Re: [Qemu-devel] Re: A new direction for vmchannel?

[Dor Laor]

Anthony Liguori wrote:
> Gleb Natapov wrote:
> > On Fri, Jan 23, 2009 at 08:45:33AM -0600, Anthony Liguori wrote:
> >  
> > > Thoughts?
> > >
> > >     
> > Looks good, but I am not to much familiar with p9. Will it provide us
> > with stream semantics?
>
> Sure.  It has read and write operations.  You just have to implement 
> them in the same sort of way you'd implement them for a character device.

So why not having a virtio pv-serial device.
Above this device/driver users can have several implementations/semantics:
   - raw messages
   - 9p
   - userspace tcp/ip
      - We already used the host part of it.
      - It provides reliability and handles migration too.
      - Since its userspace, there is no routing/addressing involved.
The above will make windows and other OSs happy and users can still get 
9p or tcp or raw.
Maybe even the virtio console can be based over it (Don't really know 
nothing about it )

btw: I do suggest to keep the former work of nic based vmchannel. Except 
for the cmdline,
every thing else is committed. It might be good for older OSs and just 
work out of the box.


> >  How much work is needed to support this in
> > Windows (what is your estimation)?
>
> If you structure your guest applications to use a library, sort of 
> like libsysfs, then on Windows, you could implement a 9P client in 
> userspace.  I have a 9P client that can be used for this.  You just 
> need some way to get the stream to userspace.  You could write a 
> virtio windows driver that exposed the stream down to userspace.  You 
> could also use an alternative transport for Windows (like a serial port).
>
> >  Will migration be transparent to
> > in guest users?
> >   
>
> There's no better migration story for vmchannel backends implemented 
> outside of QEMU.  For the ones in QEMU, migration should be transparent.
>
> Regards,
>
> Anthony Liguori
>
> > --
> >             Gleb.
> >