[SOLVED] Another "No IOMMU detected", please help debug.

wingo

New Member
May 16, 2023
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Attempting PCI passthrough on Dell Optiplex 3040 Small Form Factor. The graphics card is GeForce GT 710 2GB.

CPU(s) 4 x Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz (1 Socket)
Kernel Version Linux 5.15.102-1-pve #1 SMP PVE 5.15.102-1 (2023-03-14T13:48Z)
PVE Manager Version pve-manager/7.4-3/9002ab8a

lspci shows:
Code:
01:00.0 VGA compatible controller: NVIDIA Corporation GK208B [GeForce GT 710] (rev a1)
01:00.1 Audio device: NVIDIA Corporation GK208 HDMI/DP Audio Controller (rev a1)

/etc/default/grup has:
Code:
GRUB_CMDLINE_LINUX_DEFAULT="quiet intel_iommu=on"
GRUB_CMDLINE_LINUX=""

/etc/modules has:
Code:
vfio
vfio_iommu_type1
vfio_pci
vfio_virqfd

Code:
root@pve0:~# cat /etc/modprobe.d/kvm.conf
options kvm ignore_msrs=1

root@pve0:~# cat /etc/modprobe.d/blacklist.conf
blacklist radeon
blacklist nouveau
blacklist nvidia

root@pve0:~# lspci -n -s 01:00
01:00.0 0300: 10de:128b (rev a1)
01:00.1 0403: 10de:0e0f (rev a1)

root@pve0:~# cat /etc/modprobe.d/vfio.conf
options vfio-pci ids=10de:128b,10de:0e0f disable_vga=1

After reboot, not showing: vfio-pci drivers ?

Code:
root@pve0:~# lspci -knn -s 01:00
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation GK208B [GeForce GT 710] [10de:128b] (rev a1)
        Subsystem: NVIDIA Corporation GK208B [GeForce GT 710] [10de:118b]
        Kernel modules: nvidiafb, nouveau
01:00.1 Audio device [0403]: NVIDIA Corporation GK208 HDMI/DP Audio Controller [10de:0e0f] (rev a1)
        Subsystem: NVIDIA Corporation GK208 HDMI/DP Audio Controller [10de:118b]
        Kernel driver in use: snd_hda_intel
        Kernel modules: snd_hda_intel

When trying to add PCI device to VM, the message "No IOMMU detected".

BIOS setting for Virtualization is on (all other containers without PCI passthrough are fine), but there is nothing in BIOS
about IOMMU.

Any ideas? Is this a motherboard IOMMU issue? Nothing in the docs that I see. Thanks.

Also:

Code:
root@pve0:~# dmesg | grep -e DMAR -e IOMMU
[    0.034340] DMAR: IOMMU enabled

But I understand that is apparently not what it looks like.
 
Last edited:
Code:
root@pve0:~# cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-5.15.102-1-pve root=/dev/mapper/pve-root ro quiet intel_iommu=on

Thanks for the reply. As stated, the only thing I can find in the bios is "Enable Intel Virtualization Technology", as
is shown in the picture that someone else took on their PC.
BIOS_screenshot_2023-07-08_08-18-50.png
I can't find any details about motherboard support.
 
Code:
root@pve0:~# cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-5.15.102-1-pve root=/dev/mapper/pve-root ro quiet intel_iommu=on
intel_iommu=on is active and your CPU supports it, so it must be the motherboard that does not enable VT-d.
Thanks for the reply. As stated, the only thing I can find in the bios is "Enable Intel Virtualization Technology", as
is shown in the picture that someone else took on their PC.
That looks like VT-x, not VT-d.
I can't find any details about motherboard support.
See if the manufacturer has a BIOS update or a support forum or helpdesk?
 
I called this solved. From the view of the BIOS settings on this machine and the view of BIOS settings on other Dell computers, I have come to the conclusion that this feature is not supported on the motherboard of the Optiplex 3040. I will search for something one step up in refurbished computers to get this working.
 
Last edited:
From a quick Google search, it looks like this system should support VT-d: [1] [2]; but not sure, if this system can come with different mainboards, with which the VT-d-support could differ.

As @leesteken said, I would make sure, that you are on the most recent bios/UEFI version and then look for: "VT for Direct I/O" or: "Intel Virtualization Technology for Direct I/O" or: "Virtualization for Direct I/O" or similar.

[1] https://www.dell.com/support/manual...uid=guid-50d00e06-502e-4575-83ee-8682f97bf667
[2] https://www.reddit.com/r/Proxmox/comments/10tqsem/dell_optiplex_304_vtd_not_working_for_passthrough
 
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