Re: [PATCH v3 1/3] eal: add channel for multi-process communication

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> 
> Previouly, there are three channels for multi-process
> (i.e., primary/secondary) communication.
>   1. Config-file based channel, in which, the primary process writes
>      info into a pre-defined config file, and the secondary process
>      reads the info out.
>   2. vfio submodule has its own channel based on unix socket for the
>      secondary process to get container fd and group fd from the
>      primary process.
>   3. pdump submodule also has its own channel based on unix socket for
>      packet dump.
> 
> It'd be good to have a generic communication channel for multi-process
> communication to accomodate the requirements including:
>   a. Secondary wants to send info to primary, for example, secondary
>      would like to send request (about some specific vdev to primary).
>   b. Sending info at any time, instead of just initialization time.
>   c. Share FDs with the other side, for vdev like vhost, related FDs
>      (memory region, kick) should be shared.
>   d. A send message request needs the other side to response immediately.
> 
> This patch proposes to create a communication channel, based on datagram
> unix socket, for above requirements. Each process will block on a unix
> socket waiting for messages from the peers.
> 
> Three new APIs are added:
> 
>   1. rte_eal_mp_action_register() is used to register an action,
>      indexed by a string, when a component at receiver side would like
>      to response the messages from the peer processe.
>   2. rte_eal_mp_action_unregister() is used to unregister the action
>      if the calling component does not want to response the messages.
>   3. rte_eal_mp_sendmsg() is used to send a message, and returns
>      immediately. If there are n secondary processes, the primary
>      process will send n messages.
> 
> Suggested-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
> ---

Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>