Setup Virtual Machine using GPU passthrough with LookingGlass, Audio and Input support

[tomsk]

Hello, is there any tutorial how to setup Virtual Machine (Windows 10) in Linux using GPU passthrough with LookingGlass, Audio and Input support?

I know how to create Virtual Machine using GPU passthrough, but I don’t know how to setup audio support and input support using Spice (I want low latency input --> gaming and I don’t want to have hardware KVM switch).

So I wonder if there is any ultimate tutorial which exaplains how to setup Looking Glass properly and audio / input support.

For Audio I want to get audio from VM guest to Host and from Host pass microphone to VM (guest).

[kriss120]

Windows KVM: Tips and tricks for audio and improving performance

Following are a few tips and tricks I found useful when setting up my Linux/Windows KVM system. I spent a good week getting performance very close to bare metal, and most of that was spent searching for solutions that were all spread around, so I decided I’d make a summary post of what I consider to probably be common issues. First things first, I will assume in this that you already got iommu working and that you already set up your Windows 10 KVM, it is booting and you already installed all the drivers like you would on a normal Windows installation. If this is not the case go and have a look at @GrayBoltWolf’s guide for setting up your KVM. The post may be from 2016, but the procedure is mostly the same, and works perfectly fine on Ubuntu 18.04. Now let’s get into it. AUDIO One of the first things you are likely to have problems with is audio. As of right now this does not necessarily have an easy fix, but the problem probably lies with libvirt not having the required permissions to plug into pulseaudio. There are a couple of ways to solve this, but the simplest way is to run libvirt as your user and not as root, and make sure that pulseaudio is also running as your user and not as root. To do this, simply edit /etc/libvirt/qemu.conf and uncomment the line with #user = "root" and change it to user = "$YOURUSER". You might also need to uncomment the following line in the same config file: nographics_allow_host_audio = 1. If you do edit the libvirt config, do remember to restart libvirtd service in systemd or reboot for the changes to take effect. Now if your system uses systemd, you can use systemctl enable --user pulseaudio to make sure pulseaudio is always running as your user. This might not be necessary. If you are still having trouble try adding the following to your VM settings by running $ sudo virsh edit YOURVM and adding the <qemu:commandline> like this: <domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'> . . . . <qemu…

For audio, I made this post a while ago, look at the audio section, it should help you get virtualized audio from the VM to the Host. Keep in mind there are some challenges with passing audio from the VM to the host by the virtualized audio devices, in terms of crackling audio and mismatches in frequencies, so you will have to experiment and troubleshoot a lot based on your particular setup and if it works or not for you.

If you are very lucky it will just work out of the box.

For passing input between devices, you can probably do something using the kvm qemu environment, but wound up using Synergy for this, since it allows me to have a nifty set of keyboard bindings to easily switch control between multiple VM’s and it works very smoothly. I think LookingGlass might also be capable of capturing the input and passing it through to the VM, but I have not used it yet since I have a dedicated monitor for the VM.

[tomsk]

Thank you, I heard about Synergy, but isn’t there input lag? Because it is going over network.

[kriss120]

I use localhost so it goes over the local NAT network setup for the VM and directly to the host since they are on the same machine. I haven’t noticed any input lag so far, though I haven’t tested it.

[tomsk]

I found this for mouse / keyboard sharing https://www.kraxel.org/blog/2016/04/linux-evdev-input-support-in-qemu-2-6/ do you have any experiences with it? It should have zero latency.

[kriss120]

No, but if it is part of qemu then it is probably a better solution than synergy.

[tomsk]

Yes, I haven’t tested it yet, I found more about it here https://passthroughpo.st/using-evdev-passthrough-seamless-vm-input/

That would be great if someone tested input lag on Synergy and on Evdev

UPDATE:
I just created very simple program for testing Input Lag, you can test Input Lag between SPICE / Evdev / Synergy / Baremetal, if there is any input lag at all.
Link: https://github.com/t0msk/InputLagTester