No IOMMU detected, please activate it.

Windows7ge

Member
Sep 12, 2019
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Hello, I'm running PROXMOX 7.1-7 on a Intel Xeon platform and I'm attempting to get hardware pass-through working.

I've enabled VT-d in the BIOS.
I've added intel_iommu=on to GRUB_CMDLINE_LINUX_DEFAULT
I've ran proxmox-boot-tool refresh

The system persists in telling me that IOMMU isn't enabled. I actually had this issue occur on another Xeon server of mine and I'm completely lost as to what's causing the problem.

Meanwhile I have an AMD based server and it's happily running many PCI_e devices in a VM on 7.1-4.

Any thoughts? For as much as I don't like picking sides I'd prefer my main hypervisor server to be Intel based but this is a deal breaker.
 

Stoiko Ivanov

Proxmox Staff Member
Staff member
May 2, 2018
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is 'intel_iommu=on' present in the output of `cat /proc/cmdline`?
* if yes - I would suggest to read through the journal since boot to see for any messages indicating why it could not be activated
* if not - I guess your system is not using ZFS on / and thus you need to run `update-grub` instead of `proxmox-boot-tool refresh`

I hope this helps!
 

Windows7ge

Member
Sep 12, 2019
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0
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is 'intel_iommu=on' present in the output of `cat /proc/cmdline`?
* if yes - I would suggest to read through the journal since boot to see for any messages indicating why it could not be activated
* if not - I guess your system is not using ZFS on / and thus you need to run `update-grub` instead of `proxmox-boot-tool refresh`

I hope this helps!
Looks like the answer is not (output of cat /proc/cmdline):
Code:
initrd=\EFI\proxmox\5.13.19-2-pve\initrd.img-5.13.19-2-pve root=ZFS=rpool/ROOT/pve-1 boot=zfs

I am running ZFS on the boot media. I have a ZFS Mirror configured on a pair of SSD's which PROXMOX boots from.

Also if I try to run update-grub anyways (which is what I'm used to) PROXMOX gives me warning messages:
Code:
W: This system is booted via proxmox-boot-tool:
W: Executing 'update-grub' directly does not update the correct configs!
W: Running: 'proxmox-boot-tool refresh'

Is there a way to force update-grub?
 
Last edited:

Stoiko Ivanov

Proxmox Staff Member
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May 2, 2018
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Windows7ge

Member
Sep 12, 2019
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ok - you're using ZFS on an UEFI system - meaning grub is not used for booting - systemd-boot is used instead
- you need to edit /etc/kernel/cmdline

see the reference documentation on the topic:
https://pve.proxmox.com/pve-docs/chapter-sysadmin.html#sysboot_edit_kernel_cmdline
Alright. I removed intel_iommu=on from GRUB.

I added intel_iommu=on to cmdline:
Code:
root=ZFS=rpool/ROOT/pve-1 boot=zfs
intel_iommu=on

Ran proxmox-boot-tool refresh

Rebooted the server.

Same error:
fcf23c9554a650d34b2d0c35d9e3e3ccbae4cbd3.png

Re-checking cat /proc/cmdline:
Code:
initrd=\EFI\proxmox\5.13.19-2-pve\initrd.img-5.13.19-2-pve root=ZFS=rpool/ROOT/pve-1 boot=zfs
 

Windows7ge

Member
Sep 12, 2019
20
0
6
27
this needs to be on the same line as the rest

Code:
root=ZFS=rpool/ROOT/pve-1 boot=zfs  intel_iommu=on
It looks like that did it. For both this server and the previous one with the same issue.

I'll run some experiments to really make sure it's working but otherwise it looks like the problem is solved.

I can't explain why but it still feels strange that suddenly there was a switch from /etc/default/grub to /etc/kernel/cmdline after updating the OS despite the fact the old OS setup and the new one are identically ZFS Mirrors.

Just something I'm going to have to remember should I run into this again. Thank you!
 

Stoiko Ivanov

Proxmox Staff Member
Staff member
May 2, 2018
6,848
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I can't explain why but it still feels strange that suddenly there was a switch from /etc/default/grub to /etc/kernel/cmdline after updating the OS despite the fact the old OS setup and the new one are identically ZFS Mirrors.
The change of boot-loaders for ZFS was done quite a while ago (with PVE 5.4 IIRC) - it was necessary since the ZFS implementation in grub does not support newer features - and quite a few users ended up with systems which could not boot

in any case - glad that worked out ;)
 

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