RE: [Xen-devel] X11_EnterFullScreen fails

["Jayant Mangalampalli" <Jayant_Mangalampalli@xxxxxxxxxxx>]

We are currently using AMD Sahara board (with on board ATI graphics
chip) and could never get the full screen to work. We tried using MSI
video card (that plugs into AGP slot) and could not get full screen to
work there too. However, when we switched to Diamond's Stealth 3D 2000
Pro video card (that plugs into PCI slot), we could get the full screen
to work. Moreover, to rule out "real mode switch" possibility, we built
and ran a user level application that leverages X11 drivers through SDL
to map a BMP image on full screen. The results are exactly the same on
target as they are with xen's guest domain - full screen does not work
with on boards graphics chip, does not work with MSI card in the AGP
slot, but works with Stealth in PCI slot.

Is anybody aware of issues with onboard ATI graphics chip that could
prevent guest virtual frame buffer not to span full-screen?

Thanks
Jayant

-----Original Message-----
From: Petersson, Mats [mailto:Mats.Petersson@xxxxxxx] 
Sent: Wednesday, May 30, 2007 10:01 PM
To: Jayant Mangalampalli; xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-devel] X11_EnterFullScreen fails

> -----Original Message-----
> From: Jayant Mangalampalli [mailto:Jayant_Mangalampalli@xxxxxxxxxxx] 
> Sent: 30 May 2007 17:23
> To: Petersson, Mats; xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-devel] X11_EnterFullScreen fails
> 
> If this is the case, though, why does only full-screen mode fail? Why
> not the normal non-full-screen mode?
> 
> -----Original Message-----
> From: Jayant Mangalampalli 
> Sent: Wednesday, May 30, 2007 9:51 PM
> To: 'Petersson, Mats'; xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-devel] X11_EnterFullScreen fails
> 
> Highly likely. Unfortunately we cannot salvage any data during crash.
> But I think this is a great pointer, especially since I am also facing
> problems trying to get TinyX to start in the graphics mode - but the
> vesafb driver tries to access the BIOS and it fails for 
> exactly the same
> reason (it is in protected mode by that time). The result is, however,
> not a crash but a flimsy looking "text mode" like screen.


Well, I don't really know the answer. But I used to work on Windows
graphics drivers, and I know that sometimes switching the display mode
will incur a BIOS call (I never quite understood when this was and when
it wouldn't happen - I think it depends on several things, including the
driver-code itself which may support some modes and say "I don't care
about supporting this mode" - at which point the OS would call the
BIOS[1] code to attempt it that way). Non-full-screen mode doesn't
require BIOS calls, for the obvious reason that the graphics mode isn't
being changed then - full-screen mode may well switch from the current
display mode to a different display-mode even if it's the same
resolution, e.g. 16bits per pixel or 8 bits per pixel, just as an
example.

Also, is the SDL screen in text or graphical mode when you switch to
full-screen? If it's in text-mode, then it's 99% sure that the BIOS is
involved. 

I'm not saying this IS what happens, just that it's something to
investigate.

You may be able to capture more of the trace-back if you use serial
console either from Linux or the hypervisor, and if it's hypervisor that
crashes [and you don't use serial console] you may get more info by
"noreboot" on the "xen" line in your grub.conf (or similar). 

[1] BIOS = VGA-BIOS, not the "start my PC BIOS". 

--
Mats

> 
> Thanks
> Jayant  
> 
> -----Original Message-----
> From: Petersson, Mats [mailto:Mats.Petersson@xxxxxxx] 
> Sent: Wednesday, May 30, 2007 9:38 PM
> To: Jayant Mangalampalli; xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-devel] X11_EnterFullScreen fails
> 
>  
> 
> > -----Original Message-----
> > From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> > [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> > Jayant Mangalampalli
> > Sent: 30 May 2007 17:05
> > To: xen-devel@xxxxxxxxxxxxxxxxxxx
> > Subject: [Xen-devel] X11_EnterFullScreen fails
> > 
> > I am trying to set the guest window to full-screen mode but 
> > the domain consistently crashes when I try to do that. The 
> > problem could be traced to a point where X11-driver used by 
> > SDL itself fails. Here is the call trace before system 
> > crashes (most recent call last):
> > 
> > SDL_video.c::SDL_SetVideoMode() makes a call to 
> > video->SetVideoMode(). (We use X11 video driver)
> > 
> > video->SetVideoMode() = SDL_x11video.c::X11_SetVideoMode()
> > 
> > The above makes a call to SDL_x11video.c::X11_ResizeWindow() 
> > which makes a call to X11_EnterFullScreen() (in SDL_x11modes.c)
> > 
> > X11 does support full-screen mode and I am unable to 
> > understand why it is initiated by xen. Has anyone tried this?
> 
> What's the crash symptoms? Is it possible that the X11 driver 
> is calling
> the BIOS, and that this fails in Xen due to restrictions on running
> real-mode, which doesn't happen in native mode?
> 
> --
> Mats
> > 
> > Thanks,
> > 
> > Jayant Mangalampalli
> > 
> > 
> 
> 
> 
> 
> 



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