Re: [Qemu-devel] [virtio-comment] Re: [RFC 1/2] spec/vhost-user: Introduce secondary channel for slave initiated requests

[Wei Wang <wei.w.wang@intel.com>]

On 04/25/2017 07:55 PM, Maxime Coquelin wrote:
> Hi Wei,
>
> On 04/24/2017 10:05 AM, Wei Wang wrote:
>> On 04/14/2017 05:03 PM, Marc-André Lureau wrote:
>>> Hi
>>>
>>> On Tue, Apr 11, 2017 at 5:53 PM Maxime Coquelin 
>>> <maxime.coquelin@redhat.com <mailto:maxime.coquelin@redhat.com>> wrote:
>>>
>>>     Hi Marc-André,
>>>
>>>     On 04/11/2017 03:06 PM, Marc-André Lureau wrote:
>>>     > Hi
>>>     >
>>>     > On Tue, Apr 11, 2017 at 12:10 PM Maxime Coquelin
>>>     > <maxime.coquelin@redhat.com <mailto:maxime.coquelin@redhat.com>
>>>     <mailto:maxime.coquelin@redhat.com
>>>     <mailto:maxime.coquelin@redhat.com>>> wrote:
>>>     >
>>>     >     This vhost-user specification update aims at enabling the
>>>     >     slave to send requests to the master using a dedicated socket
>>>     >     created by the master.
>>>     >
>>>     >     It can be used for example when the slave implements a device
>>>     >     IOTLB to send cache miss requests to the master.
>>>     >
>>>     >     The message types list is updated with an "Initiator" 
>>> field to
>>>     >     indicate for each type whether the master and/or slave can
>>>     >     initiate the request.
>>>     >
>>>     >     Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com
>>>     <mailto:maxime.coquelin@redhat.com>
>>>     >     <mailto:maxime.coquelin@redhat.com
>>>     <mailto:maxime.coquelin@redhat.com>>>
>>>     >
>>>     >
>>>     > This is very similar to a patch I proposed for shutdown slave
>>>     initiated
>>>     > requests:
>>>     > 
>>> https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg00095.html
>>>
>>>     Indeed, thanks for pointing this out, I wasn't aware of your 
>>> series.
>>>
>>>     I find your proposal of having dedicated messages types
>>>     (VHOST_USER_SLAVE_*) cleaner.
>>>
>>> ok
>>>
>>>     Are you ok if I handover your patch, and replace
>>>     VHOST_USER_SET_SLAVE_FD to VHOST_USER_SET_SLAVE_REQ_FD?
>>>
>>>
>>> They are very similar, I suggest you update your patch with the best 
>>> of both.
>>>
>>> I suppose you came to the same conclusion with me that trying to 
>>> make the communication both ways on the same fd would be quite 
>>> difficult, although it's a bit strange that the qemu implementation 
>>> forces the design of the protocol in some direction.
>>> -- 
>>>
>>
>> When would you get the implementation patch ready? Thanks.
>
> I sent second version of the RFC on April 14th, which comprises the
> implementation:
> https://lists.gnu.org/archive/html/qemu-devel/2017-04/msg02467.html

Thanks, Maxime. I was trying to make the connection bidirectional
(https://lists.gnu.org/archive/html/qemu-devel/2016-12/msg02617.html),
which was reported as problematic due to the possibility of race (though
I think it can be solved by re-sending the msg in that rare case).

Anyway, hope to see you guys' second channel based implementation to
be merged soon. I would also consider to switch to use it then.

Best,
Wei