linux-kernel - Re: [RFC] vhost_mdev: add network control vq support

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Date:   Thu, 31 Oct 2019 09:44:11 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Tiwei Bie <tiwei.bie@...el.com>
Cc:     mst@...hat.com, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        dan.daly@...el.com, cunming.liang@...el.com,
        zhihong.wang@...el.com, lingshan.zhu@...el.com
Subject: Re: [RFC] vhost_mdev: add network control vq support


On 2019/10/30 下午7:54, Tiwei Bie wrote:
> On Wed, Oct 30, 2019 at 03:04:37PM +0800, Jason Wang wrote:
>> On 2019/10/30 下午2:17, Tiwei Bie wrote:
>>> On Tue, Oct 29, 2019 at 06:51:32PM +0800, Jason Wang wrote:
>>>> On 2019/10/29 下午6:17, Tiwei Bie wrote:
>>>>> This patch adds the network control vq support in vhost-mdev.
>>>>> A vhost-mdev specific op is introduced to allow parent drivers
>>>>> to handle the network control commands come from userspace.
>>>> Probably work for userspace driver but not kernel driver.
>>> Exactly. This is only for userspace.
>>>
>>> I got your point now. In virtio-mdev kernel driver case,
>>> the ctrl-vq can be special as well.
>>>
>> Then maybe it's better to introduce vhost-mdev-net on top?
>>
>> Looking at the other type of virtio device:
>>
>> - console have two control virtqueues when multiqueue port is enabled
>>
>> - SCSI has controlq + eventq
>>
>> - GPU has controlq
>>
>> - Crypto device has one controlq
>>
>> - Socket has eventq
>>
>> ...
> Thanks for the list! It looks dirty to define specific
> commands and types in vhost UAPI for each of them in the
> future. It's definitely much better to find an approach
> to solve it once for all if possible..
>
> Just a quick thought, considering all vhost-mdev does
> is just to forward settings between parent and userspace,
> I'm wondering whether it's possible to make the argp
> opaque in vhost-mdev UAPI and just introduce one generic
> ioctl command to deliver these device specific commands
> (which are opaque in vhost-mdev as vhost-mdev just pass
> the pointer -- argp) defined by spec.


It looks that using opaque pointer is probably not good for UAPI. And we 
need also invent API for eventq.


>
> I'm also fine with exposing ctrlq to userspace directly.
> PS. It's interesting that some devices have more than
> one ctrlq. I need to take a close look first..


Thanks.


>
>
>> Thanks
>>