Linux Virtualization - Nov 2018 - [RFC] Discuss about an new idea "Vsock over Virtio-net"

On 2018/11/15 ??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. 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?

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.
>
>

On Thu, Nov 15, 2018 at 04:24:38PM +0800, Jason Wang
wrote:
> 
> On 2018/11/15 ??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.
> 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. 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.

> 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.
> > 
> >

On 2018/11/29 ??10:00, Michael S. Tsirkin wrote:
> On Thu, Nov 15, 2018 at 04:24:38PM +0800, Jason Wang wrote:
>> On 2018/11/15 ??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.
>>>
>>>