Re: Windows 8 VGA Passthrough

[Gordan Bobic <gordan@bobich.net>]

On 10/27/2013 09:01 PM, John Wargo wrote:
> On 10/27/2013 02:35 PM, Gordan Bobic wrote:
>> On 10/27/2013 04:21 PM, John Wargo wrote:
>>> On 10/27/2013 09:27 AM, John Wargo wrote:
>>>> On 10/27/2013 04:30 AM, Gordan Bobic wrote:
>>>>> On 10/26/2013 09:58 PM, John Wargo wrote:
>>>>>> Geniuses,
>>>>>>
>>>>>> I've been trying to get VGA pass-through working on Windows 8,
>>>>>> however
>>>>>> I've been running into a few issues.
>>>>>> Currently I can get Windows 8 running flawlessly without VGA
>>>>>> pass-through, however I'm planning on using it for gaming, so this
>>>>>> wont
>>>>>> work.
>>>>>>
>>>>>> When I start windows 8, I am able to get past the install portion of
>>>>>> the
>>>>>> DVD, however it hangs on "Getting devices ready.. (n%)".
>>>>>>
>>>>>> Hardware Information :
>>>>>> AMD Fx6300
>>>>>> ASUS M5a99x evo r2.0
>>>>>> 16GB RAM
>>>>>> 6670 Radeon HD - Dom0
>>>>>> 7850 Radeon HD - Win8
>>>>>
>>>>> I have recently (recently as in over the past 48 hours) re-tried to
>>>>> get ATI VGA passthrough working, and the results are... interesting.
>>>>>
>>>>> HD4850 dom0 + HD7450 domU worked fine - or as fine as ATI passthrough
>>>>> ever seems to work (slowdown + white lines when dragging windows
>>>>> after a domU reboot). I am using XP64 domU so I can't eject the GPU
>>>>> (it says it is being used). But shutting down the domU, doing echo 1
>>>>> > reset for the GPU from dom0 (I don't know how this is implemented
>>>>> and whether it does anything) and then starting it up again sometimes
>>>>> recovers it. GPU-Z runs and reports the GPU correctly.
>>>>>
>>>>> HD4850 dom0 + HD7970 domU results in the entire host locking up as
>>>>> soon as the driver is loaded in domU. My solution is to swap the dom0
>>>>> GPU for an 8800GT, and the problem now doesn't occur. If I had to
>>>>> guess, BIOS on the HD7970 does something bizzare, finds the HD4850 on
>>>>> the bus, tries to do something to it, and ends up crashing the host.
>>>>> This could also be exacerbated by the fact that I have to run with
>>>>> relaxed checking and no PCI ACS due to NF200 bridges on my
>>>>> motherboard. Even so, however, GPU-Z crashes the domU and it's GPU
>>>>> _hard_ (but not the host, thankfully). It crashes it so hard, that
>>>>> the only cure is to reboot the host. Reseting the GPU via /sys/
>>>>> doesn't seem to do anything to help.
>>>>>
>>>>> Are you using gfx_passthru=1 in your config? The way most people have
>>>>> this kind of thing working is with gfx_passthru=0, i.e. secondary
>>>>> passthru. Don't assign the PCI device in the config when installing.
>>>>> Once the domU install is complete, shut it down, and add the GPU you
>>>>> want to pass through. Then fire up domU in VNC, install the driver,
>>>>> and with a bit of luck it will come up with output on the external
>>>>> monitor.
>>>>>
>>>>> Also make sure that radeon or radeonfb kernel drivers DO NOT load
>>>>> before the device is assigned to xen-pciback. The exact way to ensure
>>>>> this will depend on what distro and dom0 kernel you are using.
>>>>>
>>>>> Gordan
>>>> Status update:
>>>>
>>>> The catalyst drivers appear to be working perfectly fine, device
>>>> manager shows no errors, and everything works great, except that when
>>>> I plug my monitor into the second card, I get "No Signal" on the
>>>> monitor, then it shuts off.
>>>>
>>>> I though that secondary passthrough meant that it would pass the
>>>> virtual adapter in as primary, but I could use my GPU that I passed
>>>> through, so where am I wrong, and how do I do that?
>>>>
>>>> -John
>>> I've been doing some research into my VGA passthrough, so I've gone
>>> through the various debugging steps, and the only thing that I've found
>>> out of place is with "xl dmesg" (attached).
>>>
>>> Where do I go from here?
>>
>> Sounds like your IOMMU may be buggy. You may need to set permissive=1
>> on your xen-pciback module.
>>
>> I cannot remember if xl uses the same configuration, but for xm you
>> could try putting this in your /etc/xen/xend-config.sxp:
>> (pci-passthrough-strict-check no)
>> (pci-dev-assign-strict-check no)
>>
>> Gordan
>>
> Gordan,
>
> After a bit of research, I was able to activate permissive mode on xen,
> but I've got nothing, I'm still getting page faults.
>
> The page faults occur when the loading screen goes black (I'd assume
> when it's trying to pass to the GPU)
>
> I've also tried setting (pci_msitranslate=0, along with changing
> qemu=qemu-xen, but it doesn't help

The correct incantation you seek is to put this in the config:
device_model_version="qemu-xen-traditional"

Gordan