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

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Jan 21, 2010 at 06:24:29PM +0800, Weidong Han wrote:
> Pasi Kärkkäinen wrote:
>> 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
>>   
> I think adding an option in guest config file to indicate primary or  
> secondary gfx assignment can cover this.

Ok.

>> 2) option to load the vbios from a file specified in guest cfgfile
>>   
> I don't prefer this. It involves much manual work for users. It's better  
> to find a general solution which is also easy to use.
>

Can we find a general solution in time for Xen 4.0 release? 

If not, then a solution requiring manual work is better than compiling 
from a source on every machine..

Mr. Teo En Ming: Did you try the latest xen-unstable (4.0-rcX) to see 
if it works for you? 

-- Pasi


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