Enabling IOMMU in Proxmox VE 8 Kernel

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doremo

New Member
Apr 11, 2024
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Do we still need to manually enable IOMMU in the kernel for Proxmox VE 8 by setting intel_iommu=on and intel_iommu=pt?
 
leesteken said:
There is no such thing as intel_iommu=pt and yes intel_iommu=on is needed: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#qm_pci_passthrough

EDIT: And there are threads here about this twice a week, if you need more detailed information.
Click to expand...
I believe IOMMU is enabled by default on my Proxmox VE 8 system. I observed that the outputs of dmesg | grep -i iommu were identical before and after adding intel_iommu=on to the kernel parameters, indicating no change in the IOMMU settings.
 
doremo said:
I believe IOMMU is enabled by default on my Proxmox VE 8 system.
Click to expand...
That is only when you use an AMD CPU. What CPU and motherboard are you using?
doremo said:
I observed that the outputs of dmesg | grep -i iommu were identical before and after adding intel_iommu=on to the kernel parameters, indicating no change in the IOMMU settings.
Click to expand...
It is quite possible you added it in the wrong place (or VT-d is not enabled or not supported) and it did not make a change (or you are using an AMD CPU).
What is the output of cat /proc/cmdline and for d in /sys/kernel/iommu_groups/*/devices/*; do n=${d#*/iommu_groups/*}; n=${n%%/*}; printf 'IOMMU group %s ' "$n"; lspci -nns "${d##*/}"; done?

EDIT: Intel IOMMU was enabled by default on PVE 7 for a little while but it broke too many Intel systems and they reverted it back (and updated the manual years later).
 
Last edited:
leesteken said:
That is only when you use an AMD CPU. What CPU and motherboard are you using?

It is quite possible you added it in the wrong place (or VT-d is not enabled or not supported) and it did not make a change (or you are using an AMD CPU).
What is the output of cat /proc/cmdline and for d in /sys/kernel/iommu_groups/*/devices/*; do n=${d#*/iommu_groups/*}; n=${n%%/*}; printf 'IOMMU group %s ' "$n"; lspci -nns "${d##*/}"; done?

EDIT: Intel IOMMU was enabled by default on PVE 7 for a little while but it broke too many Intel systems and they reverted it back (and updated the manual years later).
Click to expand...
I am SI engineer so I know how to differential AMD and Intel, thanks
 
doremo said:
I am SI engineer so I know how to differential AMD and Intel, thanks
Click to expand...
I'm glad that IOMMU worked by default on your system but many people did need to select a motherboard and Intel CPU that supports VT-d, enable it in BIOS and add intel_iommu=on to the PVE8 kernel parameters before IOMMU works (as a search on this forum will show).
 
leesteken said:
That is only when you use an AMD CPU. What CPU and motherboard are you using?

It is quite possible you added it in the wrong place (or VT-d is not enabled or not supported) and it did not make a change (or you are using an AMD CPU).
What is the output of cat /proc/cmdline and for d in /sys/kernel/iommu_groups/*/devices/*; do n=${d#*/iommu_groups/*}; n=${n%%/*}; printf 'IOMMU group %s ' "$n"; lspci -nns "${d##*/}"; done?

EDIT: Intel IOMMU was enabled by default on PVE 7 for a little while but it broke too many Intel systems and they reverted it back (and updated the manual years later).
Click to expand...
root@pve:~# cat /proc/cmdline
for d in /sys/kernel/iommu_groups/*/devices/*; do
n=${d#*/iommu_groups/*}; n=${n%%/*};
printf 'IOMMU group %s ' "$n";
lspci -nns "${d##*/}";
done
initrd=\EFI\proxmox\6.5.13-5-pve\initrd.img-6.5.13-5-pve root=ZFS=rpool/ROOT/pve-1 boot=zfs
IOMMU group 0 0000:00:02.0 VGA compatible controller [0300]: Intel Corporation Raptor Lake-P [Iris Xe Graphics] [8086:a7a0] (rev 04)
IOMMU group 10 0000:00:16.0 Communication controller [0780]: Intel Corporation Alder Lake PCH HECI Controller [8086:51e0] (rev 01)
IOMMU group 10 0000:00:16.3 Serial controller [0700]: Intel Corporation Alder Lake AMT SOL Redirection [8086:51e3] (rev 01)
IOMMU group 11 0000:00:1c.0 PCI bridge [0604]: Intel Corporation Alder Lake-P PCH PCIe Root Port [8086:51bb] (rev 01)
IOMMU group 12 0000:00:1d.0 System peripheral [0880]: Intel Corporation RST VMD Managed Controller [8086:09ab]
IOMMU group 13 0000:00:1d.2 PCI bridge [0604]: Intel Corporation Device [8086:51b2] (rev 01)
IOMMU group 14 0000:00:1d.3 PCI bridge [0604]: Intel Corporation Device [8086:51b3] (rev 01)
IOMMU group 15 0000:00:1f.0 ISA bridge [0601]: Intel Corporation Raptor Lake LPC/eSPI Controller [8086:519d] (rev 01)
IOMMU group 15 0000:00:1f.3 Audio device [0403]: Intel Corporation Raptor Lake-P/U/H cAVS [8086:51ca] (rev 01)
IOMMU group 15 0000:00:1f.4 SMBus [0c05]: Intel Corporation Alder Lake PCH-P SMBus Host Controller [8086:51a3] (rev 01)
IOMMU group 15 0000:00:1f.5 Serial bus controller [0c80]: Intel Corporation Alder Lake-P PCH SPI Controller [8086:51a4] (rev 01)
IOMMU group 16 0000:01:00.0 PCI bridge [0604]: ASMedia Technology Inc. ASM1812 6-Port PCIe x4 Gen2 Packet Switch [1b21:1812] (rev 01)
IOMMU group 17 0000:02:00.0 PCI bridge [0604]: ASMedia Technology Inc. ASM1812 6-Port PCIe x4 Gen2 Packet Switch [1b21:1812] (rev 01)
IOMMU group 17 0000:03:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)
IOMMU group 18 0000:02:08.0 PCI bridge [0604]: ASMedia Technology Inc. ASM1812 6-Port PCIe x4 Gen2 Packet Switch [1b21:1812] (rev 01)
IOMMU group 18 0000:04:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)
IOMMU group 19 0000:02:0a.0 PCI bridge [0604]: ASMedia Technology Inc. ASM1812 6-Port PCIe x4 Gen2 Packet Switch [1b21:1812] (rev 01)
IOMMU group 19 0000:05:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)
IOMMU group 1 0000:00:00.0 Host bridge [0600]: Intel Corporation Device [8086:a706]
IOMMU group 20 0000:02:0b.0 PCI bridge [0604]: ASMedia Technology Inc. ASM1812 6-Port PCIe x4 Gen2 Packet Switch [1b21:1812] (rev 01)
IOMMU group 20 0000:06:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)
IOMMU group 21 0000:07:00.0 Ethernet controller [0200]: Intel Corporation Ethernet Controller X710 for 10GbE SFP+ [8086:1572] (rev 02)
IOMMU group 22 0000:07:00.1 Ethernet controller [0200]: Intel Corporation Ethernet Controller X710 for 10GbE SFP+ [8086:1572] (rev 02)
IOMMU group 23 0000:5c:00.0 Ethernet controller [0200]: Intel Corporation Ethernet Controller I226-V [8086:125c] (rev 04)
IOMMU group 24 0000:5d:00.0 Ethernet controller [0200]: Intel Corporation Ethernet Controller I226-LM [8086:125b] (rev 04)
IOMMU group 25 0000:5e:00.0 Network controller [0280]: MEDIATEK Corp. MT7922 802.11ax PCI Express Wireless Network Adapter [14c3:0616]
IOMMU group 2 0000:00:01.0 PCI bridge [0604]: Intel Corporation Device [8086:a70d]
IOMMU group 3 0000:00:06.0 System peripheral [0880]: Intel Corporation RST VMD Managed Controller [8086:09ab]
IOMMU group 4 0000:00:06.2 PCI bridge [0604]: Intel Corporation Device [8086:a73d]
IOMMU group 5 0000:00:07.0 PCI bridge [0604]: Intel Corporation Raptor Lake-P Thunderbolt 4 PCI Express Root Port [8086:a76e]
IOMMU group 6 0000:00:07.2 PCI bridge [0604]: Intel Corporation Raptor Lake-P Thunderbolt 4 PCI Express Root Port [8086:a72f]
IOMMU group 7 0000:00:0d.0 USB controller [0c03]: Intel Corporation Raptor Lake-P Thunderbolt 4 USB Controller [8086:a71e]
IOMMU group 7 0000:00:0d.2 USB controller [0c03]: Intel Corporation Raptor Lake-P Thunderbolt 4 NHI [8086:a73e]
IOMMU group 7 0000:00:0d.3 USB controller [0c03]: Intel Corporation Raptor Lake-P Thunderbolt 4 NHI [8086:a76d]
IOMMU group 8 0000:00:0e.0 RAID bus controller [0104]: Intel Corporation Volume Management Device NVMe RAID Controller Intel Corporation [8086:a77f]
IOMMU group 8 10000:e0:06.0 PCI bridge [0604]: Intel Corporation Raptor Lake PCIe 4.0 Graphics Port [8086:a74d]
IOMMU group 8 10000:e0:1c.0 System peripheral [0880]: Intel Corporation RST VMD Managed Controller [8086:09ab]
IOMMU group 8 10000:e0:1c.4 PCI bridge [0604]: Intel Corporation Device [8086:51bc] (rev 01)
IOMMU group 8 10000:e0:1d.0 PCI bridge [0604]: Intel Corporation Alder Lake PCI Express Root Port [8086:51b0] (rev 01)
IOMMU group 8 10000:e1:00.0 Non-Volatile memory controller [0108]: Phison Electronics Corporation PS5019-E19 PCIe4 NVMe Controller (DRAM-less) [1987:5019] (rev 01)
IOMMU group 8 10000:e2:00.0 Non-Volatile memory controller [0108]: Phison Electronics Corporation PS5019-E19 PCIe4 NVMe Controller (DRAM-less) [1987:5019] (rev 01)
IOMMU group 8 10000:e3:00.0 Non-Volatile memory controller [0108]: Phison Electronics Corporation PS5019-E19 PCIe4 NVMe Controller (DRAM-less) [1987:5019] (rev 01)
IOMMU group 9 0000:00:14.0 USB controller [0c03]: Intel Corporation Alder Lake PCH USB 3.2 xHCI Host Controller [8086:51ed] (rev 01)
IOMMU group 9 0000:00:14.2 RAM memory [0500]: Intel Corporation Alder Lake PCH Shared SRAM [8086:51ef] (rev 01)
 
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doremo said:
initrd=\EFI\proxmox\6.5.13-5-pve\initrd.img-6.5.13-5-pve root=ZFS=rpool/ROOT/pve-1 boot=zfs
IOMMU group 0 0000:00:02.0 VGA compatible controller [0300]: Intel Corporation Raptor Lake-P [Iris Xe Graphics] [8086:a7a0] (rev 04)
IOMMU group 10 0000:00:16.0 Communication controller [0780]: Intel Corporation Alder Lake PCH HECI Controller [8086:51e0] (rev 01)
IOMMU group 10 0000:00:16.3 Serial controller [0700]: Intel Corporation Alder Lake AMT SOL Redirection [8086:51e3] (rev 01)
IOMMU group 11 0000:00:1c.0 PCI bridge [0604]: Intel Corporation Alder Lake-P PCH PCIe Root Port [8086:51bb] (rev 01)
IOMMU group 12 0000:00:1d.0 System peripheral [0880]: Intel Corporation RST VMD Managed Controller [8086:09ab]
IOMMU group 13 0000:00:1d.2 PCI bridge [0604]: Intel Corporation Device [8086:51b2] (rev 01)
IOMMU group 14 0000:00:1d.3 PCI bridge [0604]: Intel Corporation Device [8086:51b3] (rev 01)
IOMMU group 15 0000:00:1f.0 ISA bridge [0601]: Intel Corporation Raptor Lake LPC/eSPI Controller [8086:519d] (rev 01)
IOMMU group 15 0000:00:1f.3 Audio device [0403]: Intel Corporation Raptor Lake-P/U/H cAVS [8086:51ca] (rev 01)
IOMMU group 15 0000:00:1f.4 SMBus [0c05]: Intel Corporation Alder Lake PCH-P SMBus Host Controller [8086:51a3] (rev 01)
IOMMU group 15 0000:00:1f.5 Serial bus controller [0c80]: Intel Corporation Alder Lake-P PCH SPI Controller [8086:51a4] (rev 01)
IOMMU group 16 0000:01:00.0 PCI bridge [0604]: ASMedia Technology Inc. ASM1812 6-Port PCIe x4 Gen2 Packet Switch [1b21:1812] (rev 01)
IOMMU group 17 0000:02:00.0 PCI bridge [0604]: ASMedia Technology Inc. ASM1812 6-Port PCIe x4 Gen2 Packet Switch [1b21:1812] (rev 01)
IOMMU group 17 0000:03:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)
IOMMU group 18 0000:02:08.0 PCI bridge [0604]: ASMedia Technology Inc. ASM1812 6-Port PCIe x4 Gen2 Packet Switch [1b21:1812] (rev 01)
IOMMU group 18 0000:04:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)
IOMMU group 19 0000:02:0a.0 PCI bridge [0604]: ASMedia Technology Inc. ASM1812 6-Port PCIe x4 Gen2 Packet Switch [1b21:1812] (rev 01)
IOMMU group 19 0000:05:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)
IOMMU group 1 0000:00:00.0 Host bridge [0600]: Intel Corporation Device [8086:a706]
IOMMU group 20 0000:02:0b.0 PCI bridge [0604]: ASMedia Technology Inc. ASM1812 6-Port PCIe x4 Gen2 Packet Switch [1b21:1812] (rev 01)
IOMMU group 20 0000:06:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)
IOMMU group 21 0000:07:00.0 Ethernet controller [0200]: Intel Corporation Ethernet Controller X710 for 10GbE SFP+ [8086:1572] (rev 02)
IOMMU group 22 0000:07:00.1 Ethernet controller [0200]: Intel Corporation Ethernet Controller X710 for 10GbE SFP+ [8086:1572] (rev 02)
IOMMU group 23 0000:5c:00.0 Ethernet controller [0200]: Intel Corporation Ethernet Controller I226-V [8086:125c] (rev 04)
IOMMU group 24 0000:5d:00.0 Ethernet controller [0200]: Intel Corporation Ethernet Controller I226-LM [8086:125b] (rev 04)
IOMMU group 25 0000:5e:00.0 Network controller [0280]: MEDIATEK Corp. MT7922 802.11ax PCI Express Wireless Network Adapter [14c3:0616]
IOMMU group 2 0000:00:01.0 PCI bridge [0604]: Intel Corporation Device [8086:a70d]
IOMMU group 3 0000:00:06.0 System peripheral [0880]: Intel Corporation RST VMD Managed Controller [8086:09ab]
IOMMU group 4 0000:00:06.2 PCI bridge [0604]: Intel Corporation Device [8086:a73d]
IOMMU group 5 0000:00:07.0 PCI bridge [0604]: Intel Corporation Raptor Lake-P Thunderbolt 4 PCI Express Root Port [8086:a76e]
IOMMU group 6 0000:00:07.2 PCI bridge [0604]: Intel Corporation Raptor Lake-P Thunderbolt 4 PCI Express Root Port [8086:a72f]
IOMMU group 7 0000:00:0d.0 USB controller [0c03]: Intel Corporation Raptor Lake-P Thunderbolt 4 USB Controller [8086:a71e]
IOMMU group 7 0000:00:0d.2 USB controller [0c03]: Intel Corporation Raptor Lake-P Thunderbolt 4 NHI [8086:a73e]
IOMMU group 7 0000:00:0d.3 USB controller [0c03]: Intel Corporation Raptor Lake-P Thunderbolt 4 NHI [8086:a76d]
IOMMU group 8 0000:00:0e.0 RAID bus controller [0104]: Intel Corporation Volume Management Device NVMe RAID Controller Intel Corporation [8086:a77f]
IOMMU group 8 10000:e0:06.0 PCI bridge [0604]: Intel Corporation Raptor Lake PCIe 4.0 Graphics Port [8086:a74d]
IOMMU group 8 10000:e0:1c.0 System peripheral [0880]: Intel Corporation RST VMD Managed Controller [8086:09ab]
IOMMU group 8 10000:e0:1c.4 PCI bridge [0604]: Intel Corporation Device [8086:51bc] (rev 01)
IOMMU group 8 10000:e0:1d.0 PCI bridge [0604]: Intel Corporation Alder Lake PCI Express Root Port [8086:51b0] (rev 01)
IOMMU group 8 10000:e1:00.0 Non-Volatile memory controller [0108]: Phison Electronics Corporation PS5019-E19 PCIe4 NVMe Controller (DRAM-less) [1987:5019] (rev 01)
IOMMU group 8 10000:e2:00.0 Non-Volatile memory controller [0108]: Phison Electronics Corporation PS5019-E19 PCIe4 NVMe Controller (DRAM-less) [1987:5019] (rev 01)
IOMMU group 8 10000:e3:00.0 Non-Volatile memory controller [0108]: Phison Electronics Corporation PS5019-E19 PCIe4 NVMe Controller (DRAM-less) [1987:5019] (rev 01)
IOMMU group 9 0000:00:14.0 USB controller [0c03]: Intel Corporation Alder Lake PCH USB 3.2 xHCI Host Controller [8086:51ed] (rev 01)
IOMMU group 9 0000:00:14.2 RAM memory [0500]: Intel Corporation Alder Lake PCH Shared SRAM [8086:51ef] (rev 01)
Click to expand...
Amazing! Did Proxmox enable intel_iommu by default again?!? And without updating the manual (again), after they recently changed it to:
For Intel CPUs, you also need to enable the IOMMU on the kernel command line kernels by adding:
intel_iommu=on
Click to expand...

EDIT: Just the other day people still needed to add intel_iommu to it to work: https://forum.proxmox.com/threads/iommu-groups-on-supermicro-x13sch-f.145392/post-655551
 
Last edited:
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