i915 pass-through: 'pipe error 0x00000880' ?

[celemine1gig]

Hi guys,

I have a Intel CoffeeLake system (i3-8300 on C246 chipset), with installed Proxmox VE 6.2 (latest update status) that I wanted to use with several containers and one VM with fully passed-through i915 graphics.
Found a setup, that is nearly fully working (vm conf excerpt):

...
hostpci0: 00:1f,pcie=1
hostpci1: 00:02,pcie=1,x-vga=1
machine: pc-q35-4.1   (<== if I set anything newer than '4.1', the display output will no longer work)
serial0: socket
vga: serial0
...

Now, that setup is already working pretty well, besides the following issue:
I have a Debian testing VM setup, that gets its syslog flooded to no end with "pipe error 0x00000880" error messages from i915.

I did some google searching and found the following bug report with a very similar, but not exactly the same error message:
https://bugs.freedesktop.org/show_bug.cgi?id=109099

Went ahead with the described workaround and rebuilt the Debian VM's kernel, with the mentioned code change in the "i915_drv.h" file, forcing the "intel_vtd_active" function to return "true".
With that, the errors are gone and it seems to work just fine.

Which is great, however, I was wondering:
- Is someone else is also experiencing this?
- Is it a already known issue?
- Why do I have to force the vt-d detection?

Thanks in advance for your comments.

Best regards,
Ingmar

 

[celemine1gig]

Could be, that I just found the explanation myself:
https://git.kernel.org/pub/scm/linu...3&id=8195400f7ea95399f721ad21f4d663a62c65036f

Edit: Mixed something up. This will need to find its way into the kernel of the desired guest Linux.
Edit 2: If I find the time, I'll try that as well for my Debian testing VM.

 

[celemine1gig]

And last update:
The patch from kernel org worked flawlessly on the 5.9.1 kernel of my debian testing VM.

 

[poxin]

I have an AsRock C246 with Coffee Lake as well, but I'm unable to even see any IOMMU groups in proxmox. Can you share what you have in grub and modules to get this working? I've tried seemingly every combination in the documentation.

 

[celemine1gig]

Tim, are you sure, that grub is even used?
Have a look at "/etc/kernel/cmdline", edit as required and then run "pve-efiboot-tool refresh". Besides, follow the usual how-tos.