netdev - Re: [RFC] Discuss about an new idea "Vsock over Virtio-net"

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Date:   Fri, 30 Nov 2018 20:45:39 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     jiangyiwen <jiangyiwen@...wei.com>, stefanha@...hat.com,
        stefanha@...il.com, netdev@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [RFC] Discuss about an new idea "Vsock over Virtio-net"


On 2018/11/29 下午10:00, Michael S. Tsirkin wrote:
> On Thu, Nov 15, 2018 at 04:24:38PM +0800, Jason Wang wrote:
>> On 2018/11/15 下午3:04, Michael S. Tsirkin wrote:
>>> On Thu, Nov 15, 2018 at 11:56:03AM +0800, jiangyiwen wrote:
>>>> Hi Stefan, Michael, Jason and everyone,
>>>>
>>>> Several days ago, I discussed with jason about "Vsock over Virtio-net".
>>>> This idea has two advantages:
>>>> First, it can use many great features of virtio-net, like batching,
>>>> mergeable rx buffer and multiqueue, etc.
>>>> Second, it can reduce many duplicate codes and make it easy to be
>>>> maintained.
>>> I'm not sure I get the motivation. Which features of
>>> virtio net are relevant to vsock?
>>
>> Vsock is just a L2 (and above) protocol from the view of the device.
> I don't believe so. I think virtio-vsock operates at a transport level.
> There is in theory a bit of network level but we don't really implement
> it as it's only host to guest.  I am not aware of any data link
> functionality n virtio-vsock. virtio-vsock provides services such as
> connection-oriented communication, reliability, flow control and
> multiplexing.


Ok, consider it doesn't implement L2, it's pretty fit for virtio-net I 
believe?


>
>> So I
>> think we should answer the question why we need two different paths for
>> networking traffic? Or what is the fundamental reason that makes vsock does
>> not go for virtio-net?
> So virtio-vsock ensures reliability.


It's done at the level of protocol instead of virtio transport or virtio 
device.


>   If you want to compare it with
> something that would be TCP or QUIC.  The fundamental difference between
> virtio-vsock and e.g. TCP is that TCP operates in a packet loss environment.
> So they are using timers for reliability, and receiver is always free to
> discard any unacked data.


Virtio-net knows nothing above L2, so they are totally transparent to 
device itself. I still don't get why not using virtio-net instead.


Thanks


>
>
>> I agree they could be different type of devices but codes could be shared in
>> both guest and host (or even qemu) for not duplicating features(bugs).
>>
>> Thanks
>>
>>
>>> The ones that you mention
>>> all seem to be mostly of use to the networking stack.
>>>
>>>