99b28d5..598f523 100644
> --- a/include/net/net.h
> +++ b/include/net/net.h
> @@ -64,6 +64,7 @@ typedef int (SetVnetLE)(NetClientState *, bool);
>  typedef int (SetVnetBE)(NetClientState *, bool);
>  typedef struct SocketReadState SocketReadState;
>  typedef void (SocketReadStateFinalize)(SocketReadState *rs);
> +typedef void (NetAnnounce)(NetClientState *);
>  
>  typedef struct NetClientInfo {
>      NetClientDriver type;
> @@ -84,6 +85,7 @@ typedef struct NetClientInfo {
>      SetVnetHdrLen *set_vnet_hdr_len;
>      SetVnetLE *set_vnet_le;
>      SetVnetBE *set_vnet_be;
> +    NetAnnounce *announce;
>  } NetClientInfo;
>  
>  struct NetClientState {
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 3b19a4a..5c1d8dc 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -113,9 +113,15 @@ static void qemu_announce_self_iter(NICState *nic, void *opaque)
>      int len;
>  
>      trace_qemu_announce_self_iter(qemu_ether_ntoa(&nic->conf->macaddr));
> +
>      len = announce_self_create(buf, nic->conf->macaddr.a);
>  
>      qemu_send_packet_raw(qemu_get_queue(nic), buf, len);
> +
> +    /* if the NIC provides it's own announcement support, use it as well */
> +    if (nic->ncs->info->announce) {
> +        nic->ncs->info->announce(nic->ncs);
> +    }
>  }


Can we switch existing qemu announcements to QEMU_CLOCK_VIRTUAL?

It's an interesting question, and I'm not sure.

I note that this seems to interact interestingly with recent dgilbert's
patch sweaking announcement timing. Some coordination might be
helpful here.


>  
> -- 
> 2.7.4