What’s wrong with qemu/kvm?

stjohnswarts · on Oct 11, 2022

I find libvirtd to be fine other than sound when compared to virtualbox. I never did get sound to not be laggy and jerky in qemu on linux hosts.

Arnavion · on Oct 11, 2022

For a Linux guest, I just forward the host's pulseaudio socket over ssh.

    ssh -R /run/user/1000/pulse/native:/run/user/1000/pulse/native -X the-vm the-audio-using-command

I use this VM for occasional video watching and for video conferencing and haven't had any audio problems.

qalmakka · on Oct 11, 2022

This is a good hack, and it works better than a lot of alternatives, albeit Linux-on-Linux VMs have arguably few uses since systemd-nspawn exists (so you can just --bind the Pipewire socket in the VM)

dotancohen · on Oct 11, 2022

I'd say that Docker has replaced more Linux-on-Linux VMs than has systemd-nspawn. That said, I'm seriously interested in what GP is doing that he's forwarding audio. Maybe testing desktop distros? Circumventing DRM? Multiseating an office with thinclients?

qalmakka · on Oct 11, 2022

Docker is fine and dandy, but sometimes you just need to run an Ubuntu container that has to be persistent to run a few tests. debootstrap + systemd-nspawn -bD is amazing at that.

I am also curious about why GP needs audio in Linux VMs - I did similar tricks too but with Windows VMs, in order to pass-through my microphone to shoddy Windows-only corporate chat apps, but I never had the same necessity under Linux to be honest.

Arnavion · on Oct 11, 2022

>I am also curious about why GP needs audio in Linux VMs

$dayjob requires an Ubuntu installation with certain security characteristics and certain software installed. And I'm not going to install Ubuntu or do any of those other things to my actual machines :)

I also have a Docker container (well, podman container) of Ubuntu, for running closed-source applications like Discord and Steam. For that one I do indeed just volume-mount the PA socket instead of ssh-forwarding it.

qalmakka · on Oct 12, 2022

> And I'm not going to install Ubuntu [...] to my actual machines :)

Music to my ears. Life is too short to deal with Ubuntu.

imhoguy · on Oct 11, 2022

I moved from vbox to qemu/kvm. Windows UI was much faster on vbox thanks to its 3D acceleration solution. That is kind of translation layer which utilizes/shares your host GPU. I couldn't get such performance gains with qemu/kvm. Possibly it is available with dedicated GPU passed thru to the guest, but my laptop only has one GPU taken by the host.

ridgered4 · on Oct 11, 2022

This is indeed a real sore spot for qemu/kvm. VMware has good tech here as well.

One thing you may be able to do is use GVT-g to use a time slice of your Intel iGPU and pass that through. But it doesn't work on all Intel iGPUs and will never be available on newer Intel hardware.

imhoguy · on Oct 11, 2022

I have read a bit about SR-IOV and MxGPU of AMD, but they also seem to be not available in consumer grade Ryzen 7 laptops. So far I need Windows to do some minor MSVS dev or Edge web testing which is absolutely manageable with software emulation.