Passthrough Contention Problems with Console and Linux VM

chicagomed

Has anyone had success in making PCI passthrough work to a Linux Desktop VM (in particular Hyprland)?

I am getting very mixed results but generally a lot of issues where there seams to be Seat contention for my USB devices (keyboard/mouse) and my GPU vs the Console (Cirrus VGA Driver/Virtual Input Devices).

I've been working through a series of blacklist and priority settings (mostly ChatGPT generated sadly) but was wondering if there is a more standard approach to this that someone knows/has figured out.

I can't imagine it's as hard as I'm making it so hoping one of your experts can help me here as I'm brand new to XCPNG!

Thank you!

olivierlambert

Hi,

The virtual console is slow because of the Cirrus VGA driver. We have some changes in the pipes that might improve it. I'm adding @TeddyAstie in the convo so he could give you some test packages to see if it's better

chicagomed

@olivierlambert great thank you. I think there is a Git issue also I found today 744. Not directly related but also driver related where the VGA disable function doesn’t work.

I think if in whatever future driver implementation there can be some more control of how it binds it would be really helpful for these use cases.

Thank you!

olivierlambert

We'll release at some point an update where you could switch to a new VGA type (virtio-vga) which is a LOT faster and allow better resolutions for the VM console. We have test packages in the next days if you want to provide some feedback,

DustinB

@olivierlambert yes please

olivierlambert

@TeddyAstie will post them when he fixed some basic bugs

chicagomed

@olivierlambert yes happy to test as well thank you!

TeddyAstie

@DustinB said in Passthrough Contention Problems with Console and Linux VM:

@olivierlambert yes please

It's something we're still evaluating, and there are known bugs (including some for unknown reasons).
There are still rough edges, not everything works perfectly; but it's somewhat there.

What works (tested) :

UEFI guests (OVMF knows how to drive virtio-gpu devices)
Linux operating systems with virtio-gpu drivers
High resolutions

What doesn't work :

VGA compatibility mode doesn't work properly
- BIOS guests have no display at least at the beginning
- operating systems without virtio-gpu drivers may or may not work properly (e.g Windows without appropriate drivers), but that still wants to be tested
cursor integration is a bit limited in Xen Orchestra (may not match guest cursor icon); but at least you don't see duplicate cursors

To test it (not production ready)

# Download repo file for XCP-ng 8.3
wget https://koji.xcp-ng.org/repos/user/8/8.3/xcpng-users.repo -O /etc/yum.repos.d/xcpng-users.repo

yum update --enablerepo=xcp-ng-tae1

you should see virtiovga packages for QEMU and Xapi.

Then, you set virtio-vga for your VM.

xe vm-param-set uuid=GUEST_UUID platform:vga=virtio

(or vm-param-add depending on whether or not the parameter has been set previously)

Regarding Windows support; KVM VirtIO drivers provides a "virito-gpu DoD" which should work (tested with upstream Xen, but not yet with XCP-ng).

chicagomed

@TeddyAstie great will take a look this weekend. Is there anything in particular you want us to test / check out?

TeddyAstie

@chicagomed said in Passthrough Contention Problems with Console and Linux VM:

@TeddyAstie great will take a look this weekend. Is there anything in particular you want us to test / check out?

What works/doesn't work and overall performance.