Re: RE: Help needed on gfx-passthrough

[Weidong Han <weidong.han@intel.com>]

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.

>> 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.
> 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.

Regards,
Weidong
> Thanks.
> Dietmar.
>   
>> Regards,
>> Weidong
>>
>>
>> -----Original Message-----
>> From: Dietmar Hahn [mailto:dietmar.hahn@ts.fujitsu.com] 
>> Sent: Thursday, March 18, 2010 5:29 PM
>> To: xen-devel@lists.xensource.com
>> 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.
>>
>>
>>