Re: [Qemu-devel] [PATCH 10/18] vhost-user: add slave-fd support

[Eric Blake <eblake@redhat.com>]

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On 04/01/2016 05:16 AM, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> Learn to give a socket to the slave to let him make requests to the
> master.
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  docs/specs/vhost-user.txt | 23 ++++++++++++++++
>  hw/virtio/vhost-user.c    | 69 +++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 92 insertions(+)
> 
> diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> index 0312d40..8a635fa 100644
> --- a/docs/specs/vhost-user.txt
> +++ b/docs/specs/vhost-user.txt
> @@ -248,12 +248,25 @@ Once the source has finished migration, rings will be stopped by
>  the source. No further update must be done before rings are
>  restarted.
>  
> +Slave communication
> +-------------------
> +
> +An optional communication channel is provided if the slave
> +declares VHOST_USER_PROTOCOL_F_SLAVE_CHANNEL feature, to allow

s/declares/declares the/

> +the slave to make requests to the master.
> +
> +The fd is provided via VHOST_USER_SET_SLAVE_FD ancillary data.
> +
> +A slave may then send VHOST_USER_SLAVE_* messages to the master
> +using this fd communication channel.
> +
>  Protocol features
>  -----------------
>  
>  #define VHOST_USER_PROTOCOL_F_MQ             0
>  #define VHOST_USER_PROTOCOL_F_LOG_SHMFD      1
>  #define VHOST_USER_PROTOCOL_F_RARP           2
> +#define VHOST_USER_PROTOCOL_F_SLAVE_CHANNEL  3
>  
>  Message types
>  -------------
> @@ -464,3 +477,13 @@ Message types
>        is present in VHOST_USER_GET_PROTOCOL_FEATURES.
>        The first 6 bytes of the payload contain the mac address of the guest to
>        allow the vhost user backend to construct and broadcast the fake RARP.
> +
> + * VHOST_USER_SET_SLAVE_FD
> +      Id: 20
> +      Equivalent ioctl: N/A
> +      Master payload: N/A
> +
> +      Set the file descriptor for the salve to make VHOST_USER_SLAVE_*

s/salve/slave/

> +      request to the master. It is passed in the ancillary data.
> +      This message is only sent if VHOST_USER_PROTOCOL_F_SLAVE_CHANNEL
> +      feature is available.
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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