Re: [Qemu-devel] [PATCH v10 6/7] vhost-user: add multiple queue support

[Michael S. Tsirkin]

On Fri, Sep 18, 2015 at 10:58:43PM +0800, Yuanhan Liu wrote:
> From: Changchun Ouyang <address@hidden>
> 
> This patch is initially based a patch from Nikolay Nikolaev.
> 
> This patch adds vhost-user multiple queue support, by creating a nc
> and vhost_net pair for each queue.
> 
> Qemu exits if find that the backend can't support number of requested
> queues (by providing queues=# option). The max number is queried by a
> new message, VHOST_USER_GET_QUEUE_NUM, and is sent only when protocol
> feature VHOST_USER_PROTOCOL_F_MQ is present first.
> 
> The max queue check is done at vhost-user initiation stage. We initiate
> one queue first, which, in the meantime, also gets the max_queues the
> backend supports.
> 
> In older version, it was reported that some messages are sent more times
> than necessary. Here we came an agreement with Michael that we could
> categorize vhost user messages to 2 types: non-vring specific messages,
> which should be sent only once, and vring specific messages, which should
> be sent per queue.
> 
> Here I introduced a helper function vhost_user_one_time_request(), which
> lists following messages as non-vring specific messages:
> 
>         VHOST_USER_SET_OWNER
>         VHOST_USER_RESET_DEVICE
>         VHOST_USER_SET_MEM_TABLE
>         VHOST_USER_GET_QUEUE_NUM
> 
> For above messages, we simply ignore them when they are not sent the first
> time.
> 
> Signed-off-by: Nikolay Nikolaev <address@hidden>
> Signed-off-by: Changchun Ouyang <address@hidden>
> Signed-off-by: Yuanhan Liu <address@hidden>

Eric, could you review schema changes please?

> ---
> v10: don't treat VHOST_USER_SET/GET_[PROTOCOL]_FEATURES as one time
>      request, as the two feature bits need to be stored at per-device.
> 
> v9: per suggested by Jason Wang, we could invoke qemu_chr_add_handlers()
>     once only, and invoke qemu_find_net_clients_except() at the handler
>     to gather all related ncs, for initiating all queues. Which addresses
>     a hidden bug in older verion in a more QEMU-like way.
> 
> v8: set net->dev.vq_index correctly inside vhost_net_init() based on the
>     value from net->nc->queue_index.
> ---
>  docs/specs/vhost-user.txt |  15 +++++
>  hw/net/vhost_net.c        |  10 ++--
>  hw/virtio/vhost-user.c    |  22 +++++++
>  hw/virtio/vhost.c         |   5 +-
>  net/vhost-user.c          | 146 
> +++++++++++++++++++++++++++++++++-------------
>  qapi-schema.json          |   6 +-
>  qemu-options.hx           |   5 +-
>  7 files changed, 159 insertions(+), 50 deletions(-)
> 
> diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> index 43db9b4..cfc9d41 100644
> --- a/docs/specs/vhost-user.txt
> +++ b/docs/specs/vhost-user.txt
> @@ -135,6 +135,21 @@ As older slaves don't support negotiating protocol 
> features,
>  a feature bit was dedicated for this purpose:
>  #define VHOST_USER_F_PROTOCOL_FEATURES 30
>  
> +Multiple queue support
> +----------------------
> +
> +Multiple queue is treated as a protocol extension, hence the slave has to
> +implement protocol features first. The multiple queues feature is supported
> +only when the protocol feature VHOST_USER_PROTOCOL_F_MQ (bit 0) is set:
> +#define VHOST_USER_PROTOCOL_F_MQ    0
> +
> +The max number of queues the slave supports can be queried with message
> +VHOST_USER_GET_PROTOCOL_FEATURES. Master should stop when the number of
> +requested queues is bigger than that.
> +
> +As all queues share one connection, the master uses a unique index for each
> +queue in the sent message to identify a specified queue.
> +
>  Message types
>  -------------
>  
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index bc88006..786191a 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -148,8 +148,11 @@ struct vhost_net *vhost_net_init(VhostNetOptions 
> *options)
>          fprintf(stderr, "vhost-net requires net backend to be setup\n");
>          goto fail;
>      }
> +    net->nc = options->net_backend;
>  
>      net->dev.max_queues = 1;
> +    net->dev.nvqs = 2;
> +    net->dev.vqs = net->vqs;
>  
>      if (backend_kernel) {
>          r = vhost_net_get_fd(options->net_backend);
> @@ -164,11 +167,10 @@ struct vhost_net *vhost_net_init(VhostNetOptions 
> *options)
>          net->dev.backend_features = 0;
>          net->dev.protocol_features = 0;
>          net->backend = -1;
> -    }
> -    net->nc = options->net_backend;
>  
> -    net->dev.nvqs = 2;
> -    net->dev.vqs = net->vqs;
> +        /* vhost-user needs vq_index to initiate a specific queue pair */
> +        net->dev.vq_index = net->nc->queue_index * net->dev.nvqs;
> +    }
>  
>      r = vhost_dev_init(&net->dev, options->opaque,
>                         options->backend_type);
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 5018fd6..e42fde6 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -187,6 +187,19 @@ static int vhost_user_write(struct vhost_dev *dev, 
> VhostUserMsg *msg,
>              0 : -1;
>  }
>  
> +static bool vhost_user_one_time_request(VhostUserRequest request)
> +{
> +    switch (request) {
> +    case VHOST_USER_SET_OWNER:
> +    case VHOST_USER_RESET_DEVICE:
> +    case VHOST_USER_SET_MEM_TABLE:
> +    case VHOST_USER_GET_QUEUE_NUM:
> +        return true;
> +    default:
> +        return false;
> +    }
> +}
> +
>  static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
>          void *arg)
>  {
> @@ -207,6 +220,15 @@ static int vhost_user_call(struct vhost_dev *dev, 
> unsigned long int request,
>          msg_request = request;
>      }
>  
> +    /*
> +     * For non-vring specific requests, like VHOST_USER_SET_MEM_TABLE,
> +     * we just need send it once in the first time. For later such
> +     * request, we just ignore it.
> +     */
> +    if (vhost_user_one_time_request(msg_request) && dev->vq_index != 0) {
> +        return 0;
> +    }
> +
>      msg.request = msg_request;
>      msg.flags = VHOST_USER_VERSION;
>      msg.size = 0;
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 7a7812d..c0ed5b2 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -874,8 +874,9 @@ static void vhost_eventfd_del(MemoryListener *listener,
>  static int vhost_virtqueue_init(struct vhost_dev *dev,
>                                  struct vhost_virtqueue *vq, int n)
>  {
> +    int vhost_vq_index = dev->vhost_ops->vhost_backend_get_vq_index(dev, n);
>      struct vhost_vring_file file = {
> -        .index = n,
> +        .index = vhost_vq_index,
>      };
>      int r = event_notifier_init(&vq->masked_notifier, 0);
>      if (r < 0) {
> @@ -926,7 +927,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
>      }
>  
>      for (i = 0; i < hdev->nvqs; ++i) {
> -        r = vhost_virtqueue_init(hdev, hdev->vqs + i, i);
> +        r = vhost_virtqueue_init(hdev, hdev->vqs + i, hdev->vq_index + i);
>          if (r < 0) {
>              goto fail_vq;
>          }
> diff --git a/net/vhost-user.c b/net/vhost-user.c
> index 93dcecd..4fa3d64 100644
> --- a/net/vhost-user.c
> +++ b/net/vhost-user.c
> @@ -39,37 +39,77 @@ static int vhost_user_running(VhostUserState *s)
>      return (s->vhost_net) ? 1 : 0;
>  }
>  
> -static int vhost_user_start(VhostUserState *s)
> +static void vhost_user_stop(int queues, NetClientState *ncs[])
>  {
> -    VhostNetOptions options;
> -
> -    if (vhost_user_running(s)) {
> -        return 0;
> -    }
> +    VhostUserState *s;
> +    int i;
>  
> -    options.backend_type = VHOST_BACKEND_TYPE_USER;
> -    options.net_backend = &s->nc;
> -    options.opaque = s->chr;
> +    for (i = 0; i < queues; i++) {
> +        assert (ncs[i]->info->type == NET_CLIENT_OPTIONS_KIND_VHOST_USER);
>  
> -    s->vhost_net = vhost_net_init(&options);
> +        s = DO_UPCAST(VhostUserState, nc, ncs[i]);
> +        if (!vhost_user_running(s)) {
> +            continue;
> +        }
>  
> -    return vhost_user_running(s) ? 0 : -1;
> +        if (s->vhost_net) {
> +            vhost_net_cleanup(s->vhost_net);
> +            s->vhost_net = NULL;
> +        }
> +    }
>  }
>  
> -static void vhost_user_stop(VhostUserState *s)
> +static int vhost_user_start(int queues, NetClientState *ncs[])
>  {
> -    if (vhost_user_running(s)) {
> -        vhost_net_cleanup(s->vhost_net);
> +    VhostNetOptions options;
> +    VhostUserState *s;
> +    int max_queues;
> +    int i;
> +
> +    options.backend_type = VHOST_BACKEND_TYPE_USER;
> +
> +    for (i = 0; i < queues; i++) {
> +        assert (ncs[i]->info->type == NET_CLIENT_OPTIONS_KIND_VHOST_USER);
> +
> +        s = DO_UPCAST(VhostUserState, nc, ncs[i]);
> +        if (vhost_user_running(s)) {
> +            continue;
> +        }
> +
> +        options.net_backend = ncs[i];
> +        options.opaque      = s->chr;
> +        s->vhost_net = vhost_net_init(&options);
> +        if (!s->vhost_net) {
> +            error_report("failed to init vhost_net for queue %d\n", i);
> +            goto err;
> +        }
> +
> +        if (i == 0) {
> +            max_queues = vhost_net_get_max_queues(s->vhost_net);
> +            if (queues > max_queues) {
> +                error_report("you are asking more queues than "
> +                             "supported: %d\n", max_queues);
> +                goto err;
> +            }
> +        }
>      }
>  
> -    s->vhost_net = 0;
> +    return 0;
> +
> +err:
> +    vhost_user_stop(i + 1, ncs);
> +    return -1;
>  }
>  
>  static void vhost_user_cleanup(NetClientState *nc)
>  {
>      VhostUserState *s = DO_UPCAST(VhostUserState, nc, nc);
>  
> -    vhost_user_stop(s);
> +    if (s->vhost_net) {
> +        vhost_net_cleanup(s->vhost_net);
> +        s->vhost_net = NULL;
> +    }
> +
>      qemu_purge_queued_packets(nc);
>  }
>  
> @@ -95,59 +135,81 @@ static NetClientInfo net_vhost_user_info = {
>          .has_ufo = vhost_user_has_ufo,
>  };
>  
> -static void net_vhost_link_down(VhostUserState *s, bool link_down)
> +static void net_vhost_link_down(int queues, NetClientState *ncs[],
> +                                bool link_down)
>  {
> -    s->nc.link_down = link_down;
> +    NetClientState *nc;
> +    int i;
>  
> -    if (s->nc.peer) {
> -        s->nc.peer->link_down = link_down;
> -    }
> +    for (i = 0; i < queues; i++) {
> +        nc = ncs[i];
>  
> -    if (s->nc.info->link_status_changed) {
> -        s->nc.info->link_status_changed(&s->nc);
> -    }
> +        nc->link_down = link_down;
> +
> +        if (nc->peer) {
> +            nc->peer->link_down = link_down;
> +        }
> +
> +        if (nc->info->link_status_changed) {
> +            nc->info->link_status_changed(nc);
> +        }
>  
> -    if (s->nc.peer && s->nc.peer->info->link_status_changed) {
> -        s->nc.peer->info->link_status_changed(s->nc.peer);
> +        if (nc->peer && nc->peer->info->link_status_changed) {
> +            nc->peer->info->link_status_changed(nc->peer);
> +        }
>      }
>  }
>  
>  static void net_vhost_user_event(void *opaque, int event)
>  {
> -    VhostUserState *s = opaque;
> +    const char *name = opaque;
> +    NetClientState *ncs[MAX_QUEUE_NUM];
> +    VhostUserState *s;
> +    int queues;
>  
> +    queues = qemu_find_net_clients_except(name, ncs,
> +                                          NET_CLIENT_OPTIONS_KIND_NIC,
> +                                          MAX_QUEUE_NUM);
> +    s = DO_UPCAST(VhostUserState, nc, ncs[0]);
>      switch (event) {
>      case CHR_EVENT_OPENED:
> -        vhost_user_start(s);
> -        net_vhost_link_down(s, false);
> +        if (vhost_user_start(queues, ncs) < 0) {
> +            exit(1);
> +        }
> +        net_vhost_link_down(queues, ncs, false);
>          error_report("chardev \"%s\" went up", s->chr->label);
>          break;
>      case CHR_EVENT_CLOSED:
> -        net_vhost_link_down(s, true);
> -        vhost_user_stop(s);
> +        net_vhost_link_down(queues, ncs, true);
> +        vhost_user_stop(queues, ncs);
>          error_report("chardev \"%s\" went down", s->chr->label);
>          break;
>      }
>  }
>  
>  static int net_vhost_user_init(NetClientState *peer, const char *device,
> -                               const char *name, CharDriverState *chr)
> +                               const char *name, CharDriverState *chr,
> +                               int queues)
>  {
>      NetClientState *nc;
>      VhostUserState *s;
> +    int i;
>  
> -    nc = qemu_new_net_client(&net_vhost_user_info, peer, device, name);
> +    for (i = 0; i < queues; i++) {
> +        nc = qemu_new_net_client(&net_vhost_user_info, peer, device, name);
>  
> -    snprintf(nc->info_str, sizeof(nc->info_str), "vhost-user to %s",
> -             chr->label);
> +        snprintf(nc->info_str, sizeof(nc->info_str), "vhost-user%d to %s",
> +                 i, chr->label);
>  
> -    s = DO_UPCAST(VhostUserState, nc, nc);
> +        /* We don't provide a receive callback */
> +        nc->receive_disabled = 1;
> +        nc->queue_index = i;
>  
> -    /* We don't provide a receive callback */
> -    s->nc.receive_disabled = 1;
> -    s->chr = chr;
> +        s = DO_UPCAST(VhostUserState, nc, nc);
> +        s->chr = chr;
> +    }
>  
> -    qemu_chr_add_handlers(s->chr, NULL, NULL, net_vhost_user_event, s);
> +    qemu_chr_add_handlers(chr, NULL, NULL, net_vhost_user_event, 
> (void*)name);
>  
>      return 0;
>  }
> @@ -226,6 +288,7 @@ static int net_vhost_check_net(void *opaque, QemuOpts 
> *opts, Error **errp)
>  int net_init_vhost_user(const NetClientOptions *opts, const char *name,
>                          NetClientState *peer, Error **errp)
>  {
> +    int queues;
>      const NetdevVhostUserOptions *vhost_user_opts;
>      CharDriverState *chr;
>  
> @@ -243,6 +306,7 @@ int net_init_vhost_user(const NetClientOptions *opts, 
> const char *name,
>          return -1;
>      }
>  
> +    queues = vhost_user_opts->has_queues ? vhost_user_opts->queues : 1;
>  
> -    return net_vhost_user_init(peer, "vhost_user", name, chr);
> +    return net_vhost_user_init(peer, "vhost_user", name, chr, queues);
>  }
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 2bada60..a372f49 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -2480,12 +2480,16 @@
>  #
>  # @vhostforce: #optional vhost on for non-MSIX virtio guests (default: 
> false).
>  #
> +# @queues: #optional number of queues to be created for multiqueue vhost-user
> +#          (default: 1) (Since 2.5)
> +#
>  # Since 2.1
>  ##
>  { 'struct': 'NetdevVhostUserOptions',
>    'data': {
>      'chardev':        'str',
> -    '*vhostforce':    'bool' } }
> +    '*vhostforce':    'bool',
> +    '*queues':        'int' } }
>  
>  ##
>  # @NetClientOptions
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 7e147b8..328404c 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -1990,13 +1990,14 @@ The hubport netdev lets you connect a NIC to a QEMU 
> "vlan" instead of a single
>  netdev.  @code{-net} and @code{-device} with parameter @option{vlan} create 
> the
>  required hub automatically.
>  
> address@hidden -netdev vhost-user,address@hidden,vhostforce=on|off]
> address@hidden -netdev vhost-user,address@hidden,vhostforce=on|off][,queues=n]
>  
>  Establish a vhost-user netdev, backed by a chardev @var{id}. The chardev 
> should
>  be a unix domain socket backed one. The vhost-user uses a specifically 
> defined
>  protocol to pass vhost ioctl replacement messages to an application on the 
> other
>  end of the socket. On non-MSIX guests, the feature can be forced with
> address@hidden
> address@hidden Use 'address@hidden' to specify the number of queues to
> +be created for multiqueue vhost-user.
>  
>  Example:
>  @example
> -- 
> 1.9.0