Re: [Qemu-devel] Re: virtio-serial: An interface for host-guest communication

[Anthony Liguori <anthony@codemonkey.ws>]

Jamie Lokier wrote:
> With multiple X servers, there can be more than one currently logged in user.
>
> Same with multiple text consoles - that's more familiar.
>
> Which one owns /dev/vmch3?
>   

For a VMM, copy/paste should work with whatever user has the active X 
session that's controlling the physical display.

Yes, it could get complicated if we supported multiple video cards, but 
fortunately we don't :-)

I really think you need to have a copy/paste daemon that allows multiple 
X sessions to connect to it and then that daemon can somehow determine 
who is the "active" session.

This is part of the reason I've been pushing for a concrete example.  
All the signs here point to a privileged daemon that delegates to 
multiple users.  I think just about any use-case will have a similar model.

It really suggests that you need _one_ vmchannel that's exposed to 
userspace with a single userspace daemon that consumes it.  You want the 
flexibility of a userspace daemon in determining how you multiplex and 
do security.  I don't think it's something you want to bake into the 
userspace/kernel interface.

And if you have a single daemon that serves vmchannel sessions, that 
daemon can make it transparent whether the session is going over 
/dev/ttyS0, a network device, /dev/hvc1, etc.

Regards,

Anthony Liguori