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Re: [Xen-devel] Xen 4.0.0 first release candidate / graphics passthru

On Thu, Jan 21, 2010 at 05:52:15PM +0800, Weidong Han wrote:
> Jean Guyader wrote:
>> 2010/1/21 Pasi Kärkkäinen <pasik@xxxxxx>:
>>> On Thu, Jan 21, 2010 at 09:09:35AM +0000, Jean Guyader wrote:
>>>> 2010/1/21 Pasi Kärkkäinen <pasik@xxxxxx>:
>>>>> On Tue, Jan 12, 2010 at 10:05:12AM +0000, Keir Fraser wrote:
>>>>>> On 12/01/2010 09:32, "Pasi Kärkkäinen" <pasik@xxxxxx> wrote:
>>>>>>>>> Does 4.0 include gpu passthru features? If not are there any updated
>>>>>>>>> patches to try gpu passthru with 4.x?
>>>>>>>> There is support (c/s 20144).
>>>>>>> Btw is it possible now to specify a file to load the VGA bios from?
>>>>>>> earlier it was required to hardcode it into some header file or so.
>>>>>> I think it is hardcoded that qemu will take a copy of the host system's 
>>>>>> BIOS
>>>>>> (i.e., for the primary host VGA). Other options would be easy to 
>>>>>> implement
>>>>>> I'm sure, if someone's interested.
>>>>> I was just looking at same older mails, and it seems for example Teo En 
>>>>> Ming
>>>>> and others who got Xen VGA passthrough working had to copy the 
>>>>> vgabios-pt.bin
>>>>> to tools/firmware/vgabios/ before building Xen.
>>>>> That's not very practical..
>>>> Right now the code copy the bios from 0xC0000. So if you want to pass 
>>>> through
>>>> a secondary display adapter with the vga bios you are not copying the 
>>>> right one,
>>>> that why this hack was for.
>>>> Surely the code could be modified to add an option to copy the bios of
>>>> the right card.
>>> Ok, thanks for the info.
>>> Do I remember correctly that there was a problem with copying the BIOS from 
>>> some cards,
>>> or on some setups? And that's why the patch to load it from a file was made?
>> Yes, I think that was because of that, and I'm not sure about the
>> intel IGD but I think that was causing some issue.
>> The code could have a cleanup and use sysfs to get the rombios, if I
>> works with the intel graphic card I think we should do that.
>> Jean
> vbios copied from 0xC0000 doesn't work for some graphics cards, e.g.  
> Nvidia GS 8400, due to the vbios code is modified after initialization.  
> So it needs to load it from file. yes, it's not practical, Intel IGD  
> cards don't have this issue in our tests.  One possible good solution is  
> to load vbios from expansion ROM of graphics cards, but we found  
> expansion ROM address are invalid for some graphics cards, even using  
> Linux upstream.  It needs to look into Linux code.

So at this point should be add two things:

1) option in guest cfgfile telling from which card to copy the vbios from
2) option to load the vbios from a file specified in guest cfgfile

How does that sound like? 

-- Pasi

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