Re: Experimental results for VGA passthrough

["Beng Heng, Ng" <bengheng@eecs.umich.edu>]

Perhaps I should clarify that the low resolution with Intel driver is
observed in Windows XP. It works fine in Vista. I was able to run 3DMark
on Vista.

- Beng Heng

Beng Heng, Ng wrote:
> I noticed that Xen does not boot if only the Intel IGD is present and
> selected, i.e. only one graphics device.
> 
> Also, I'm not able to get high resolution if I passthrough Intel IGD and
> install the Intel Graphics Media Accelerator driver. Ironically, I can
> get higher resolution and color if I remove the driver. Has anyone
> encountered similar observations before?
> 
> - Beng Heng
> 
> djmagee@mageenet.net wrote:
>> The DQ45CB does not have enough PCI Express lanes to drive the IGD and a
>> x16 graphics card at the same time.
>>  
>> -----Original Message-----
>> From: xen-devel-bounces@lists.xensource.com
>> [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of Beng Heng,
>> Ng
>> Sent: Thursday, June 04, 2009 11:09 AM
>> To: xen-devel
>> Subject: [Xen-devel] Experimental results for VGA passthrough
>>
>> Hi,
>>
>> I tried patching Xen 3.4 Testing c/s 19628 with vga passthrough code
>> (less HID passthrough), and did some tests. I made some modifications in
>> pci_setup to skip loading the emulated VGA bios and pci_load_option_roms
>> to load the passthrough VGA bios. My setup uses Intel DQ45CB and ATI
>> HD2600XT.
>>
>> The BDFs for the relevant devices are:
>> Intel IGD  00:02.0
>> ATI gfx    01:00.0, 01:00.1
>> There's 2 BDFs for ATI because one of them is for the Audio. Both have
>> to be passed through simultaneously.
>>
>> In the first scenario, Intel IGD is set up as the primary for Dom0. The
>> ATI gfx is passed through to DomU. Interestingly, it is the screen that
>> is connected to Intel's output that displays DomU (albeit with few
>> colors and low resolution). However, in the Device Manager, ATI is
>> reported. I believe this is because Intel's address space is being
>> mapped, instead of ATI's. Shutting down DomU does not return the display
>> to Dom0. The display remains at the last screen showing DomU shutting
>> down. Except for the shutting down phase, I've recorded the observations
>> in the first attachment.
>>
>> In the second scenario, Intel IGD is passed through to DomU. The ATI gfx
>> is thus absent. However, when DomU is booted, there is an IOMMU page
>> fault. This is shown in the second attachment starting from Line 659.
>> The system subsequently hangs. Does anyone have an explanation to what's
>> going on in this case?
>>
>> So, VGA passthrough works, but seems extremely flaky. Any
>> comments/suggestions to correct the problems observed will be greatly
>> appreciated.
>>
>> Thanks.
>>
>> - Beng Heng
> 
> 
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