[Xen-users] Intel HD4000 IGD pass through appears to work, but monitor complains about 'no signal'

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

I've seen a recent report claiming that it works:
http://linux-bsd-sharing.blogspot.pt/2012/10/howto-xen-413-windows-8-hvm-domu-with.html
However, in my case, with a slightly different HW configuration the story is totally different. :-ï

My config:
HW: I7-3770 + AsRock H77M-ITX board
Dom0: Debian Wheezy stock xen (v4.1.3) + Debian stock kernel (3.2.x / 3.6.x) 64 bit version.

Note that both of us have only one gpu in the system. 
They difference is that the lucky guy has an  DQ77MK while mine is an AsRock. 
Another different is that he picks win 8 as domU, while my target is openelec 2.0, a linux 3.2.x based HTPC distro.

So basically what I can see is a functional domU, almost, I mean. 
It does not freeze / lock up at all.
All the assigned devices (IGD, audio, USB) are recognized and appears to work.
I can hear sound from aplay, so audio is working.
I can see the mouse I attached through lsusb so it appears to work too -- but I can't 100% confident since I haven't seen the pointer moving on screen...
The IGD is shown in lspci properly and the vainfo tool shows that the HW codec is fine.
The Xorg.0.log shows that intel driver is properly loaded, EDID from panel is correctly obtained.
xrandr tool can show the connected output (I've tried both VGA1 / hdmi3). 
It appears that I can switch resolution or turn-off the display through xrandr without any error reported.
The only *little* :-) issue is that I can't see any output on monitor / TV. 
Both of them complain about no signal and go back to power saving.

Well, I'm totally confused about the current status I'm at and need your advice. 
Is there any thing I should do to diagnosis and root cause the problem? 
I'm new to xen so am not familiar about the xen style of debugging. 
Would like to provide any log as you believe beneficial.

Thanks,
Timothy
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