Re: [Xen-users] How does VNC in Xen worked?

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> Thanks for your explanation.
> I'm wondering whether there're any articles or papers discussing the
> implementation of VNC server in Xen system. I surfed XenWiki but did not
> find much.

There's not a large amount of documentation on how this works; the most likely 
place to find information is probably by searching the mailing list archives 
(I hear the archives on http://xen.markmail.org have a good search facility).

> I would wish to do a little development myself if more information
> avaliable since I'm familiar with vnc infrastructure.

On the most recent versions of Xen, VNC support for both HVM and PV guests is 
provided by the Qemu's inbuilt VNC server.

Xen's Qemu-based "device model" process is responsible (for HVM guests) for 
emulating a real graphics card then exporting its display over the network.  
For PV guests, a special PV-aware version of the device-model is used to 
connect to the guest's virtual framebuffer and export that using VNC.

Older versions of Xen used libvncserver in various places but that dependency 
was eventually eliminated.

Does that help?

Cheers,
Mark

> Thank you again for your kindly help.
>
> Warm Regards,
> Lucky
>
> "Ross S. W. Walker" <rwalker@xxxxxxxxxxxxx> wrote: Lucky wrote:
> > Hi everyone,
> > I'm wondering the mechanism of VNC server in Xen. If anyone has
> > some reference article please kindly indicate.
> >
> > I'm wondering whether VNC in Xen need one to install VNC server
> > in the guest domain. I'm still trying to connect to my guest domain
> > (RHEL4) from a remote VNC client but had not succeed yet.
> >
> > While doing this, I'm wondering how VNC service in Xen worked. Does it:
> >
> > 1- Just running a vnc server in the guest domain and we could
> > configure to access the guest domain through a network bridge
> > in Xen. In this case, the VNC service indeed has nothing to
> > do with Xen system, and it's only an application in guest
> > domain which could get through Xen's supervisor to the network.
> >
> > Or:
> >
> > 2- VNC server was a part built in IOEMU module of Xen, and
> > directly grub the keyboard, mouse, and screen IO from the
> > supervisor. In this case, the guest domain OS is not aware
> > about whether the VNC service is running, and it just
> > receives normal input/output IO from Xen system.
>
> It's #2.
>
> > The above are two possible way that I could imaging, but if
> > VNC is running by other miracle methods, please kindly
> > explain or indicate references.
>
> Take a look at /etc/xend-config.sxp for allowing guest vnc
> to listen on all interfaces by default (normally it's just the
> loopback).
>
> Or if you wish to configure it per-guest (more secure) you
> will need the vnclisten option set to '0.0.0.0' in the guests'
> config files to have them listen on all interfaces.
>
> -Ross
>
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