why do "No Subscription" updates break IOMMU / PCI passthru?

[tiro_uspsss]

fresh install of latest PVE = working pci passthru.
disable enterprise repo, add no subscription, then open shell, 'apt update' & 'apt upgrade'.. reboot.. *boom*! IOMMU borked.
anyone else with same experience?


when I go to add hardware/pci device, at the top of the box that pops up, it says:

No IOMMU detected, please activate it.See Documentation for further information.

my testing was as such:
fresh PVE install - no updates, create two VMs, only difference being, one is q35, the other i440fx. I started up both with no added hardware; then shut down both. I then added pci device to the i440fx VM (SAS2008 HBA), booted up, worked fine. Then added Chelsio 10Gb SFP+ card, booted up again, also worked fine. Removed both PCI devices from i440fx VM.
Next I added the same devices, one by one, booting up after each add, for the q35 VM. All 100% working. I also decided to test a AMD HD5450 card, I successfully passed that thru to the q35 VM (I didn't test it with the i440fx VM).
Powered down both VMs, and deleted them.
Went to PVE shell & ran: apt update, apt upgrade. Restarted the host box.
Again, created two VMs, only difference, same as before.. now if I try to add a PCI device, I get that aforementioned error message.

 

[leesteken]

Never run apt upgrade. Proxmox needs at dist-upgrade! I also had enterprise (with paid subscription) updates break passthrough in the past. Passthrough is fragile by nature and kernel/driver updates can cause regressions or break work-arounds.

EDIT: No IOMMU is often caused by it being turned off in the BIOS, because of unexpected power loss or BIOS updates that coincide with reinstalling Proxmox.

 

[tiro_uspsss]

Never run apt upgrade. Proxmox needs at dist-upgrade! I also had enterprise (with paid subscription) updates break passthrough in the past. Passthrough is fragile by nature and kernel/driver updates can cause regressions or break work-arounds.

EDIT: No IOMMU is often caused by it being turned off in the BIOS, because of unexpected power loss or BIOS updates that coincide with reinstalling Proxmox.

definitely no BIOS update for this ancient mobo..
sooo.. how am I supposed to kep the host OS up to date, ie security updates etc, without breaking everything?

 

[leesteken]

definitely no BIOS update for this ancient mobo..
sooo.. how am I supposed to kep the host OS up to date, ie security updates etc, without breaking everything?

Read this forum, keep an eye on experiences with newer kernel versions, maybe get a subscription for support if it is really important to you (for making money for example).
Things break once in a while, but are also often fixed quickly. Did you make sure to run apt dist-upgrade?

Can you show your IOMMU groups (to make sure IOMMU is on or off) using for d in /sys/kernel/iommu_groups/*/devices/*; do n=${d#*/iommu_groups/*}; n=${n%%/*}; printf 'IOMMU group %s ' "$n"; lspci -nns "${d##*/}"; done? And share the output cat /proc/cmdline to see which settings are active for IOMMU?