Virtio Drivers on Dragonfly

Oliver Fromme check+la6ebi00rs8kogo6 at
Tue Oct 12 05:21:08 PDT 2010

Michael Neumann wrote:
 > Another great application of vkernels could be for laptops. Imagine your
 > laptop runs on DragonFly, and your host kernel is running a X11 display
 > server, while all your X11 clients run inside the vkernel. This enables
 > you to checkpoint the vkernel, shut down the laptop, and to later
 > restore where you left off (assuming X11 doesn't keep state on the
 > X11-server).

That won't work, because various client data is stored
inside the X server (resources, properties, bitmaps, ...).

Usually an X client will terminate immediately when its
connection to the X server is lost.  Also, the X server
will drop all data related to an X client when it loses
the connection to that client.

In order to make the scenario work that you describe, you
would also have to checkpoint the X server at the same
time (which would be difficult because of dependencies on
hardware and drivers), and freeze the connections between
X server and X clients somehow so they're not lost.

Alternatively you could run the X server within the same
vkernel, and find a way to pass graphics hardware access
to the vkernel (not trivial either, because you will have
to restore the graphics hardware state correctly upon thaw).
But I guess this would have serious performance problems.

A third way to do what you want would be to use Xvnc inside
the vkernel.  This would be easy to do, and might even be
fast enough.  The X clients connect to the Xvnc server
inside the vkernel, so no connections are lost upon check-
point.  Upon thaw, you simply re-connect to the Xvnc server
with your VNC client (e.g. tightvnc) running under the host
kernel's X server.  I think this should be feasible.

Best regards

Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M.
Handelsregister: Registergericht Muenchen, HRA 74606,  Geschäftsfuehrung:
secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün-
chen, HRB 125758,  Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart

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