From: "Charles (Chas) Williams" <ciwillia@brocade.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: <dev@dpdk.org>, <mtetsuyah@gmail.com>
Subject: Re: [dpdk-dev] [PATCH 2/2] vhost: start vhost servers once
Date: Fri, 30 Dec 2016 16:26:27 -0500 [thread overview]
Message-ID: <be570b9e-8fe4-7b45-2598-9a44cd0fedf2@brocade.com> (raw)
In-Reply-To: <20161230031501.GE21789@yliu-dev.sh.intel.com>
On 12/29/2016 10:15 PM, Yuanhan Liu wrote:
> On Thu, Dec 29, 2016 at 10:58:11AM -0500, Charles (Chas) Williams wrote:
>> On 12/29/2016 03:52 AM, Yuanhan Liu wrote:
>>> On Wed, Dec 28, 2016 at 04:10:52PM -0500, Charles (Chas) Williams wrote:
>>>> Start a vhost server once during devinit instead of during device start
>>>> and stop. Some vhost clients, QEMU, don't re-attaching to sockets when
>>>> the vhost server is stopped and later started. Preserve existing behavior
>>>> for vhost clients.
>>>
>>> I didn't quite get the idea what you are going to fix.
>>
>> The issue I am trying to fix is QEMU interaction when DPDK's vhost is
>> acting as a server to QEMU vhost clients. If you create a vhost server
>> device, it doesn't create the actual datagram socket until you call
>> .dev_start(). If you call .dev_stop() is also deletes those sockets.
>> For QEMU, this is a problem since QEMU doesn't know how to re-attach to
>> datagram sockets that have gone away.
>
> Thanks! And I'd appreciate it if you could have written the commit log
> this way firstly.
>
>> .dev_start()/.dev_stop() seems to roughly means link up and link down
>> so I understand why you might want to add/remove the datagram sockets.
>> However, in practice, this doesn't seem to make much sense for a DPDK
>> vhost server.
>
> Agree.
>
>> This doesn't seem like the right way to indicate link
>> status to vhost clients.
>>
>> It seems like it would just be easier to do this for both clients and
>> servers, but I don't know why it was done this way originally so I
>> choose to keep the client behavior.
>
> I don't think there are any differences between DPDK acting as client or
> server. To me, the right logic seems to be (for both DPDK as server and
> client).
>
> For register,
> - register the vhost socket at probe stage (either at rte_pmd_vhost_probe
> or at eth_dev_vhost_create).
> - start the vhost session right after the register when we haven't started
> it before.
>
> For unregister,
> - invoke rte_vhost_driver_unregister() at rte_pmd_vhost_remove().
OK. This will be much easier than what I submitted.
> For dev_start/stop,
> - set allow_queuing to 1/0 for start/stop, respectively.
Unfortunately, I don't think this will work. new_device() doesn't happen
until a client connects. allow_queueing seems to be following the status
of the "wire" as it where. .dev_start()/.dev_stop() is the link of local
port connected to the wire (administratively up or down as it where).
.dev_start() can happen before new_device() and attempting to RX for a
client that doesn't exist doesn't seem like a good idea. Perhaps another
flag that follows dev_started, but for the queues?
next prev parent reply other threads:[~2016-12-30 21:26 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-28 21:10 [dpdk-dev] [PATCH 1/2] vhost: reference count fix for nb_started_ports Charles (Chas) Williams
2016-12-28 21:10 ` [dpdk-dev] [PATCH 2/2] vhost: start vhost servers once Charles (Chas) Williams
2016-12-29 8:52 ` Yuanhan Liu
2016-12-29 15:58 ` Charles (Chas) Williams
2016-12-30 3:15 ` Yuanhan Liu
2016-12-30 21:26 ` Charles (Chas) Williams [this message]
2017-01-03 8:16 ` Yuanhan Liu
2016-12-29 8:51 ` [dpdk-dev] [PATCH 1/2] vhost: reference count fix for nb_started_ports Yuanhan Liu
2016-12-29 15:49 ` Charles (Chas) Williams
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