Me and my friend both use looking-glass to access our Windows 10 VMs, we all use virt-manager to configure our VMs. However, my friend’s setup does not require any external monitor connection. He has no HDMI cable/dongle connected to the GPU for VM, and yet, he’s been able to start VM and get looking glass to work just fine. My setup, on the other hand, stucks with looking glass splash screen if there is no HDMI cable connected to my GPU and monitor, looking-glass log only shows eglutil.c:35 | swapWithDamageInit | Using EGL_KHR_swap_buffers_with_damage and Starting session with no other errors. Does any of you using looking glass without HDMI cable/dongle? If so, how does that work?
My friend told me that he had never plug in HDMI to his 2nd GPU, and it just work. He said that he simply follow tutorial online, and never thought that he would need some sort of external monitor to get GPU output something before using looking glass. I could not find any solution online except installing a virtual monitor.
Here are the hardware spec of both computers( Mine vs My friend’s setup )
CPU : Xeon E5 2683v3 - AMD 5600x
Host OS : Archlinux LTS - Archlinux
Host GPU : NVIDIA GTX 970 - NVIDIA GTX 1060
GUEST OS : Windows 10 - Windows 10
GUEST GPU : NVIDIA GTX 1070 - NVIDIA GTX 1070 NVIDIA GTX970
My friend also told me that he’d used many different setups, GTX 450. 660, 960, 970, 1060 with different version of drivers, and they all worked. I will compare our VM xml after he send me his this weekend. I thought that a HDMI cable or dongle is a must until he sent me a video, starting up a vm and using looking glass directly without any connection on his 2nd GPU, to prove me wrong.
I’m not sure how your buddy did it, but when I was setting up, I needed to have a monitor connected to the guest VM or a display dongle. I bought an assortment of dongles on Amazon, some DP and some HDMI, and was able to use Custom Resolution Utility to enable to resolution/refresh I wanted, and my guest streams to my host, my steam deck, etc. Without something connected to the guest GPU, I would have hangs exactly like you get. I use an AMD GPU on the host and an Nvidia guest.
I have a GTX 750 ti that I use for pass through that doesn’t need a dongle either. It’s some sort of virtual monitor mode. I tried it with an RX580 and I needed the dongle.
I don’t remember how I set it up that way, but it’s much easier to boot the host since there is only 1 GPU that is plugged in.
Just an update
I spent some time this weekend checking my friend’s vm setup, but still can’t find anything special. I created a new vm trying to micmic his setup as close as possible, and I got some sort of output without hdmi plugged in, it looks like the screen before Windows login. But, it’s in wrong resolution and super lag, mouse and keyboard seems not working very well, I could not even hit enter to get login input.
We compared all our hardware and driver/application versions. I found out that my friend is actually passing though GTX970 instead of GTX1070, and he is using looking glass RC, but stable version worked for him too. I start to wonder if this is some GPU ROM thing that prevents gpu export image in headless mode. He said that he has some spare gpu that worked before without HDMI cable which I can borrow. I am hoping that he can try my GTX1070 on his setup if he’s not too busy this coming weekend.
@gee_one when you said some sort of virtual monitor mode, did you mean that you actually installed virtual display on Windows guest?
This is what it looks like. I have the NVidia software installed and it shows up as an wired/analog device. I just use this for doing my taxes and zoom calls so I don’t care about frame rate.
I think when I set it up, I originally started with the virtual display, then installed everything and set up the “2nd” monitor. Then removed the virtual display and restarted? It’s been a while since I messed with it. I think I am on LG B5.0.1.
@gee_one, thanks for sharing, that Wired Display seems to be the key to my problem.
I got GTX 960 from my friend, Looking Glass worked fine without HDMI cable/dongle connected, it also worked with my GTX 970. The first time I used looking glass to access my VM with those GPUs, the Windows 10 VM seems to create a Wired Display by itself. I can login and setup my preferred resolution and it will keep all the settings after reboot. It runs 4KHD 60fps on ufotest website without any issue.
My friend tried to pass through my GTX 1070, but he could not able to get looking glass worked without HDMI connected. He said that he saw the login screen, but his mouse and keyboard were not working, and VM seems to crash itself. He could not create a Virtual Display in Windows 10 manually. It seems that Microsoft remove that function after Windows 8.1.
I do not have another GTX 1070 or any GPU with newer architecture, so I have no idea if this is only My GTX 1070, or this happened to all NVIDIA GPUS with the same and newer architecture .
For now, I will just swap my GTX 970 and GTX1070 to get rid of my HDMI dongle.
i remember a thread on reddit where someone posted a tool and write up on how to use virtual monitor in windows without the need of dummy dongles. Especially if you want high res high refresh rate output.
Remember if you install that dummy driver you most certainly have to re
install windows to get rid of it.
And forget ever getting an output signal on the actual ports on the passed through GPU.
It might work at the start but after some time it will stop working for no apparent reason.
