HP ProDesk 600 G3 problem with enabling passthro

[Yanks]

I am using PROXMOX 7.1-8 on HP ProDesk 600 G3 with i7-6700 Intel Procesor
After installation I enabled Virtualization options: VT-x VT-d in BIOS,
I follow steps from https://www.reddit.com/r/homelab/comments/b5xpua/the_ultimate_beginners_guide_to_gpu_passthrough/

...Grub, Modules, remapping, blacklisting, adding GPU to VFIO & many restarts...

I have:
dmesg | grep -e DMAR -e IOMMU
[ 0.009079] ACPI: DMAR 0x000000009BFBE000 0000A8 (v01 INTEL KBL 00000001 INTL 00000001)
[ 0.009120] ACPI: Reserving DMAR table memory at [mem 0x9bfbe000-0x9bfbe0a7]
[ 0.125463] DMAR: Host address width 39
[ 0.125464] DMAR: DRHD base: 0x000000fed90000 flags: 0x0
[ 0.125469] DMAR: dmar0: reg_base_addr fed90000 ver 1:0 cap 1c0000c40660462 ecap 7e3ff0505e
[ 0.125472] DMAR: DRHD base: 0x000000fed91000 flags: 0x1
[ 0.125476] DMAR: dmar1: reg_base_addr fed91000 ver 1:0 cap d2008c40660462 ecap f050da
[ 0.125478] DMAR: RMRR base: 0x0000009bc5a000 end: 0x0000009bc79fff
[ 0.125481] DMAR: RMRR base: 0x0000009e000000 end: 0x000000be7fffff
[ 0.125483] DMAR-IR: IOAPIC id 2 under DRHD base 0xfed91000 IOMMU 1
[ 0.125485] DMAR-IR: HPET id 0 under DRHD base 0xfed91000
[ 0.125487] DMAR-IR: Queued invalidation will be enabled to support x2apic and Intr-remapping.
[ 0.126963] DMAR-IR: Enabled IRQ remapping in x2apic mode

but nothing in directory /sys/kernel/iommu_groups/

Configured VM when starting said: Error: cannot prepare PCI pass-through, IOMMU not present

 

[Yanks]

Problem Solved, Differences beetween grub and systemd

 

[Bartsch Labs]

Problem Solved, Differences beetween grub and systemd

Could you describe what those differences were? I'm having the same problem on a HP ProDesk 400 G3.

Edit: Never mind. I figured out what you meant. The official documentation on PCI passthrough focuses on systems that boot with grub. Mine, like yours, boots with systemd boot. So the intel_iommu=on needs to be added to the first line of /etc/kernel/cmdline.