Re: [Xen-devel] RE: Help needed on gfx-passthrough

[Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>]

Am 19.03.2010 schrieb Weidong Han:
> Dietmar Hahn wrote:
> > Am 18.03.2010 schrieb Han, Weidong:
> >   
> >> There is a wiki page for xen gfx passthru: 
> >> http://wiki.xensource.com/xenwiki/XenVGAPassthrough. pls read it.
> >>     
> > Yes I did this.
> >   
> >> I didn't try your gfx card. As you know, some vbios of nVidia gfx cards 
> >> have vbios re-execution issue, which results in no display in VGA mode.
> >>     
> > Yes I read this on the mailing list, you mean FLR issues?
> >   
> Not exactly. Another possibility is that vbios bits may be truncated or 
> modified after initialization in host, thus it might result in 
> re-execution issue.
This would be very ugly.

> 
> >> You can have a try with loading vbios from file and make vBAR = pBAR. You 
> >> can find the corresponding patches in xen-devel mailing list.
> >>     
> >
> > I tried this already.
> > I want to look a little bit deeper to understand whats going on.
> > I saw your igd_passthru patch qemu hw/pci.c for special handling of some 
> > pci config registers of the host bridge and maybe I need a similar patch
> > for the special PCI Express Graphics Port bridge.
> >   
> Discrete gfx card is an independent pci device. I don't think it will 
> depend on platform. IGD is integrated in chipset, and there are some 
> dependencies on chipset.
This sounds reasonable.

> > My problem is that I don't see any access to extended config registers.
> >   
> PCIe extended config registers (>256bytes) are not virtualized in Xen qemu.
> 
> > Therefore my question for help in debugging to see what the vgabios is 
> > doing.
> >   
> I don't know how to see what vgabios is doing. If you can find the 
> vgabios engineer, maybe you can dump and send gfx register values to him 
> for analysis.
I don't know whether this is possible.
Thanks.
Dietmar.

> 
> Regards,
> Weidong
> > Thanks.
> > Dietmar.
> >   
> >> Regards,
> >> Weidong
> >>
> >>
> >> -----Original Message-----
> >> From: Dietmar Hahn [mailto:dietmar.hahn@xxxxxxxxxxxxxx] 
> >> Sent: Thursday, March 18, 2010 5:29 PM
> >> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> >> Cc: Han, Weidong
> >> Subject: Help needed on gfx-passthrough
> >>
> >> Hi list,
> >>
> >> I try to get gfx-passthrough on a laptop:
> >> Intel PM45 Express chipset with extern nvidia craphics card G96M [Quadro 
> >> FX 770M]
> >> I can't see the bios boot messages and also not the grub boot loader.
> >> The domU linux boot messages appear on the screen.
> >>
> >> For me it looks like the vgabios gets not started or works not well.
> >> In the domU I can read the vgabios from /dev/mem and it's the same as in 
> >> dom0.
> >> If I change the hvmloader to use the standard vgabios from firmware/vgabios
> >> I see the bios and grub boot messages.
> >>
> >> I added some tracing to qemu-dm (pt_*read/write and pci_*read/write) to see
> >> accesses to the emulated chipset and graphics card but I can see no 
> >> difference
> >> between using the original vgabios or the emulated vgabios within the 
> >> hvmloader.
> >>
> >> Now my question: how can I debug this problem. How can I see whether the 
> >> vgabios
> >> gets started and initialises the graphics card? 
> >> I'am not fit enough in this area and documentation is very rare!
> >> Thanks in advance!
> >>
> >> Dietmar.
> >>

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