Re: Xen VGA graphics passthrough for secondary adapters, vBAR=pBAR etc

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

Pasi Kärkkäinen wrote:
> Hello,
>
> Now that Xen 4.0.0 is out and has support for primary graphics passthru
> and many people have been using it already and asking for a status update
> for secondary adapter passthru I thought of opening a new thread about this.
>
> What are the actual issues that need to be resolved to get the 
> secondary graphics passthru working? Probably related to VGA BIOS execution
> in the guest? 
>   
I think of two things need to be solved for secondary gfx assigned:
 1) claim VGA cycle for it to display in VGA for guest, VGA is owned by 
primary gfx.
 2) load VGA bios from file, because you cannot get it from memory like 
primary gfx.
> How about the vBAR=pBAR stuff required for some (Nvidia) cards? 
> How do we get that functionality integrated so people don't need additional patches? 
>   
vBAR=pBAR patch is a bit tricky. It needs to cook a new clean vBAR=pBAR 
patch if integrate it in upstream.
> Was there also a problem that a working VGA BIOS cannot be copied from some cards 
> and they need to use/load it from a file? 
>   
Load it from a file should work for all cards, but it's not user 
friendly  (involving manual steps). It's better to implement a generic 
approach to get VGA bios for various gfx cards including primary and 
secondary gfx. The direct way is to load it from expansion rom, but it 
doesn't always work because expansion rom address may be invalid (the 
bridge may doesn't have enough memory for gfx card).

Regards,
Weidong
> Thanks!
>
> -- Pasi
>
> btw. I've created a wiki page where we can list all the tested/working graphics adapters:
> http://wiki.xensource.com/xenwiki/XenVGAPassthroughTestedAdapters
>
>
>