Re: [PATCH v2 07/12] eal: add channel for primary/secondary communication

From: "Tan, Jianfeng" <jianfeng.tan@intel.com>
To: "Burakov, Anatoly" <anatoly.burakov@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>
Cc: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
	"Richardson, Bruce" <bruce.richardson@intel.com>,
	"Pattan, Reshma" <reshma.pattan@intel.com>,
	"viktorin@rehivetech.com" <viktorin@rehivetech.com>
Subject: Re: [PATCH v2 07/12] eal: add channel for primary/secondary communication
Date: Fri, 29 Sep 2017 01:03:48 +0000	[thread overview]
Message-ID: <ED26CBA2FAD1BF48A8719AEF02201E36512FA4DC@SHSMSX103.ccr.corp.intel.com> (raw)
In-Reply-To: <cda99f5f-7355-8bcf-1291-798ef0028c89@intel.com>

+ Reshma and Jan.

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Burakov, Anatoly
> Sent: Thursday, September 28, 2017 11:30 PM
> To: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v2 07/12] eal: add channel for
> primary/secondary communication
> 
> On 28-Sep-17 4:01 PM, Ananyev, Konstantin wrote:
> > Hi Jianfeng,
> >
> >
> >> -----Original Message-----
> >> From: Tan, Jianfeng
> >> Sent: Thursday, September 28, 2017 2:56 PM
> >> To: dev@dpdk.org
> >> Cc: Richardson, Bruce <bruce.richardson@intel.com>; Ananyev,
> Konstantin <konstantin.ananyev@intel.com>; De Lara Guarch, Pablo
> >> <pablo.de.lara.guarch@intel.com>; thomas@monjalon.net;
> yliu@fridaylinux.org; maxime.coquelin@redhat.com; mtetsuyah@gmail.com;
> >> Yigit, Ferruh <ferruh.yigit@intel.com>; Tan, Jianfeng
> <jianfeng.tan@intel.com>
> >> Subject: [PATCH v2 07/12] eal: add channel for primary/secondary
> communication
> >>
> >> Previouly, there is only one way for primary/secondary to exchange
> >> messages, that is, primary process writes info into some predefind
> >> file, and secondary process reads info out. That cannot address
> >> the requirements:
> >>    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.
> >>
> >> This patch proposes to create a communication channel, as an unix
> >> socket connection, for above requirements. Primary will listen on
> >> the unix socket; secondary will connect this socket to talk.
> >>
> >> Three new APIs are added:
> >>
> >>    1. rte_eal_mp_action_register is used to register an action,
> >>       indexed by a string; if the calling component wants to
> >>       response the messages from the corresponding component in
> >>       its primary process or secondary processes.
> >>    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.
> >
> > I think we already have similar channel in librte_pdump().
> > Also it seems like eal_vfio also has it's own socket to communicate
> between mp/sp.
> > Could we probably make it generic - so same code (and socket) be used by
> all such  places.
> > Konstantin
> >
> 
> Agreed, however looking at this, it's already a generic-enough solution,
> and other places could be fixed to use this in later releases.

Yes, to provide a generic communication way, instead of one channel for each subsystem, is the goal of this patch.

Reshma and Jan, can I ask comment from you to have a look if the way of this patch is generic enough to cover pdump and vfio-sync's requirement?

Possible limitation of this patch (so far) is that it only provides an async way for request/response, do we need synchronous way?

> That said, i believe this particular part of the patchset should go in as a
> separate patchset and more design consideration and input from others.

OK, let's collect more info here, and then take out this patch out as a separate patch.

Thanks,
Jianfeng