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

[Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>]

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?

> 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.
My problem is that I don't see any access to extended config registers.
Therefore my question for help in debugging to see what the vgabios is doing.
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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