Re: [PATCH] vhost-user: add support for VHOST_USER_SET_STATUS

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

On Thu, May 14, 2020 at 09:33:32AM +0200, Maxime Coquelin wrote:
> It is usefull for the Vhost-user backend to know
> about about the Virtio device status updates,
> especially when the driver sets the DRIVER_OK bit.
> 
> With that information, no more need to do hazardous
> assumptions on when the driver is done with the
> device configuration.
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
> 
> This patch applies on top of Cindy's "vDPA support in qemu"
> series, which introduces the .vhost_set_state vhost-backend
> ops.
> 
>  docs/interop/vhost-user.rst | 12 ++++++++++++
>  hw/net/vhost_net.c          | 10 +++++-----
>  hw/virtio/vhost-user.c      | 35 +++++++++++++++++++++++++++++++++++
>  3 files changed, 52 insertions(+), 5 deletions(-)
> 
> diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst
> index 3b1b6602c7..f108de7458 100644
> --- a/docs/interop/vhost-user.rst
> +++ b/docs/interop/vhost-user.rst
> @@ -815,6 +815,7 @@ Protocol features
>    #define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD       12
>    #define VHOST_USER_PROTOCOL_F_RESET_DEVICE         13
>    #define VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS 14
> +  #define VHOST_USER_PROTOCOL_F_STATUS               15
>  
>  Master message types
>  --------------------
> @@ -1263,6 +1264,17 @@ Master message types
>  
>    The state.num field is currently reserved and must be set to 0.
>  
> +``VHOST_USER_SET_STATUS``
> +  :id: 36
> +  :equivalent ioctl: VHOST_VDPA_SET_STATUS
> +  :slave payload: N/A
> +  :master payload: ``u64``
> +
> +  When the ``VHOST_USER_PROTOCOL_F_STATUS`` protocol feature has been
> +  successfully negotiated, this message is submitted by the master to
> +  notify the backend with updated device status as defined in the Virtio
> +  specification.
> +
>  Slave message types
>  -------------------
>  
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index 463e333531..37f3156dbc 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -517,10 +517,10 @@ int vhost_set_state(NetClientState *nc, int state)
>  {
>      struct vhost_net *net = get_vhost_net(nc);
>      struct vhost_dev *hdev = &net->dev;
> -    if (nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) {
> -        if (hdev->vhost_ops->vhost_set_state) {
> -                return hdev->vhost_ops->vhost_set_state(hdev, state);
> -             }
> -        }
> +
> +    if (hdev->vhost_ops->vhost_set_state) {
> +        return hdev->vhost_ops->vhost_set_state(hdev, state);
> +    }
> +
>      return 0;
>  }
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index ec21e8fbe8..b7e52d97fc 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -59,6 +59,7 @@ enum VhostUserProtocolFeature {
>      VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
>      VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
>      VHOST_USER_PROTOCOL_F_RESET_DEVICE = 13,
> +    VHOST_USER_PROTOCOL_F_STATUS = 15,
>      VHOST_USER_PROTOCOL_F_MAX
>  };
>  
> @@ -100,6 +101,7 @@ typedef enum VhostUserRequest {
>      VHOST_USER_SET_INFLIGHT_FD = 32,
>      VHOST_USER_GPU_SET_SOCKET = 33,
>      VHOST_USER_RESET_DEVICE = 34,
> +    VHOST_USER_SET_STATUS = 36,
>      VHOST_USER_MAX
>  } VhostUserRequest;
>  
> @@ -1886,6 +1888,38 @@ static int vhost_user_set_inflight_fd(struct vhost_dev *dev,
>      return 0;
>  }
>  
> +static int vhost_user_set_state(struct vhost_dev *dev, int state)
> +{
> +    bool reply_supported = virtio_has_feature(dev->protocol_features,
> +                                              VHOST_USER_PROTOCOL_F_REPLY_ACK);
> +
> +    VhostUserMsg msg = {
> +        .hdr.request = VHOST_USER_SET_STATUS,
> +        .hdr.flags = VHOST_USER_VERSION,
> +        .hdr.size = sizeof(msg.payload.u64),
> +        .payload.u64 = (uint64_t)state,
> +    };
> +
> +    if (!virtio_has_feature(dev->protocol_features,
> +                VHOST_USER_PROTOCOL_F_STATUS)) {
> +        return -1;
> +    }
> +
> +    if (reply_supported) {
> +        msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
> +    }
> +
> +    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> +        return -1;
> +    }
> +
> +    if (reply_supported) {
> +        return process_message_reply(dev, &msg);
> +    }

So since we are doing this anyway, let's give backend the
opportunity to validate features and fail FEATURES_OK?



> +
> +    return 0;
> +}
> +
>  bool vhost_user_init(VhostUserState *user, CharBackend *chr, Error **errp)
>  {
>      if (user->chr) {
> @@ -1947,4 +1981,5 @@ const VhostOps user_ops = {
>          .vhost_backend_mem_section_filter = vhost_user_mem_section_filter,
>          .vhost_get_inflight_fd = vhost_user_get_inflight_fd,
>          .vhost_set_inflight_fd = vhost_user_set_inflight_fd,
> +        .vhost_set_state = vhost_user_set_state,
>  };
> -- 
> 2.25.4