RE: [Xen-users] Graphics Pass-Through Questions

["Nick Couchman" <Nick.Couchman@xxxxxxxxx>]

>>> On 2010/04/23 at 10:20, "Dustin Henning" <Dustin.Henning@xxxxxxxxxxx> 
>>> wrote: 
> Nick,
>       Regarding passing through USB controllers, I'd say the reason they
> don't work during boot is the same reason you can't boot to a virtual SCSI
> disk, the virtual BIOS doesn't support it.  I'm also guessing that making
> the virtual BIOS boot to virtual SCSI disks would be FAR easier than making
> it support real physical USB cards (because there are so many, and each may
> be unique, when USB first came out, it wasn't an option to use a USB
> keyboard until Windows booted because the BIOS wouldn't emulate the legacy
> device from the USB HID device, and I'm guessing this is still true of
> add-on USB cards vs BIOSes that do).  That said, you might be able to get by
> with buying a PCI-PS/2 card and passing it through with a PS/2 keyboard and
> mouse, but I don't know, it would be an experiment, and you might even be
> just as likely to end up with a PCI USB card that converts its PS/2 ports to
> HID, in which case it would still be a no-go (I'm assuming the native
> Windows drivers would support the PS/2 chip if you got the right card).

I'm guessing you're right - I just didn't know if there was some other way to 
get keyboard and mouse support working at boot time with VGA pass-through.  I 
find it hard to believe that other folks didn't his this same roadblock in the 
development and testing of the VGA pass-through technology, along with those 
out there using VGA pass-through.  The machines I'm testing have a fairly small 
number of available slots, and I'd rather not have to go purchase a PCI PS/2 
card for each machine that I run this way.  Maybe once the USB pass-through is 
a little easier to accomplish this can be done in a simpler fashion without the 
need to pass through the entire USB controller.  For now, I'll just deal with 
it and try to work around it as best I can.

>       Regarding graphics pass-through and VFB, I assume a driver might be
> written to support this, UltraVNC uses a driver to pick up what is on the
> video card quicker than VNC otherwise would, and there is no visible
> dual-monitor setup in Windows for that.  nVidia drivers have a setting to
> clone video to two monitors as well, but that is on the same video card, so
> perhaps simpler.  Regardless, someone would have to be willing to work on
> setting it up.  However, if you are just shooting for remote assistance,
> installing a VNC server on the domU would probably make more sense.

Yeah, I'd much rather do the VFB mirroring below the guest O/S level.  This 
would allow for debugging boot-time options, it would provide a work-around for 
the above problem, and it would make it easy to manage remotely via SSH to the 
dom0 machine.  However, I understand what you're saying, and I know that 
several of the VNC variants already have this feature when you install into the 
domU O/S.  My hope was that it's something that can be accomplished for Xen 
below that level, especially since the support already exists on Linux (Gnome 
uses this to provide VNC access to your running Gnome desktop remotely).

Thanks for the feedback!

-Nick



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