Re: [Xen-devel] Need help to debug win7 BSOD on IGD passthrough

["G.R." <firemeteor@xxxxxxxxxxxxxxxxxxxxx>]

>>>
>> I did a quick grep in the list, it seems that Jean was trying to
>> submit the patch.
>> http://lists.xen.org/archives/html/xen-devel/2012-01/msg01129.html
>> http://lists.xen.org/archives/html/xen-devel/2012-01/msg01128.html
>>
>> I guess this is lost accidentally? I don't see obvious negative
>> feedback on the thread.
>> Adding Jean, and Stefano who reviewed the patch.
>>
>> Will try this out tomorrow. Hope the patch can work without big modification.
>>
>> Jean, do you remember if there are other related patches to make gfx
>> passthrough working with windows?
>> I would like to check if there are more missed.
>>
>
> Ho right I remember those patch, I thought they went in but I guess I was
> wrong. Have you tried intel vga passthrough with those patches, does that
> make any difference?
Haven't got chance yet. Will try it out this weekend to see how it behaves.

> Also you should try to remove the OpRegion patch all together and see
> if the system is more stable after that.
I started my xen journey with version 4.1.3, which does not have the
OpRegion patch.
But I don't think the windows domU is better with that version.

Currently the linux domU works just fine with the OpRegion patch.
So I don't believe this is causing issues. But anyway I'll give it a
shot if I can't solve it in other ways.

> How much RAM do you give to your guest? We were seeing random BSOD
> with the Windows driver when the guest had more than 4G of RAM.
> To play it safe you should use 3G for your guest.

Thanks for this hint. I don't remember the number and need to check it
out tonight.
Could you clarify if it will cause problem for exact 4GB of RAM?
It's not likely that I give it 4GB+, but 4GB is a possible number.

>
>>>>
>>>> But the fix you mention seems to be igfx driver specific.
>>>> But I also observe BSOD without it -- I guess the system run with
>>>> basic VGA driver in that case.
>>>> Is it the expected behavior?
>>>>
>>>> One more question: does the windows igfx passthrough rely on 1:1
>>>> mapping of MMIO bars?
>>>> According to tutorials, nvidia cards require such trick.
>>>> But it seems that igfx linux driver does not require this -- the lspci
>>>> output shows different memory region on dom0 vs domU.
>>>
>>> It sounds right that it doesn't need to be but I am not
>>> sure; maybe someone else can confirm.
>>>
>> Jean, do you happen to know if the igfx card rely on 1:1 MMIO bar
>> mapping to work on windows?
>
> The windows igfx driver doesn't require the bar to be 1:1, it requires the
> device to be at the same BDF though.

So it means that the gfx-passthrough config must be enabled. Thanks
for this info.

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