Re: [Xen-devel] [PATCH] hvmloader / qemu-xen: Getting rid of resource conflict for OpRegion.

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

>> >> Let me just clarify that up to now we have been successful in passing
>> in
>> >> igfx cards without having to surface any of these ACPI bits. I was
>> just
>> >> mentioning that this is an inconsistency and might be worth
>> >> investigating at some point.
>>
>> So you are able to get a working win7 domU with IGD passthrough? That's
>> amazing.
>> Currently I just have a working linux domU with IGD passthrough. (just
>> solve the last known functionality issue)
>> But the win7 domU keeps BSOD during early boot stage with IGD passed
>> through.
>> The BSOD varies time to time, with or without intel gfx driver
>> installed.
>> But all the BSODs are more or less related to memory corruption.
>> I begun to suspect this may have something to do with the bios /
>> firmware.
>> (Your working system are based on intel board, right? Mine are Asrock
>> H77m-itx)
>> But I don't have enough knowledge to triage the issue (all I can do so
>> far is to analyze core dump with KDB).
>
> Hmm, I found a similar issue with BSODs like this and I tacked it down to the 
> Windows igfx drivers expecting to find vendor capabilities in the GMCH device 
> (the root device at 00:00.0). It was actually looking there for capabilities 
> specific to the gfx card. We fixed this by patching qemu to pass in the 
> vendor capabilities on that device. I am not sure if that made it upstream - 
> I will have to check.

Great news to hear. It'll be great if you can locate that patch for me.
I'm not sure which upstream you are referring to?
I'm using the qemu-xen 4.2.1 version. I remember the upstream qemu
does not support gfx-passthrough.

>
>>
>> I'll start a separate thread about this and keep this thread focused.
>> Help you could give me some hint in that thread.
>
> What is the separate thread going to be for? I did not see it.
>
Sorry, I was just back from a vacation, will pick this up soon.

>> Ross, your help is highly appreciated. I think it's not you that
>> confused things.
>> The problem comes from my side, I'm far from familiar with all these
>> ACPI / BIOS related stuff.
>> I dumped && disassembled the ACPI table. But have no idea how to read
>> the output...
>> I attached the DSDT.dsl dumped from my system, in case you would like
>> to take a quick check.
>>
>> Just one more question -- is the layout specific to the bios, or common?
>> I wonder how can we judge the security risk if the layout is not
>> constant.
>
> I would say the layout of the IGD stuff is common per the Intel spec for it 
> and the OEMs have to follow that spec when writing the BIOS. But it could 
> change for newer hardware (with a new rev of the spec for example that 
> extended the IGD functionality).
>

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