Developer workstation on laptop - no output to external monitor

[Gutter]

Hello everyone, I have recently installed promox ve in a laptop to be used as a developer workstation. I have somehow managed to set it up, installed debian xfce, created a couple of vms which I am accessing via SPICE and did a GPU passthrough.
However, I am not managing to output proxmox to an external monitor - I wanted to output both proxmox and the vms to the external monitor via the hdmi port instead of using the laptop monitor. Only the vms are shown on the external monitor.
So far I have tried the few solutions on this topic that I came across in this forum but none worked. I also disconnected the laptop display cable to force the output to the external monitor but it didn't work either.
What are the options I have to output both proxmox and vms to an external monitor? I attached my grub configuration. Thanks.

 

[BobhWasatch]

You can't both pass through the GPU to a VM and also use it on the host.

ETA: You might have one of those dual-GPU laptops where there is one built in to the CPU and there is also a discrete one. The way those usually work is the discrete GPU controls what goes out the HDMI port. If it is not enabled, the embedded GPU can use the port, but if it is enabled it takes over. So you _might_ be able to switch the port from the VM, but I'm doubtful since the embedded GPU isn't visible in the VM.

 

[Gutter]

Thanks for the reply. I don't necessarily need the single GPU available in the guest so it could stay in the host. Before doing the GPU passthrough I actually tried to have both the host and guest on the external monitor but I also couldn't get it to work. So I am right to assume that this setup is not possible, i.e. proxmox installed on a laptop with both host and guests displays only on a external monitor.

 

[BobhWasatch]

I am not clear on what you are trying to accomplish. What does it mean to have both host and guest on HDMI? Some kind of split-screen action? Being able to somehow switch back and forth like a virtual KVM?

What do you want to accomplish that you can't do by having the host on the HDMI and using SPICE to access the guest from the host? It kind of sounds like you are looking for a desktop virtualization product like VirtualBox.

 

[Gutter]

My laptop screen is slightly damaged and I want all video output to be made to an external monitor which is connected to the laptop HDMI port. Proxmox only shows on the laptop screen but the vms when started appear on the external monitor. I want both proxmox and vms to be shown on the external monitor.

 

[_gabriel]

if you passthrough gpu to guest, you loose your xfce of proxmox host because host cannot use gpu.
vm screen will be accessible only by spice ou noVNC.
once passthrough disable and gpu driver no blacklisted, xfce debian of your pve should be able to use external monitor.

 

[Gutter]

Thanks, it's clear now. The first answer in this thread nicely summarises that but only now it sunk in!

I will revert the GPU passthrough and give it another go - tried it before (prior to doing the GPU passthrough) and it didn't work but it could have been due to other issues.

But before I do this and forget about having the dGPU dedicated to the vm, would it be possible to isolate the iGPU to the proxmox host and the dGPU to the vms (as I have now by passthrough) and in this why have debian pve output to an external monitor? If so, how could I do this? (Apologies in advance if this doesn't make any sense!)

The graphic units I have in this laptop are as follows:

0000:00:02.0 VGA compatible controller [0300]: Intel Corporation TigerLake-H GT1 [UHD Graphics] [8086:9a60] (rev 01) (prog-if 00 [VGA controller])
0000:01:00.0 VGA compatible controller [0300]: NVIDIA Corporation TU117GLM [T1200 Laptop GPU] [10de:1fbc] (rev a1) (prog-if 00 [VGA controller])

 

[_gabriel]

iirc, external connector are only dGpu driven

 

[Gutter]

Right, I guess I will stay without GPU passthrough and have both pve and vms in the external monitor. Thanks for your answers.

Final one, the vms won't be used for gaming or anything too graphically demanding so not having the gpu performing as in bare metal I don't think it will make much of a difference for the intended use. However, I would like to have an idea on the loss of performance I can expect but couldn't find anything on this. Any ballpark estimate on the performance I am expected to lose without gpu passthrough?